CL-1902-95_student-assignment_dans-vieux-indesign.indd Student assignments for CL-1902_053242 95-CL-1902_053242 © ConsuLab Educatech Inc, 2025. All rights reserved. Electromagnetism Trainer 400-6330 Zéphirin-Paquet St. Québec QC G2C 0M3 Canada consulab.com info@consulab.com Toll-free: +1 (800) 567-0791 USA: +1 (810) 222-4525 Canada: +1 (418) 688-9067 Fax: +1 (418) 843-3444 2 95-CL-1902 Table of Contents Table des matières Introduction 4 Teaching Modules 6 Instrumentation 8 Magnetism 12 Electromagnetism 15 Magnetic Field 15 Faraday’s Laws 18 Electromagnetic Solenoid 19 Self-inductance 20 Mutual Induction 21 Automotive Ignition System 22 Right Hand Rule 23 Understanding AC and DC 24 AC Generator Charging System 24 DC Generator 24 Alternator Charging System 27 Motor Operation 30 Module A-1 — Magnetism 33 SA-1 LEVEL 1 33 Exploring Magnetism 33 SA-2 LEVEL 2 35 Current and Magnetic Fields 35 SA-3 LEVEL 3 37 Faraday’s Laws in Coil Circuits 37 Module A-2 — Electromagnetism 39 SA-4 LEVEL 1 39 Reverse Polarity 39 SA-5 LEVEL 2 41 Electromagnetic Solenoid 41 400-6330 Zéphirin-Paquet St. Québec QC G2C 0M3 Canada consulab.com info@consulab.com Toll-free: +1 (800) 567-0791 USA: +1 (810) 222-4525 Canada: +1 (418) 688-9067 Fax: +1 (418) 843-3444 3 95-CL-1902 Table of contents SA-6 LEVEL 3 43 Solenoid/ Actuator 43 Module A-1 and Module A-2 Student Assessments 45 Module B-1 and module B-2 47 SA-7 LEVEL 1 47 Self-Inductance 47 SA-8 LEVEL 2 50 Exploring Coil Interaction 50 SA-9 LEVEL 3 53 Measuring Mutual Inductance 53 Module C — Automotive Ignition 55 SA-10 LEVEL 1 55 Center Core Behavior 55 SA-11 LEVEL 2 57 Polarity and Induction 57 SA-12 LEVEL 3 59 Magnetic Field Collapse E ect 59 Module B-1, B-2 and C Student Assessment 62 Module D — Right Hand Rule 66 SA-13 LEVEL 1 66 Applying Lenz’s Law 66 SA-14 LEVEL 2 67 Magnetic Field Orientation 67 SA-15 LEVEL 3 69 Determining Flux Direction 69 Module D Student Assessment 72 Module E — AC Generation 74 SA-16 LEVEL 1 74 Rotor Current Action 74 SA-17 LEVEL 2 76 Half-Wave Rectifi cation 76 SA-18 LEVEL 3 78 Full-Wave Rectifi cation 78 Module E Student Assessment 80 400-6330 Zéphirin-Paquet St. Québec QC G2C 0M3 Canada consulab.com info@consulab.com Toll-free: +1 (800) 567-0791 USA: +1 (810) 222-4525 Canada: +1 (418) 688-9067 Fax: +1 (418) 843-3444 4 © ConsuLab Educatech Inc, 2023. All rights reserved. No part of this work may be reproduced or transmitted in any form by any means, electronic, mechanical, including photocopying and recording, or by any information storage or retrieval system, without written permission from the publisher. Printed in Canada. The content of this manual is applicable to models 053242 and above. 95-CL-1902 Table of contents Module F-1 and module F-2 83 SA-19 LEVEL 1 83 F-1 Motor Operation (3 pages) 83 SA-20 LEVEL 2 86 Motor Design and Direction 86 SA-21 LEVEL 3 88 Motoras a Generator 88 Module F-1 and F-2 Students Assessments 92 Glossary 95 consulab.com info@consulab.com 5 95-CL-1902 Introduction Introduction The CL-1902_053242 Electromagnetism Trainer is designed to teach the principles of magnetism and electromagnetism to demonstrate magnetic fi elds (Flux, Flux Lines, Lines of Force), how they are generated, and what automotive com- ponents use these principles. This curriculum is designed for self-directed learning, allowing students to independently follow the material and master these principles. They will learn to build magnetic lines of force circuits for CL-1902 Modules A-1, A-2, B-1 and B-2, and to describe what takes place when current and voltage are applied to a coil of wire. Modules B-1, B-2, and C will allow students to learn about self and mutual inductance. Module D demonstrates a working model of the Right Hand Rule. This section explains what occurs when a magnet passes through a coil of wire, illustrating Michael Faraday’s Laws of Electromagnetic Induction. It establishes the connection between magnetism and the operation of solenoids, motors, and generators. Module E explores how electromagnetism produces current in an AC generator, while Module F allows students to investigate the principles behind electric motor operation. Introduction summary The CL-1902 Electromagnetism Trainer allows you to learn the principles of magnetism and electromagnetism, neces- sary for performing useful work in electric vehicule and electronic system applications. Through each module, you will be able to understand and observe: • Magnetic fi elds • Feeling the attraction and repel of magnetic fi elds • Self inductance and mutual inductance • Right Hand Rule • Faraday’s laws • The link between magnetism and the operation of solenoids, motors, and generators consulab.com info@consulab.com 6 95-CL-1902 Introduction CRI Intructional Strategies • Performance Objectives – A precise description of the expected outcomes and the criteria for evaluating them, clearly defi ning what learners need to master. • Contextual Teaching/Learning Media – Demonstrate completion of the learning objectives by constructing the 21 student assignments at 3 levels in Modules A to F along with group discussions, and other available material. • Criterion Referenced Testing – Evaluation of learning in terms of the knowledge/skills specifi ed in the learning ob- jectives. • Laboratory Experiences will be found through the completion of the 21 student assignments. Power Supply Adapter Rods Jumper Wires E F-2F-1 C B-2 B-1 D A-2 A-1 Magnetic Field Indicator Compass Power Supply unit Power Supply Adapter consulab.com info@consulab.com 7 95-CL-1902 Teaching Modules Teaching Modules Module A-1 : A coil of wire to demonstrate how a current carrying conductor creates a magnetic fi eld. The two ends of the coil are connected to the blue and yellow receptacles. Module A-2 : A coil of wire to demonstrate how a current carrying conductor creates a magnetic fi eld, wound in the opposite direction than that of A-1, to demonstrate how the direction of windings a ects the magnetic fi eld generated. The two ends of the coil are connected to the blue and yellow recepta- cles. Module B-1 : A single coil of wire with an open core. It is identical to Module A-2. The two ends of the coil are connected to the blue and yellow receptacles. There is a red and green diode connected between the two receptacles. The diodes are connected with opposite polarities. The diodes are used to show induced voltage polarities. Module B-2 : A single coil of wire with an open core. This module demonstrates mutual induction by showing how electricity is transferred from one coil to another using an iron core. B-2 has ½ the number of turns as B-1. There is a physical gap between B-1 & B-2. The two ends of the coil are connected to the blue and yellow receptacles. There is a red and green diode connected between the two receptacles. The diodes are connected with opposite polarities. Module C : Demonstrates the increase in induction e ciency when one coil is put within another and uses an iron core. Two coil’s of di erent number of turns with the left coil able to be moved back and forth inside the right coil. The two ends of each coil are connected to the blue and yellow recep- tacles. There is a red and green diode connected between each coil’s two receptacles. The di- odes are connected with opposite polarities. The left hand coil has several iron core rods located inside the core. consulab.com info@consulab.com 8 95-CL-1902 Teaching Modules Module D : Demonstrates how a current carrying conductor has a magnetic fi eld generated around it, shows the right-hand rule. Two permanent magnets are positioned between conductive non-magnetic rods. Another conductive non-magnetic movable shaft (axle) lays across the two rods on which two plastic wheels are mounted. One fi xed rod is connected to the yellow receptacle and the other is connected to the blue receptacle. Module E : A permanent magnet mounted on a shaft (rotor) that is able to be rotated by a hand wheel crank. A single coil of wire wound stationary but positioned near the rotor with its two ends connected to the blue and yellow receptacles. In addition, a single diode is mounted to the panel with its two ends connected to blue and yellow receptacles. The are four other diodes connected to form a rectifi er bridge (Wheat- stone) with two diode junctions connected to blue and yellow receptacles and two other diode junctions connected to red and black receptacles. This module is used to show AC output, full and half-wave rectifi cation. Module F-1 : F-1 is a DC motor with a single pair of commutated sections and one winding. A single coil of wire is wound around an armature (one segment) that can be rotated with a hand wheel crank. The two ends of the coil are each connected to a copper commutator segment mounted on the armature shaft. The segments are electrically insulated from each other. Two brushes ride on the copper commutator segments. Red and black wires are connected to the brushes which are connected to the blue and yellow receptacles. The brushes are mounted in a brush holder that allows manual adjustment of the brush position around the commutator. NOTE : There is a sliding coupler on the right side end of the armature shaft can that be posi- tioned to connect Modules F-1 and F-2 together. Align the fl at surface of both shafts before sliding coupler over. F-1 and F-2 can be either driven electrically, manually with a hand crank or can be coupled together. Module F-2 : F-2 is a DC motor with multiple pairs of commutated sections and many windings. Two coils of wire are wound at 90º around an armature (two segments) that can be rotated with a hand wheel crank. Each end of the two coils are connected to a copper commutator segment mounted on the armature shaft. There are a total of four commutator segments. The segments are electrically insulated from each other. The two brushes ride on the commutator against the four segments 90º to each other. Red and black wires are connected to the brushes which are connected to the blue and yellow receptacles. The brushes are mounted in a brush holder that is not adjustable. consulab.com info@consulab.com 9 95-CL-1902 Instrumentation Instrumentation 1. Master ON / OFF 2. Voltmeter 0-15V 3. Bipolar diode 4. 12V / 10V switch 5. Ammeter 0-3A 6. Galvanometer 7. Polarity switch 8. Circuit connection receptacle 9. LED Readout 10. Circuit connection receptacle 11. Power supply adapter and cord 11 1 2 3 4 10 9 8 7 6 5 consulab.com info@consulab.com 10 95-CL-1902 Instrumentation Voltmeter 0-15V – Ammeter 0-3A The power supply voltmeter and ammeter are internally connected to the output receptacles and no further connections are necessary. Galvanometer The galvanometer (micro-ammeter) must be electrically connected in a circuit using its blue and yel- low μA receptacles. It includes a magnetic fi eld viewer with smaller magnets encased to show pres- ence of magnetic fi eld. Bipolar Diode The bipolar diode must be electrically connected in a circuit using its blue and yellow receptacles. 12V / 10V Switch Choice of system voltage either 10 VDC or 12 VDC. Polarity Switch and LED Readouts Power supply + and – output polarities can be manually reversed by the operator. The power supply has a polarity switch which determines the positive and negative of the blue and yellow output receptacles. Yellow LED readouts will indicate the selected polarity. After a period of inactivity (approx. 30 minutes) with the trainer power supply turned on, the LED display window will begin to randomly display the below combination of displays. In this event, simply make an adjustment of polarity switch or cycle the power supply master power button to reset the system. LED Readouts SWITCH IN CENTER POSITION (INDICATES THE POWER SUPPLY IS ON) SWITCH IN LEFT POSITION SWITCH IN RIGHT POSITION The power supply has a POLARITY SWITCH which determines the positive and negative polarities of the blue and yellow output receptacles. Yellow LED readouts will indicator selected polarity. Polarity Switch Positions After a period of inactivity (approx. 30 minutes) with the trainer power supply turned on, the LED display window will begin to randomly display the above combination of displays. In this event, simply make an adjustment of polarity switch or cycle the power supply master power button to reset the system. consulab.com info@consulab.com 11 95-CL-1902 Instrumentation Compass A common compass is used to detect and indicate poles of magnetic fi elds. NOTE : The red arrow points to the earth’s NORTH pole (magnetic SOUTH pole). The compass is used on the trainer to indicate the magnetic NORTH and SOUTH poles of the module compo- nents and not the earth’s directional NORTH or SOUTH poles. Magnetic Field Indicator A series of small ferrous rods each held within a small captive compartment. The rods will be a ected by nearby magnetic fi elds when brought in close proximity to components on the trainer. Rods One 3 in (8 cm) x 1/2 in (1.25) permanent magnet rod One 5 in (12 cm) x 1/2 in (1.25) aluminum rod (non-ferrous) One 5 in (12 cm) x 1/2 in (1.25) steel rod (ferrous) Jumper Wires Two 32 in (81.3 cm) red wires Two 32 in (81.3 cm) black wires Earth’s North pole MAGNETIC FIELD INDICATOR – A series of small ferrous rods each held within a small captive compartment. The rods will be affected by nearby magnetic fields when brought in close proximity to components on the trainer. MAGNETIC FIELD INDICATOR – A series of small ferrous rods each held within a small captive compartment. The rods will be affected by nearby magnetic fields when brought in close proximity to components on the trainer. Ferrous rods consulab.com info@consulab.com 12 95-CL-1902 Theory Theory consulab.com info@consulab.com 13 95-CL-1902 Magnetism Magnetism In the 17th century, Sir William Gilbert proposed that the Earth functions as a giant magnet with distinct North and South poles. The concept of magnetism was fi rst observed in lodestone, a naturally magnetized mineral, and in the way iron-based metals responded to it. To demonstrate this, Gilbert carved a piece of lodestone (Figure 1) into a spherical shape and showed that when a compass was placed anywhere on its surface, the needle consistently pointed toward the sphere’s North Pole, just like the behavior of a compass on Earth. Lodestone is a naturally magnetized rock made of magnetite, which is an iron oxide mineral. It is ferromagnetic, meaning it can attract certain met- als. Lodestone was used to make the fi rst magnetic compasses, and its name means “leading stone.” When a lodestone is hung so it can move freely, it will turn and point toward Earth’s North Pole. In most materials, the magnetic poles of molecules are arranged randomly, so they don’t create a magnetic force. But in metals like iron, nickel, and cobalt, the molecules can line up so their north poles point one way and their south poles point the other way. This alignment makes the material magnetic. In lodestone, this alignment happens naturally, which is why it acts as a magnet. A magnetic fi eld as shown in Figure 2 is the space surrounding a magnet through which its external lines of force fl ow. The direction of these lines of force is determined by polarity. Every magnet (Figure 2) has a north and a south pole. Poles behave somewhat like electrical charges. Like poles repel; unlike poles attract (Figures 2 & 3). Inside the magnet it- self, its lines of force travel from south to north. In the space surrounding the magnet, the lines of force move from north to south, returning to the magnet’s southern pole. More lines of force create a stronger magnet. Figure 1 Lodestone Figure 2 The magnetic fi elds of several di erent magnets. The magnetic lines of force also called Flux lines or the magnetic fi eld are directional and exit from the North Pole and enter through the South Pole. consulab.com info@consulab.com 14 95-CL-1902 Magnetism A magnet (Figure 3) can be any object or device that attracts iron, steel, and other magnetic materials. There are 3 basic types of magnets : • Natural • Man-made • Electromagnets Magnetism provides a link between mechanical energy and electricity. Electricity and magnetism are linked because any electrical current fl owing through a conductor creates a magnetic fi eld. When this conductor is wound into a coil around an iron core, it becomes an electromagnet, or a temporary magnet whose strength depends on the amount of current and number of coil turns. Any conductor moving through a magnetic fi eld creates electrical current. Electricity creates magnetism and magnetism creates electricity. By the use of magnetism, an alternator converts some engine mechanical power to electromotive Force Potential (EMF). Going the other direction, magnetism allows a starter motor to convert electrical energy from the battery into mechanical power to crank the engine. All magnetism is basically electromagnetism in that it results from the kinetic energy of electrons. Whenever an electric current is fl owed through a conductor, a magnetic fi eld is created. When a bar shaped permanent magnet is freely sus- pended, the poles tend to point toward the north and south magnetic poles of the earth, like a compass. Figure 4 shows a magnetic fi eld that is made up of many invisible lines of force, called fl ux lines. These lines are called a magnetic fi eld, magnetic fl ux or magnetic lines of force. Magnetic fl ux can be compared to current. Flux lines are directional and EXIT from the North Pole and ENTER through the South Pole. Flux lines are concen- trated at the poles and spread out into the areas between the poles. Magnetic fl ux is the product of the average magnetic fi eld times the perpendicular area that it penetrates. Flux is used in the operation of solenoids and transformers. In an electric generator where the magnetic fi eld penetrates a rotating coil, the area used in defi ning the fl ux is the projection of the coil area onto the plane perpendicular to the magnetic fi eld. Flux density refers to the number of fl ux lines per unit area. A Gauss gauge can be used to measure a magnetic fi eld. A magnetic fi eld is a vector quantity because it has direction and magnitude. It shows the magnetic infl uence on moving electric charges, electrical currents, and magnetic materials. A permanent magnet’s magnetic fi eld pulls on magnetic materials such as iron, and attracts or repels other magnets depending on pole alignment. Figure 3 Magnet and Magnetism Figure 4 Magnetic Flux or Magnetic lines of Force surrounding a bar magnet consulab.com info@consulab.com 15 95-CL-1902 Magnetism Magnetism Summary • Flux lines are directional and exit from the magnet’s North Pole and enter through it’s South Pole. • Magnetic lines of fl ux surrounding a coil look like the ones surrounding a bar magnet. • Flux density or concentration builds the magnetic force. A powerful magnetic fi eld will exhibit a dense fl ux fi eld, whereas a weak magnetic fi eld will exhibit a low density fl ux fi eld. • Flux density is always greatest at the poles of a magnet. • Flux lines do not cross each other in a permanent magnet. • Flux lines facing the same direction attract while fl ux lines facing opposite directions tend to repel. consulab.com info@consulab.com 16 95-CL-1902 Electromagnetism Electromagnetism Magnetism can also be created by an electric current. In the early 19th century, it was discovered that current-carrying conductors were surrounded by a magnetic fi eld. Current fl owing through a conductor, such as copper wire, creates a magnetic fi eld around the wire. This e ect can be observed by passing a compass lengthwise over a copper wire through which current is fl owing as shown in Figure 5 fl owing from positive to negative. The needle will defl ect from its North-South orientation when this occurs. Current fl ow through a wire creates a magnetic fi eld around the wire. The greater the current fl ow the stronger the magnetic fi eld. This type of magnetism created in the space around a conductor by the current fl owing through it is called electromagnetism. The magnetic fi eld surrounding a straight, current-carrying conductor consists of several concentric cylinders of fl ux the length of the wire, Figure 6. The number of magnetic lines of force and how far they spread from the wire determine the strength of the magnetic fi eld. The higher the current fl ow through the wire, the stronger the magnetic fi eld will be. Electromagnetic Field Rules • Magnetic lines of force or magnetic fl ux does not move when the current fl owing through a conductor remains at a constant value. When current fl owing through a con- ductor increases, the magnetic lines of force will extend further away from the conductor. • As current fl ow increases, the magnitude and strength of magnetic lines of force increase. As current fl ow decreas- es, they decrease. • As wire length increases, the magnetic fi eld strength de- creases. Wire length is inversely related to magnetic fl ux. • In automotive electricity and magnetism, we follow the conventional current theory [bold], which fl ows from pos- itive (+) to negative (-) or ground. To fi nd the direction of magnetic fl ux lines, we use the right-hand rule [bold] (see Figure 7): Wrap your right hand around the current-car- rying wire with your thumb pointing in the direction of current fl ow. Your fi ngers will curl in the direction of the magnetic lines of force. Figure 5 Electromagnetism Magnetic Field + - Figure 6 Concentric circles of magnetic fl ux surrounding a straight current-carrying conductor, following conventional current fl ow from positive to negative.. Figure 7 Right Hand Rule for fi eld direction used with Conventional Current Theory consulab.com info@consulab.com 17 95-CL-1902 Electromagnetism In a car or truck, the magnetic fi eld around a conductor that’s straight may be strong enough to interfere with current fl ow in sensitive nearby circuits, but it’s not enough to do work. The wire must be looped into a coil to concentrate the magnetic fi eld. The more loops or turns in the coil, the stronger your magnetic fi eld. When you place a soft iron core into the looped coil, it becomes a strong electromagnet that can move things. For our study we will use the right hand rule to signify the direction of the magnetic lines of force. Although there is a Left-Hand Rule for electron fl ow (negative to positive), all assignments will use the Right-Hand Rule. Formula for Electromagnetic Fields As the current (I) increases, the magnetic fi eld (B) gets stronger. As the length (l) of the coiled wire increases, the magnetic fi eld increases. B = Magnetic fi eld strength (in Tesla, T) N = Number of turns in the coil µ = Permeability of the material (how easily it supports a magnetic fi eld) CL-1902 ELECTROMAG TRAINER 31 Right Hand Rule Figure 8 Right Hand Rule for field direction used with Conventional Flow Theory • In automotive electricity and magnetism, it is important to note at this point that we use the conventional theory of current positive to negative or ground (+ to -), we use the right-hand rule to determine the direction of the magnetic flux lines as shown in Figure 8. It states that if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direction of current flow (positive to negative), your curved fingers would point in the direction of the lines of force. In a car or truck, the magnetic field around a conductor that’s straight may be strong enough to interfere with current flow in sensitive nearby circuits, but it’s not enough to do work. The wire must be looped into a coil to concentrate the magnetic field. The more loops or turns in the coil, the stronger your magnetic field. When you place a soft iron core into the looped coil, it becomes a strong electromagnet that can move things. For our study we will use the right hand rule to signify the direction of the magnetic lines of force. There is also a Left-Hand Rule for the electron-flow theory that is negative to positive. We will be using the Right-Hand Rule in this module. Formula for Electromagnetic Fields 𝐵𝐵 = 𝜇𝜇! 𝑁𝑁 𝑙𝑙 𝐼𝐼 This magnetic field equation is only used to illustrate the relationship between the factors contributing to the magnetic field. • B = magnetic field strength in Tesla • N = number of turns in the coil • µ = this is a constant that represents permeability of the free space • L = Length of the coil wire in meters = Length of the coil wire in meters (m) CL-1902 ELECTROMAG TRAINER 31 Right Hand Rule Figure 8 Right Hand Rule for field direction used with Conventional Flow Theory • In automotive electricity and magnetism, it is important to note at this point that we use the conventional theory of current positive to negative or ground (+ to -), we use the right-hand rule to determine the direction of the magnetic flux lines as shown in Figure 8. It states that if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direction of current flow (positive to negative), your curved fingers would point in the direction of the lines of force. In a car or truck, the magnetic field around a conductor that’s straight may be strong enough to interfere with current flow in sensitive nearby circuits, but it’s not enough to do work. The wire must be looped into a coil to concentrate the magnetic field. The more loops or turns in the coil, the stronger your magnetic field. When you place a soft iron core into the looped coil, it becomes a strong electromagnet that can move things. For our study we will use the right hand rule to signify the direction of the magnetic lines of force. There is also a Left-Hand Rule for the electron-flow theory that is negative to positive. We will be using the Right-Hand Rule in this module. Formula for Electromagnetic Fields 𝐵𝐵 = 𝜇𝜇! 𝑁𝑁 𝑙𝑙 𝐼𝐼 This magnetic field equation is only used to illustrate the relationship between the factors contributing to the magnetic field. • B = magnetic field strength in Tesla • N = number of turns in the coil • µ = this is a constant that represents permeability of the free space • L = Length of the coil wire in meters = Current in amperes (A) What this means to us as technicians is that the number of turns in the coil and the current through the coil is directly proportional to the magnetic fi eld. So, if you increase the number of turn in the wire or increase the current, the magnet- ic fi eld gets stronger. Loop Conductor Bending the wire into a loop can strengthen the fi eld around a straight conductor. This happens because the magnetic fi elds from each part of the loop combine at the center, making the fi eld stronger (see Figure 8). The Right Hand Rule also applies to loop conductors. Coil Conductor If several loops of wire are made into a coil, the magnetic fl ux density is further strengthened. Flux lines around a coil are the same as the fl ux lines around a bar magnet (Figure 9). They exit from the North Pole and enter at the South Pole. Use the Right Hand Rule to determine the North Pole of a coil. Increasing the number of turns in the wire, by increasing the current through the coil, or both, can strengthen the magnetic fi eld of a coil. CL-1902 ELECTROMAG TRAINER 31 Right Hand Rule Figure 8 Right Hand Rule for field direction used with Conventional Flow Theory • In automotive electricity and magnetism, it is important to note at this point that we use the conventional theory of current positive to negative or ground (+ to -), we use the right-hand rule to determine the direction of the magnetic flux lines as shown in Figure 8. It states that if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direction of current flow (positive to negative), your curved fingers would point in the direction of the lines of force. In a car or truck, the magnetic field around a conductor that’s straight may be strong enough to interfere with current flow in sensitive nearby circuits, but it’s not enough to do work. The wire must be looped into a coil to concentrate the magnetic field. The more loops or turns in the coil, the stronger your magnetic field. When you place a soft iron core into the looped coil, it becomes a strong electromagnet that can move things. For our study we will use the right hand rule to signify the direction of the magnetic lines of force. There is also a Left-Hand Rule for the electron-flow theory that is negative to positive. We will be using the Right-Hand Rule in this module. Formula for Electromagnetic Fields 𝐵𝐵 = 𝜇𝜇! 𝑁𝑁 𝑙𝑙 𝐼𝐼 This magnetic field equation is only used to illustrate the relationship between the factors contributing to the magnetic field. • B = magnetic field strength in Tesla • N = number of turns in the coil • µ = this is a constant that represents permeability of the free space • L = Length of the coil wire in meters Figure 8 Loop Conductor Figure 9 Coil Conductor consulab.com info@consulab.com 18 95-CL-1902 Electromagnetism Electromagnets The way to strengthen the magnetic fi eld surrounding a current-carrying conductor is to add a soft iron core (Figure 10). Soft iron is very permeable, so magnetic fl ux lines pass through it easily. If a piece of iron is placed inside a coil conduc- tor, the fl ux lines concentrate in the iron core, rather than pass through the air. This concentration of force increases the strength of the magnetic fi eld inside the coil and these are called electromagnets. If several loops of wire are made into a coil, the magnetic fl ux density is further strengthened. Flux lines around a coil are the same as the fl ux lines around a bar magnet (Figure 11). The Right Hand Rule shows that the thumb points in the direction of current fl ow (from positive to negative), and the curled fi ngers indicate the direction of the magnetic fi eld. The magnetic lines of force, or fl ux, exits from the North Pole and enters at the South Pole. You can use the Right Hand Rule (Figure 12) to determine the north pole of a coil. When using the Right Hand Rule for Coils : You place your right hand over the coil, with your fi ngers wrapped around the coil in the direction of current fl ow from positive to negative. Your thumb will then point to the magnetic north of your electromagnet. Increasing the number of turns in the wire, by increasing the current through the coil, or both, can strengthen the magnetic fi eld of a coil. Figure 10 Electromagnets Figure 11 Magnetic fi eld is generated from B to B when current fl ows through the coil in the direc- tion of the magnetic fl ux. Figure 12 Right Hand Rule for Coils Thumb Points to North Pole Fingers Around Coil Form POS (+) to NEG (−) Current Flow consulab.com info@consulab.com 19 95-CL-1902 Faraday’s Laws Faraday’s Laws A magnetic fi eld can create an electric current in a conductor if either the conductor or the magnetic fi eld is moving. When a permanent magnet provides the fi eld, this process is called magnetic induction (Figure 13). Imagine a horseshoe magnet with its North Pole on one side and South Pole on the other. Place a steel railroad tie (acting as the conductor) between the poles, and connect a voltmeter with one lead to each end of the tie. If the tie stays still inside the magnetic fi eld, the voltmeter shows zero. There’s no voltage because nothing is moving. Now, shake the railroad tie back and forth inside the magnet’s fi eld. As the tie cuts through the magnetic lines of force, the voltmeter shows a voltage. That means current is fl owing! Stop moving the tie, and the current stops. The induced voltage and current can be increased by: • Moving the conductor faster through the magnetic fi eld. • Using more conductor strands (like a coil instead of one tie). • Using a stronger magnet. Electromagnetic Induction Faraday’s Laws This principle is exactly how generators and alternators in cars and trucks produce electricity. Inside an alternator, a magnetic fi eld rotates past coils of wire, cutting through magnetic lines of force and inducing, or creating, current, just like shaking the railroad tie in our example. This process follows Faraday’s Laws of Electromagnetic Induction, which state: • First Law: An EMF (voltage) is induced in a conductor whenever it cuts through magnetic lines of force. • Second Law: The magnitude of the induced EMF depends on the speed of motion, the number of conductors, and the strength of the magnetic fi eld. #1 #2Figure 13 Magnetic Induction consulab.com info@consulab.com 20 95-CL-1902 Electromagnetic Solenoid Electromagnetic Solenoid A solenoid (Figure 14) is a device that uses electromagnetism to produce motion in small, individually controlled back- and-forth movements. However, the typical solenoid produces a lot more holding force than a relay. That means it can do more than close electrical contacts, which is what a relay does. When current fl ows through a solenoid’s coil, electromagnetism pulls an iron core into the coil; when current stops fl ow- ing through the coil, the core returns to its base position. These back-and-forth movements of the core can be attached to a rod that is attached to a device like a door lock to move it in two di erent directions to lock and unlock a vehicle door. The Electromag CL-1902 Coil A-2 along with the steel rod can be used to demonstrate the operation of a solenoid ac- tuator (Figure 15 ) such as an automotive power door lock actuator. The A-2 Coils become electromagnetic coils when power is applied to it. A-1 could also be used to demonstrate this e ect but there is not enough room for the metal rod supplied to make the demonstration. Through the use of electromagnetism, the solenoid can draw in the metal rod in one direction and then in the other direction by reversing the polarity. No current - No magnetic fi eld Current fl owing — Coil has a magnetic fi eld similar to that of a bar magnet If the current switches direction so does the magnetic fi eld Figure 14 An electromagnetic solenoid is a cylindrical coil of wire acting as a magnet when carrying electric current. The polarity of the coil can be changed to create movement in the other direction AC generator Magnetic Field Line Produced by Current Figure 15 Solenoid Actuator consulab.com info@consulab.com 21 95-CL-1902 Self-inductance Self-inductance Self-inductance is the induction of an EMF in a circuit when the current in that circuit is varied, not constant. It resists or opposes the change of current fl owing through it. This occurs due to the self-induced EMF produced in the coil. Self-in- ductance is the induction of a voltage in a current-carrying wire. Lenz’s Law states that this self-induced voltage tends to oppose the current that produces it. If the current continues to increase, the second voltage opposes the increase. When the current stabilizes, the counter voltage is no longer induced because there are no more expanding fl ux lines (no relative motion). When current to the coil is shut o , the collapsing magnetic fl ux lines self-induce a voltage in the coil that tries to maintain the original current. The self-induced voltage opposes and slows down the decrease in the original current. The self-induced voltage that opposes the source voltage is called counterelectromotive force (CEMF) or a Back EMF. Just for reference, the equation for Self-Inductance is shown below : E = The EMF generated −L = Self-Inductance measured in Henrys I = change in current in coil t = change in elapsed time When current fl ows from a battery or alternator (Figure 15) through a coil, the coil builds a magnetic fi eld. If the current changes suddenly, such as when you turn the circuit o , the magnetic fi eld starts to collapse. Because of self-inductance, the coil resists this change by generating a back EMF, which pushes current in the same direction as before. Back EMF acts like inertia [bold] in a car: just as a car resists a sudden stop and keeps rolling forward, the coil resists a sudden change in current. This electrical “inertia” means work [bold] must be done against the back EMF to establish current, and that work is stored as magnetic potential energy [bold], later used to pull in the armature of an automotive solenoid. CL-1902 ELECTROMAG TRAINER 54 Self-Inductance Figure 16 Self-Inductance Self-inductance is the induction of an EMF in a circuit when the current in that circuit is varied not constant. It resists or opposes the change of current flowing through it. This occurs due to the self-induced EMF produced in the coil. Self-inductance is the induction of a voltage in a current-carrying wire. Lenz's Law states that this self-induced voltage tends to oppose the current that produces it. If the current continues to increase, the second voltage opposes the increase. When the current stabilizes, the counter voltage is no longer induced because there are no more expanding flux lines (no relative motion). When current to the coil is shut off, the collapsing magnetic flux lines self-induce a voltage in the coil that tries to maintain the original current. The self-induced voltage opposes and slows down the decrease in the original current. The self-induced voltage that opposes the source voltage is called Counterelectromotive force (CEMF) or a Back EMF. Just for reference, the equation for Self-Inductance is shown below 𝐸𝐸 = −𝐿𝐿 ΔI Δt • E = The EMF generated • -L = Self-Inductance measured in Henrys • I = change in current in coil • t = change in elapsed time Using the above formula as reference, current change from an Alternator or battery (Figure 16) between let’s say the time difference (t) remains constant the number of lines of force measured by a change in current (I) also remain constant. The result is no CEMF created in the coil during this time period. If the current is removed the battery current decreases between t1 and t2. As this current decreases, the magnetic flux lines created by the current also decreases. A CEMF is generated by electromagnetic induction in the coil, which prevents the magnetic flux created by the current from decreasing and the direction of the current due to this CEMF is the same as the EMF generated by the AC generator or battery current. The Back-EMF opposed any change in the current in a circuit. The self-inductance acts as inertia. So, work needs to be done against the Back-EMF in establishing the current. This work done is stored as magnetic potential energy to pull in the armature in an Automotive Solenoid. AC generator Magnetic fi eld line produced by current Figure 15 Solenoid Actuator consulab.com info@consulab.com 22 95-CL-1902 Mutual Induction Mutual Induction When two coils are brought in close proximity to each another the magnetic fi eld in one coil tends to link with the other coil. This generates a voltage within the second coil. This magnetic property of a coil which a ects or changes the voltage in another coil is called mutual induction. The changing current in the primary coil creates a changing magnetic fl ux through the secondary coil that leads to an induced EMF (electromotive force) in the secondary coil. Also, when two coils are close together and connected through a common iron core, energy may be transferred from one to the other through magnetic coupling (Figure 16). Mutual induction means that the expansion or collapse of the magnetic fi eld around one coil induces a voltage in the second coil. Usually, the two coils are wound on the same iron core. One coil winding can be connected to a battery through a switch and is the primary winding. The other coil winding is connected to an external circuit and is called the secondary winding. Mutual inductance is the principle upon which transformers and ignition coils are based. The posi- tions are in Figure 16 : 1. When the switch is open, there is no current in the primary winding. There is no magnetic fi eld and, therefore, no voltage in the secondary winding. 2. When the switch is closed, current is introduced and a magnetic fi eld builds up around both windings. The primary winding thus changes electrical energy from the battery into magnetic energy of the expanding fi eld. As the fi eld expands, it cuts across the secondary winding and induces a voltage in it. A meter connected to the secondary circuit shows current. 3. When the magnetic fi eld has expanded to its full strength, it remains steady as long as the same amount of current exists. The fl ux lines have stopped their cutting action. There is no relative motion and no voltage in the secondary winding, as shown on the meter. 4. When you open the switch, the primary current stops, and the magnetic fi eld collapses. As it collapses, the magnet- ic fl ux lines cut across the secondary winding, but in the opposite direction. This induces a secondary voltage with current in the opposite direction, as shown on the voltmeter. Just for reference, the equation for mutual inductance is shown below : E = EMF induced in the B-2 secondary coil −M = Mutual inductance measured in henrys IP = change in current in the primary coil t = change in elapsed time The size of a mutual induced EMF changes in proportion to the changes in current for the number of magnetic lines of force in the primary or B-1 coil in a unit of time. This is multiplied by a constant we will call –M that is determined by the number of windings on Coils B-1 and B-2 along with other factors such as the type of iron used in the steel rod and the orientation of both coils. This information is for reference only. The principle of mutual inductance is used with all trans- formers and the automotive ignition coil. Mutual Induction AC Figure 16 Mutual Induction (Shutterstock) CL-1902 ELECTROMAG TRAINER 69 4. When you open the switch, the primary current stops, and the magnetic field collapses. As it collapses, the magnetic flux lines cut across the secondary winding, but in the opposite direction. This induces a secondary voltage with current in the opposite direction, as shown on the voltmeter. Just for reference, the equation for Mutual-Inductance is shown below E = −𝑀𝑀 Δ𝐼𝐼" Δt • ES = EMF induced in the secondary Coil B2 • -M = Mutual-Inductance measured in Henrys • IP = change in current in the primary coil • t = change in elapsed time The size of a mutual induced EMF changes in proportion to the changes in current for the number of magnetic lines of force in the primary or B1 coil in a unit of time. This is multiplied by a constant we will call –M that is determined by the number of windings on Coils B1 and B2 along with other factors such as the type of iron used in the steel rod and the orientation of the 2 coils. This information is for reference only. The principle of Mutual Inductance is used with all transformers and the automotive ignition coil. AUTOMOTIVE IGNITION SYSTEM Figure 18 Points and Condenser Type Automotive Ignition System The automotive ignition system (Figure 18 works on the principles of electro-magnetic with the ignition coil, which is a step-up transformer operating on the principle of Mutual Inductance. consulab.com info@consulab.com 23 95-CL-1902 Automotive Ingnition System Automotive Ignition System An automotive ignition coil demonstrates mutual inductance because it uses two windings, primary and secondary, like a step-up transformer to boost voltage for the spark plugs. Ignition systems apply battery voltage to the ignition coil positive side and pulse the negative side to ground. When the coil negative lead is grounded, the primary (low voltage) circuit of the coil is complete and a magnetic fi eld is created by the coil windings. When the circuit is opened, the mag- netic fi eld collapses and induces a high voltage in the secondary winding of the ignition coil, which is used to generate a voltage great enough to bridge a gap across the spark plug electrodes creating a spark. The early ignition systems used a set of contact points to make and break the electrical connection to ground. Electronic ignition uses a sensor such as a pickup coil or Hall e ect switch to signal an electronic module to make and break the ignition coil primary side ground. When the ignition switch is turned on, voltage should be available at both the positive terminal and the negative termi- nals of the coil. The labeling of positive (+) and negative (−) of the coil indicates that the positive terminal is more pos- itive (closer to battery positive terminal) than the negative terminal of the coil. This is referred to as coil polarity. Coil polarity positive or negative is established by what direction the coil is wound to the left or to the right. The polarity of an ignition coil is determined by the direction of rotation of the coil windings. The correct polarity is then indicated on the primary terminals of the coil.When polarity is reversed, the spark must jump in the opposite direction, from the cooler ground electrode to the hotter center electrode. This is harder for electrons to do, so the ignition system needs about 40% more voltage to overcome that resistance and fi re the plug. The coil’s output voltage depends on the ratio of primary to secondary turns, and its winding direction sets the polarity of the terminals, so reversing the leads changes both polarity and spark direction. Ignition Coils The ignition coil creates a high voltage spark by electromagnetic induction. The principle of electro-magnetic induc- tion states that when a magnetic fi eld crosses or cuts across a conductor, a voltage is induced in that conductor. Some automotive ignition coils are true step-up transformers in which the primary and secondary windings are not electrically connected. Spark plug Ignition breaker points Ignition coil Figure 17 Automotive Ignition System) consulab.com info@consulab.com 24 95-CL-1902 Right Hand Rule Right Hand Rule In a conductor like the copper rails in Module D, the lines of force around the copper rails are circular. You can fi gure out the polarity of the lines of force around a conductor by using the Right Hand Rule (Figures 18 & 19) to determine the direction of the magnetic fl ux lines. It states that if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direction of current fl ow (positive to negative), your curved fi ngers would point in the direction of the lines of force. In automotive electricity and magnetism, it is important to note at this point that we use the conventional fl ow theory of current positive to negative or ground (+ to −). The magnetic fi eld around a conductor can be strong enough to perform useful work, such as activating an electric pow- er steering motor in a modern vehicle. To concentrate the magnetic fi eld, the wire can be looped into a coil. The more loops, the stronger the magnetic fi eld. When a soft iron core is inserted into the coil, it becomes a strong electromagnet that can move parts as in a solenoid. Figure 18 Right Hand Rule for fi eld direction used with Conventional Flow Theory Current Flow Magnetic Field + - Figure 19 Right Hand Rule for Magnetic Fields and Current Flow consulab.com info@consulab.com 25 95-CL-1902 AC Generator Charging System & DC Generator Understanding AC and DC Before diving into alternators, it’s important to understand AC and DC current. Alternating Current (AC) changes direc- tion rapidly, alternating between positive (+) and negative (–), while Direct Current (DC) fl ows steadily in one direction, from the positive (+) terminal to the negative (–) terminal. Most vehicle systems and batteries require DC, but alternators naturally produce AC. To make this usable, a rectifi er [bold] converts AC into DC for charging the battery and powering DC vehicle loads. A converter [bold] is used when you need to change one DC voltage level to another, like when step- ping 12V DC down to 5V DC for sensors or control modules. An inverter [bold] is used when AC power is needed from the vehicle’s DC system, like when supplying AC to drive an electric motor in a hybrid vehicle. AC Generator Charging System The alternator (Figure 20), also called an AC generator, is driven by the engine’s crankshaft through a belt to convert mechanical energy into electrical energy. Inside the alternator, the rotor is the rotating component that creates a mag- netic fi eld, and the stator is the stationary set of windings that acts as the conductor. As the rotor spins, its magnetic lines of force cut across the stator windings, inducing voltage through electromagnetic induction. This electrical energy keeps the battery charged and powers the vehicle’s electrical systems. • The name alternator comes from the alternating current (AC) it produces. • AC is converted to direct current (DC) by a diode bridge rectifi er [bold] so the battery can stay charged. • The alternator must produce enough electrical energy to recharge the battery and to supply vehicle loads. • The term stator means stationary because its windings do not move, unlike the armature in a DC generator. DC Generator To better understand the alternator, we will look at the early DC generator. It also uses the principle of electromagnetic induction to produce DC current as shown in Figure 21. When the magnetic lines of force crosses or cuts a conductor (wire loop), it induces a voltage in that conductor. The DC generator uses an iron core or laminated iron sheets to create an electromagnet. When current fl ows through this coil a magnetic fi eld or fl ux is created between the pole pieces. Permanent magnets could be used. Figure 20 Belt-driven Alternator Figure 21 DC Generator LAMINATED CORE FIELDLINE OF FORCE WIRE LOOP CARBON BRUSH SPLIT RING COMMUTATOR N S consulab.com info@consulab.com 26 95-CL-1902 DC Generator A single wire loop is shown in Figure 22 between the North and South Pole poles. When this wire loop is turned within a magnetic fi eld, it cuts the lines of force and a voltage is induced. When there is a complete circuit from the wire loop, current will fl ow. Rotor The wire loop is connected to a split ring called a commutator and carbon brushes pick-up electrical energy because the commutator (wire loop) rotates. Wires from the carbon brushes transfer the energy to the load circuit shown as a resistor in Figure 21. When the wire loop completes one full rotation the induced voltage would reverse itself and therefore the current would fl ow in the opposite direction (AC current) after the initial half-turn. To produce an output in one direction or polarity (DC current), the split-ring commutator is employed. During the second half-turn, the carbon brushes run on commutator segments opposite to the ones over which they slid for the fi rst half-turn keeping the same rotational direction. The output waveform isn’t a steady-level DC, but rises and falls to make a pattern called a pulsating DC. So, for complete 360° turn of the wire loop, two waveforms or a Sine wave is produced. The rotor winding (Figure 23) in an alternator creates a magnetic fi eld, replacing the magnetic windings used in a DC generator. Although the rotor poles keep a small amount of magnetism when not in use, it is too weak to produce volt- age. To strengthen the magnetic fi eld, an excitation or fi eld winding [bold] sends current through the rotor winding, and a voltage regulator controls this current by adding resistance. Inside the rotor winding is a soft iron core that becomes magnetized when current fl ows, causing the attached pole pieces to take on magnetic polarity. In brush-type alternators, current reaches the rotor winding through slip rings and brushes. The combination of the iron core and steel rotor halves improves the magnetic fi eld’s strength and permeability. Figure 22 DC generator Rotor Stator Figure 23 Alternator Rotor (Field Winding) consulab.com info@consulab.com 27 95-CL-1902 DC Generator Stator The stator in an alternator (Figure 24) is the stationary conductor that replaces the wire-loop commutator of a DC gener- ator. Its windings are laminated to prevent eddy currents in the iron core. Three conductors are wound onto a cylindrical laminated core and assembled as one piece called the stator, which does not rotate like a DC generator’s commutator. Each winding is formed into coils spaced evenly around the core, with as many coils as there are pairs of north and south rotor poles. In a brush-type alternator, carbon brushes ride on two slip rings [bold] and connect to a battery-sup- plied circuit that carries current to and from the stator. The brushes are housed in a holder, and the fi eld current typical- ly ranges from 1.5 to 3.0 amperes. Figure 24 Alternator Exploded View Showing Rotor and Stator Lock Nut Pulley D.E. Pulley D.E. Bearing Stator Grounded Plate 3-Phase Bridge Rectfi er Pos. Terminal to Battery 2-Pin Connector Neg. Battery Terminal End Cover Bearing Screw Voltage RegulatorRotor Field Coil Carbon Brushes Slip Rings Air Vents Mounting Screws consulab.com info@consulab.com 28 95-CL-1902 Alternator Charging System Alternator Charging System The alternator charging circuit (Figure 25) consists of a magnet rotating inside a fi xed-loop stator, or conductor. The al- ternating current produced in the conductor is rectifi ed by a single diode as in Half-Wave Rectifi cation or multiple diodes in Full-Wave Rectifi cation. In our exercises we did not cover voltage regulation. However, in an automotive alternator, the voltage regulator, limits the fi eld current and thus the alternator output voltage according to the demands of the electrical system. AC Current induces voltage in the stator by rotating magnetic fi eld inside the stationing stator conduc- tor. The greatest AC current output is produced when the rotor is parallel to stator with magnetic fi eld at right angles to stator. The rotor makes a ¼ revolution and is at right angles to stator with magnetic fi eld parallel to stator then the voltage changes to positive peak, then to negative peak, produceing sine wave voltage. The wave shape controlled by angle between magnet and conductor. The voltage regulator (Figure 26) adds resistance in series to the fi eld circuit though a mechanical regulator, an electronic regulator, or by the vehicle engine management computer. Stator Conductor Load Magnetic Field Figure 25 Operation based on rotation of magnetic fi eld inside a fi xed-loop conductor Voltage Regulator Figure 26 Voltage Regulation consulab.com info@consulab.com 29 95-CL-1902 Alternator Charging System Half-Wave Rectifi cation A half-wave rectifi er transforms AC to DC voltage (Figure 27). The half-wave rectifi er circuit used in our exercise con- tained only one diode for the rectifi cation. It is defi ned as a type of rectifi er that allows only one-half cycle of an AC voltage waveform to pass while blocking the other half cycle. Full-Wave Diode Rectifi er Bridge The alternator produces AC, which means the current fl ows in one direction and then reverses every half turn of the rotor. However, vehicle systems and the battery require DC, which fl ows in only one direction. To convert AC into DC, the charging system uses diodes. A full-wave rectifi er bridge [bold] uses multiple diodes arranged in a bridge to allow both halves of the AC wave to be converted into DC, providing a smoother and more e cient output for the battery and electrical systems. Figure 27 One Module E diode used as a half-wave rectifi er Figure 28 Four Module E diodes used in a full-wave rectifi er consulab.com info@consulab.com 30 95-CL-1902 Alternator Charging System A diode acts is a one-way switch or electrical valve. The diode blocks ½ of the AC voltage (Figure 29). The diode will allow current to fl ow from X to Y, shown in Frame A. In Frame B, the current cannot fl ow from Y to X because the diode blocks the current. The fi rst half of the current, from X to Y, was allowed to pass through diode and shown on the graph as ½ sine wave XY. The second half of current, from Y to X, was not allowed to pass through diode. It is not shown on the wave form because it never traveled through the circuit. When voltage reverses at start of next rotor revolution, current is again allowed through diode from XY. When you add additional diodes to the circuit, this allows more AC voltage to be rectifi ed to DC. In Frame A, current moves from X to Y. It travels from X, through Diode #2, through the load, through Diode #3, and back to Y. n Frame B, current moves from Y to X. It travels from Y, through Diode #4, through the load, through Diode #1, and back to X. The current will move through the load in the same direction because the AC has been rectifi ed to DC. The waveform at the bottom of Figure 29 shows the current output of an alternator with one conductor and 4 diodes. There is more current because all of the voltage has been rectifi ed. This is called full-wave rectifi cation. Time Vo lt ag e C ur re nt C U RR EN T FL O W GRAPH C U RR EN T FL O W Figure 29 Full-Wave Diode Bridge Rectifi er consulab.com info@consulab.com 31 95-CL-1902 Motor Operation Motor Operation The electromagnet (Figure 30) is created in a loop of wire that is placed between two electromagnetic poles. Motors work on principle of magnetic repulsion. This magnetic repulsion takes place when a straight loop wire conductor is located within a magnetic fi eld and current fl ows through that wire loop. This situation creates two separate magnetic fi elds. One produced by the magnet, (poles of the magnetic fi eld winding) and another produced by the current fl owing through the conductor. Figure 30 shows the magnet’s magnetic fi eld moving from the S-Pole to N-Pole and conductor’s magnetic fi eld fl owing around the conductor. The magnetic lines of force have a rubber band characteristic. The magnetic fl ux stretches and tries to shorten itself. There is a stronger magnetic fi eld on one side of the looped conductor with a very weak magnetic fi eld on the other side. Then the conductor is repulsed by a strong magnetic fi eld and turns toward the weaker magnetic fi eld. As current in the conductor (the motor armature) and the strength of the magnetic fi eld windings increase, the following e ects occur: • More lines of magnetism are created on the strong side. • A greater repulsive force acts on the conductor (armature). • The conductor pushes harder toward the weak side in an attempt to reach a balanced neutral position. • More electrical heat is generated. Key Components of the System • North (N) and South (S) magnetic poles. • Two halves of a split copper ring, called the commutator. • A conductor bent into a U-shape, with its ends connected to the ring halves. • Stationary brushes connected to a battery via cables. • The combination of the U-shaped conductor loop and the split copper ring is called the commutator because they rotate together. Together, they form the armature. Figure 30 Electric Motor Operation consulab.com info@consulab.com 32 95-CL-1902 Motor Operation Motor Speed The speed of a motor can be varied in 3 ways : • Varying supply voltage. • Varying fl ux, and varying current through the fi eld winding. • Varying armature voltage, and varying armature resistance. Automotive Motor Applications Understanding electromagnetism isn’t just theory,it’s the foundation for diagnosing and repairing modern vehicles. Every electric motor operates on these principles: current fl owing through windings creates a magnetic fi eld, which interacts with other magnetic fi elds to produce motion. This knowledge helps technicians identify why a motor works, or why it fails. When a motor slows down, overheats, or stops working, the root cause often relates to magnetic fi eld strength, current fl ow, or mechanical resistance. Recognizing these relationships makes troubleshooting faster and more accurate. Electric motors are everywhere in modern vehicles. The starter motor converts electrical energy into mechanical torque to crank the engine. Power window motors use small DC motors with gear reduction to move glass smoothly. Seat and mirror motors rely on reversible DC motors, where changing polarity reverses direction. Electronic throttle control motors precisely adjust the throttle plate for engine performance, while cooling fan motors regulate engine temperature. Even fuel pumps depend on strong magnetic fi elds to maintain proper fuel pressure. When these systems fail, under- standing how electromagnetism drives their operation is key to diagnosing the problem. Technicians apply this theory during diagnostics. For example, a starter motor that doesn’t turn may have worn brush- es or weak fi eld windings, reducing torque. Slow power windows often point to high resistance in the armature or dirty commutator surfaces. Excessive current draw can signal shorted windings or seized bearings, while intermittent op- eration may result from broken brush connections. Erratic throttle response can indicate poor fi eld current or sensor failure. These issues all trace back to the principles of magnetic force and current fl ow. Diagnostic Tips for Common Motor Problems • Measure Voltage and Current: Low voltage or high current draw points to resistance or shorted windings. • Inspect Brushes and Commutator: Worn brushes weaken the magnetic fi eld, causing slow or no movement. • Check for Heat Damage: Burnt smell or discoloration indicates excessive current and magnetic imbalance. • Use Scan Tools: Modern systems monitor motor current and position feedback to detect faults quickly. consulab.com info@consulab.com 33 95-CL-1902 Student Assignments Student Assignments NOTE : In several student assignments there are references made to using a DMM (Digital multimeter) for the measurement of micro-amps (uA). If your facility does not have a meter capable of measuring micro-amps, you may use a milli-amp scale realizing that the measured readings will be less accurate than when measuring micro-amps. For example : 500uA would display as 5mA, etc. Also, the CL-1902 is equipped with a Galvanometer which in itself is a micro-ammeter but without measuring capability. consulab.com info@consulab.com 34 95-CL-1902 Module A-1 — SA-1 LEVEL 1 Module A-1 — Magnetism SA-1 LEVEL 1 Exploring Magnetism Objective : Students will identify magnetic fl ux lines and polarity using magnets and visualize fi eld patterns, demonstrating understanding of basic magnetic principles. Material Required : Compass, 3” permanent magnet rod, pencil and sheet of paper. Explanation : A magnetic fi eld is made up of many invisible lines of force. These lines are called a Magnetic Field, Mag- netic Flux or Magnetic Lines of Force. Magnetic Flux can be compared to current. Flux lines are directional and EXIT from the North Pole and ENTER through the South Pole. Flux lines are concentrated at the poles of a permanent magnet and spread out into the areas between the poles. 1. Take a clean white sheet of paper and write an N on the LEFT for the North Pole and an S on the RIGHT for the South Pole. 2. Place the compass to the LEFT of the NORTH POLE of the permanent magnet rod. The compass needle will point to the North Pole. 3. Move the compass up and to the right just above the North Pole and the compass needle to rotate clockwise showing the presence of the magnetic fi eld around the magnet rod. 4. Continue to move the compass and you will see the needle rotate indicating the movement of the magnetic fi eld consulab.com info@consulab.com 35 95-CL-1902 Module A-1 — SA-1 LEVEL 1 5. Continued movement of the compass to just above the South Pole and Needle has rotated 180 degrees from the position in Step #3. 6. Move the compass to the right of the South Pole and the compass needle points to the South Pole. 7. Defi ne magnetism in your own words. How does it relate to the concept of a magnetic fi eld? 8. What are magnetic lines of force, and how do they indicate the direction of magnetic fl ux? 9. Based on your observations in the activity, explain why fl ux lines are described as exiting the North Pole and enter- ing the South Pole. Use correct terminology from the glossary in your answer. Conclusion This assignment demonstrates the complete movement of the magnetic fi eld around a permanent magnet. Flux lines are directional and EXIT from the North Pole and ENTER through the South Pole. Review information on Magnetism in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 36 95-CL-1902 Module A-1 — SA-2 LEVEL 2 SA-2 LEVEL 2 Current and Magnetic Fields Objective : Students will show how electric current through a conductor creates a magnetic fi eld and apply the Right- Hand Rule to predict fi eld direction. Material Required : Compass. 1. Connect the red positive lead from the Yellow receptacle of the power supply to the Yellow positive receptacle of the A-1 Coil. 2. Connect the Black negative lead from the Blue receptacle of the power supply to the Blue receptacle of the A-1 Coil. 3. Place the compass aside the A-1 Coil. The compass needle will NOT show the presence of a magnetic fi eld with the power o . 4. Place the voltage switch in the 12V position and place the polarity switch to the right for positive to negative current fl ow. Turn on the power. A-1A-1 consulab.com info@consulab.com 37 95-CL-1902 Module A-1 — SA-2 LEVEL 2 5. With the power on the Compass Needle points North and shows the presence of a magnetic fi eld. 6. Flip the Polarity Switch to the Left and the Compass Needle will point to the South. 7. What makes an electromagnet di erent from a permanent magnet? 8. What is the Right-Hand Rule, and how does it help predict the direc- tion of a magnetic fi eld around a conductor? 9. Based on your observations, describe how reversing polarity changes the magnetic fi eld direction. Use terms like 10. current fl ow, polarity, and magnetic fl ux in your answer. Conclusion Current-carrying conductors are surrounded by a magnetic fi eld. Current fl owing through a conductor such as copper wire creates a magnetic fi eld around the wire. This e ect was shown by placing a compass around a coil of wire as in A-1. The compass needle defl ected to the North showing the presence of a magnetic fi eld and if the polarity is reversed it will point to the south. Review information on Electromagnetism in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 38 95-CL-1902 Module A-1 — SA-3 LEVEL 3 SA-3 LEVEL 3 Faraday’s Laws in Coil Circuits Objective : Students will build a coil circuit and apply Faraday’s Law to observe how changing current a ects magnetic fi eld strength and induced voltage. Material Required : 3” permanent magnet rod. 1. Connect the red positive lead from the Blue receptacle of the Gal- vanometer to the Blue receptacle of the A-1 Coil. 2. Connect the Black negative lead from the Yellow receptacle of the Galvanometer to the Yellow receptacle of the A-1 Coil. 3. Slide the North Pole of the permanent magnet rod into the A-1 Coil. You will see the needle bump up showing current generated as the rod moves into the coil. 4. Leaving the magnet rod in the coil will generate a lot of magnetic fl ux but no current on the Galvanometer. The coil only produces current when there is a change in the magnetic fl ux. consulab.com info@consulab.com 39 95-CL-1902 Module A-1 — SA-3 LEVEL 3 5. When you pull the permanent magnet rod out of the coil, the needle will go negative with the opposite e ect. 6. When the magnet is left inside the coil without moving, what happens to the galvanometer reading? A. It shows a strong positive current B. It shows a strong negative current C. It shows no current D. It fl uctuates continuously 7. What did the experiment demonstrate about electromagnetic induction? Conclusion Currents are produced by changes in the magnetic fi eld. Review information on Faraday’s Laws in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 40 95-CL-1902 Module A-2 — SA-4 LEVEL 1 Module A-2 — Electromagnetism SA-4 LEVEL 1 Reverse Polarity Objective : Students will demonstrate that the polarity of a coil can be switched by reversing current fl ow, using Coil A1 and Coil A2. Material Required : Compass. Coil A-1 1. Connect the red positive lead from the Blue receptacle of the power supply to the Blue positive receptacle of Coil A-1. 2. Connect the Black negative lead from the Yellow receptacle of the power supply to the Yellow receptacle of Coil A-1. 3. The compass needle will point NORTH showing the presence of a magnetic fi eld. 4. Turn on the power and fl ip the toggle switch to the left selecting Positive to Negative power fl ow. 5. The compass needle will point NORTH showing the presence of a magnetic fi eld. Coil A-2 6. Connect the red positive lead from the Blue receptacle of the power supply to the Blue positive receptacle of Coil A-2. 7. Connect the Black negative lead from the Yellow receptacle of the power supply to the Yellow receptacle of Coil A-2. 8. Place the compass to the left of Coil A-2. 9. With the power still ON, slide the compass down in front of Coil A-2, the compass needle will ROTATE 180° and the needle will A-1A-1 A-2A-2 consulab.com info@consulab.com 41 95-CL-1902 Module A-2 — SA-4 LEVEL 1 point South on the Reverse polarity Coil A-2. 10. Side by Side A-1 vs A-2. 11. What happens to the compass needle when placed in front of Coil A-2 with reverse polarity? A. It points North B. It points South C. It does not move D. It spins continuously 12. The di erence between Coil A-1 and Coil A-2 is due to polarity. Conclusion Current-carrying conductors are surrounded by a magnetic fi eld. Current fl owing through a conductor such as copper wire creates a magnetic fi eld around the wire. This e ect was shown by placing a compass front of the coil of wire in A-2. The di erence between A-1 and A-2 is due to the reverse polarity of the Coil A-2, the compass needle defl ected to the SOUTH showing the presence of a magnetic fi eld in the opposite direction with the compass needle pointing South. A-2A-2A-1A-1 Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 42 95-CL-1902 Module A-2 — SA-5 LEVEL 2 SA-5 LEVEL 2 Electromagnetic Solenoid Objective : Students will operate an electromagnetic solenoid to illustrate how electrical energy creates mechanical motion for device actuation. Material Required : 5” Iron Rod and Ruler. 1. Master power switch o . 2. Polarity switch set in the center. 3. Voltage in the 12 volt position. 4. Connect the Red lead from the Blue receptacle of the power supply to the Blue receptacle of the Coil A-2. 5. Connect the Black lead from the Yellow receptacle of the power supply to the Yellow receptacle of the Coil A-2. 6. Turn on the master power switch. 7. Place the Iron Rod into the Coil A-2 as shown in the photo. 8. Place a ruler as shown so that a number on the ruler like 3 inches is aligned with the end of the iron rod. Push the rod to meet the mea- surement rod at the 3 inch mark. Polarity switch still in the neutral position. consulab.com info@consulab.com 43 95-CL-1902 Module A-2 — SA-5 LEVEL 2 9. Move the polarity switch to the LEFT to get Positive to Negative cur- rent fl ow. When you throw the polarity switch, the iron rod will move to the left ½ inch. 10. What happens to the iron rod when the polarity switch is moved to the LEFT? A. It moves 1/2 inch to the left B. It moves 1/2 inch to the right C. It It does not move D. It spins inside the coil 11. A reverse wound coil can act as an electromagnetic to move devices for mechanical action. 12. What does this experiment show about the relationship between electricity and mechanical movement? CONCLUSION A reverse wound coil can be an electromagentic solenoid to move devices for mechanical action. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 44 95-CL-1902 Module A-2 — SA-6 LEVEL 3 SA-6 LEVEL 3 Solenoid/ Actuator Objective : Students will explain and test how electromagnetic induction powers solenoids and actuators by applying voltage and observing movement. Material Required : 5” Iron Rod and Compass. 1. Connect the red lead from the Yellow power supply receptacle to the Yellow receptacle of Coil A-2. 2. Connect the black lead from the power supply Blue receptacle to the Blue receptacle of Coil A-2. 3. Insert the iron rod as shown in Coil A-2. Polarity switch to the right set positive to negative. 4. Turn on power, the rod will be moved to the left indicating the movement of an actuator for power door locks. 5. Turn o the power and set the Polarity switch to the left for nega- tive to positive fl ow. Insert the iron rod as shown in Coil A-2. 6. Turn on the power and the rod will be moved to the right. Rod moved to the left Rod moved to the right consulab.com info@consulab.com 45 95-CL-1902 Module A-2 — SA-6 LEVEL 3 7. Draw a simple diagram showing how electromagnetic induction moves the iron rod inside the coil. Label the coil, the iron rod, and indicate the direction of movement for both polarity settings. Then explain in one sentence how this principle is used in a vehicle actuator. 8. Changing the changes the direction of movement in an actuator. CONCLUSION You can use an electromagnetic solenoid to move devices for mechanical action. You can change the polarity to move the device in the opposite direction. Review information on Electromagnetic Solenoid in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 46 95-CL-1902 Module A-1 and Module A-2 Student Assessment Module A-1 and Module A-2 Student Assessments 1. Which statement best explains the relationship between electricity and magnetism? A. Electricity and magnetism are unrelated. B. Electricity creates magnetism, and changing magnetism can create electricity. C. Magnetism only exists in permanent magnets. D. Magnetism only exists when current fl ows in one direction. 2. Which of the following will NOT create a magnetic fi eld? A. A permanent magnet B. A coil with current fl owing through it C. A straight wire carrying current D. A coil with no current fl owing through it 3. What happens to the magnetic fi eld when the current in a coil is increased? A. The magnetic fi eld becomes weaker B. The magnetic fi eld disappears C. The magnetic fi eld changes direction D. The magnetic fi eld becomes stronger 4. When polarity is reversed in a solenoid actuator, what changes? A. The direction of the magnetic fi eld B. The strength of the magnetic fi eld C. The number of turns in the coil D. The voltage applied to the coil 5. The helps predict the direction of the magnetic fi eld around a current-carrying conductor. A. Faraday Law B. Left Hand Rule C. Right Hand Rule D. Instrument Cluster 6. Two technicians are explaining the connection between electricity and magnetism. Technician A says that any elec- trical current fl owing through a conductor creates a magnetic fi eld. Technician B says that electricity creates magne- tism and magnetism creates electricity. Who is right? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B consulab.com info@consulab.com 47 95-CL-1902 Module A-1 and Module A-2 Student Assessment 7. All of these can strengthen a magnetic fi eld, EXCEPT: A. Add a soft iron core in the center of the coil. B. Increase the number of turns in the wire. C. Increase the current. D. Decrease the current. 8. Match the component to its function : A. Solenoid Converts electrical energy into mechanical movement B. Alternator Generates electricity using electromagnetic induction C. Actuator Controls valves or locks using electromagnetic force Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 48 95-CL-1902 Module B-1 and module B-2 — SA-7 LEVEL 1 Module B-1 and module B-2 SA-7 LEVEL 1 Self-Inductance Objective : Students will observe how varying current in a circuit induces an EMF within the same coil to understand the concept of self-inductance. Material Required : DMM and Compass. 1. Connect the red lead from the Yellow power supply receptacle to the Yellow receptacle on Coil B-2. 2. Then connect the black lead from the power supply Blue recep- tacle to the Blue receptacle on Coil B-2. Also, you can connect a DMM set on DC volts to the positive and negative terminals of the B-2 Coil as an option for a later exercise. 3. Place the compass on top of Coil B-2 and turn on the Power switch. Polarity Switch to the right Positive to Negative current fl ow. As the current fl ows, the magnetic fl ux is created as its density increas- es. The compass needle will point North indicating a magnetic fi eld. If you use the right hand rule, the direction of the magnetic lines of force or fl ux causes the left side of the B-2 coil to be the North Pole. 4. Turn o the power switch and observe the compass. It will reverse positions and the left side of Coil B-2 coil now becomes the South pole. This is because the coil itself produces a magnetic fi eld that is in the opposite direction from the one created by the battery to prevent the fl ux density from increasing. This is based on Lentz’s Law : the direction of the electric current which is induced in a conductor by a changing magnetic fi eld is such that the magnetic fi eld created by the induced current opposes changes in the initial magnetic fi eld. An EMF is created and causes the current to fl ow in the opposite direction from battery current. This is called a CEMF (Counter Elec- tromotive Force) or Back-EMF. B-2B-2 consulab.com info@consulab.com 49 95-CL-1902 Module B-1 and module B-2 — SA-7 LEVEL 1 5. Connect a RED Lead from the Galvanometer YELLOW receptacle to the Yellow receptacle of the B2 Coil and connect a Black Lead from the Galvanometer BLUE receptacle to the B2 Coil BLUE receptacle. 6. Piggyback another RED lead from Module E (AC Generator) top YELLOW receptacle to the YELLOW receptacle of the B2 Coil and piggyback another BLACK lead from Module E (AC Generator) top BLUE receptacle to the BLUE receptacle of the B2 Coil. 7. Connect a DMM set on AC Volts to the YELLOW & BLUE receptacle of the Galvanometer, which was wired in parallel. 8. Use the hand crank of Module E generator to generate an AC current in the B-2 Coil in order to demonstrate Self-Induction. You should be able to generate about ½ volt AC (± 453 mV) as shown on the DMM. 9. When you stop the hand cranking of the AC Generator, the DMM will show the CEMF voltage momentarily at ± 4.5 mV. 10. Explain in your own words what self-inductance means. Include the role of EMF and Lenz’s Law in your explanation. 11. What best describes back electromotive force (back EMF)? A. A voltage that assists the source voltage to increase current fl ow B. A voltage induced in a coil that opposes the change in current C. A magnetic fi eld that accelerates fl ux density D. A force that converts electrical energy into mechanical energy consulab.com info@consulab.com 50 95-CL-1902 Module B-1 and module B-2 — SA-7 LEVEL 1 12. Self-inductance is critical in which of the following automotive components? A. Fuel injectors B. Brake pads C. Starter solenoids D. Spark plugs CONCLUSION Self-inductance is the induction of an EMF in a circuit when the current in that circuit is varied. It resists or opposes the change of current fl owing through it. This occurs due to the self-induced EMF produced in the coil. Self-inductance is the induction of a voltage in a current-carrying wire. Lenz’s Law states that this self-induced voltage tends to oppose the current that produces it. If the current continues to increase, the second voltage opposes the increase. When the current stabilizes, the counter voltage is no longer induced because there are no more expanding fl ux lines (no relative motion). When current to the coil is shut o , the collapsing magnetic fl ux lines self-induce a voltage in the coil that tries to maintain the original current. The self-induced voltage opposes and slows down the decrease in the original current. The self-induced voltage that opposes the source voltage is called Counterelectromotive force (CEMF) or a Back EMF. This Back-EMF opposes any change in the current in a circuit. The self-inductance acts as inertia. So, work needs to be done against the Back-EMF in establishing the current. This work done is stored as magnetic potential energy to pull in the armature in a Automotive Solenoid. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 51 95-CL-1902 Module B-1 and module B-2 — SA-8 LEVEL 2 SA-8 LEVEL 2 Exploring Coil Interaction Objective : Students will examine how changes in one coil a ect voltage and current in a secondary coil to explain the principle of mutual inductance. Material Required : DMM, 5” Iron Rod, Ruler and Compass. 1. Connect the red lead from the Yellow power supply receptacle to the Yellow receptacle on Coil B-2. 2. Connect the black lead from the power supply Blue receptacle to the Blue receptacle on Coil B-2. 3. Connect the red lead from the Galvanometer YELLOW receptacle to the YELLOW receptacle on the Coil B-1. 4. Then connect the black lead from the Galvanometer BLUE recepta- cle to the BLUE receptacle on the Coil B-1. 5. Connect the AC power cord to the Power Supply. 6. Insert the CL-1902 iron rod as shown in Coil B-2 until it just begins to enter the B-1 Coil. 7. Place a ruler right next to Coil B-2 to measure the rod movement as you turn on the power. 8. Place the Cl-1902 compass on top of the B-2 Coil and note the position of the RED arrow. 9. Turn on the Power Switch, the GREEN LED will turn on indicating power fl ow and the iron rod moves about ½ inch to the left be- ing pulled into the B-1 coil by the Mutual Induction magnetic fl ux created in B-1 by the B-2 coil. Note that the compass needle points South. B-2B-2 B-2B-2B-1B-1 consulab.com info@consulab.com 52 95-CL-1902 Module B-1 and module B-2 — SA-8 LEVEL 2 10. Turn o the Power switch and move the compass from the B-2 Coil to the B-1 Coil and note that the compass rotates to the North Pole from the South Pole indicating the presence of a CEMF (Counte- relectromotive force). 11. Compass needle pointing to the North Pole showing presence of a CEMF (Counterelectromotive force) in the B-2 Coil. 12. Note the change in μA on the Galvanometer. 13. Which statement best describes mutual inductance? A. A coil induces voltage in itself when current changes B. Two coils share the same magnetic fl ux without a ecting each other C. A changing magnetic fi eld in one coil induces voltage in an other coil D. A coil resists changes in its own current fl ow consulab.com info@consulab.com 53 95-CL-1902 Module B-1 and module B-2 — SA-8 LEVEL 2 14. Draw two coils (B-1 and B-2) with an iron rod between them. Show the direction of current in the primary coil and the induced fl ux linking the secondary coil.. In your sketch, clearly label these six terms: primary coil, secondary coil, magnetic fl ux lines, induced EMF, North Pole, South Pole. 15. Why does inserting an iron rod between the coils increase mutual inductance? Explain in simple terms. CONCLUSION Coil B-1 EMF created by the power supply. Coil B-2 EMF created by mutual induction. When two coils are brought in proximity with each other the magnetic fi eld in one of the coils tend to link with the other. This generates a voltage in the second coil. This property of a coil which a ects or changes the current and voltage in a secondary coil is called mutual inductance. The changing current in the primary coil creates a changing magnetic fl ux through the secondary coil that leads to an induced EMF in the secondary coil. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 54 95-CL-1902 Module B-1 and module B-2 — SA-9 LEVEL 3 SA-9 LEVEL 3 Measuring Mutual Inductance Objective : Students will use Coil B-1 and Coil B-2 to measure induced voltage and determine how energy transfers be- tween coils through mutual inductance. Material Required : 3” Bar Magnet, Ruler and Compass. 1. Connect the red lead from the YELLOW Galvanometer portal to the YELLOW receptacle on Coil B-2. Then connect the black lead from the Galvanometer BLUE receptacle to the BLUE receptacle on the B-2 Coil. 2. Connect the AC power cord to the Power Supply. 3. Insert the CL-1902 steel rod as shown in Coil B-1 and place the compass on top of the B-2 coil. 4. Turn on the power switch and the green LED will illuminate indi- cating current fl ow through the B-2 coil. A magnetic fl ux (Field) is created so the RIGHT side becomes the South pole as indicated on the compass and the steel rod is be pulled into the B-1 coil by the magnetic fi eld created in the B-1 Coil. 5. The B-2 primary coil magnetic fl ux crosses the secondary B-1 coil, where an EMF is generated in this B1 secondary coil and repels the magnetic fl ux of the B-2 primary coil. This is the generation of a CEMF (Counterelectromotive force) in Coil B-1. The moment the power is OFF the current fl owing through Coil B-2 becomes 0 and the magnetic fl ux decreases. Placing the compass on the B-1 coil when the power is turned o causes the compass needle to rotate to the North Pole. This prevents the B-2 Magnetic Flux from de- creasing. 6. The direction of the B1 EMF is the opposite to that of the B-2 Coil. The EMF causes the Galvanometer to show an increase in current. 7. How does self-inductance make an EMF, and how does mutual in- ductance make an EMF? Tell which coil the EMF appears in and use these words in your answer: magnetic fl ux, back EMF, polarity, coupling. consulab.com info@consulab.com 55 95-CL-1902 Module B-1 and module B-2 — SA-9 LEVEL 3 8. Which change gives the strongest mutual inductance between B-2 (primary) and B-1 (secondary)? Pick one and say why using terms: fl ux linkage and coupling. A. Increase distance between coils B. Remove the iron rod C. Line up the coils and insert the iron rod all the way D. Rotate B-1 90° to B-2 9. B-2 is ON and the iron rod is in place, but the B-1 galvanometer barely moves and the compass hardly changes. What is the most likely fault? Explain how “shorted turns,” “poor coupling,” or an “open coil” could cause this. Add one quick test to confi rm. CONCLUSION The B-2 primary coil magnetic fl ux crosses the secondary B-1 coil, where an EMF is generated in this B-1 secondary coil and repels the magnetic fl ux of the B-2 primary coil and generates a CEMF in the B-1 Coil. The moment the power is OFF the current fl owing through the B-2 Coil becomes 0 and the magnetic fl ux decreases. Placing the compass on the B-1 coil when the power is turned o causes the compass needle to rotate to the North Pole. This prevents the B-2 Mag- netic Flux from decreasing. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 56 95-CL-1902 Module C — SA-10 LEVEL 1 Module C — Automotive Ignition SA-10 LEVEL 1 Center Core Behavior Objective : Students will explore how the center core of a coil reacts to magnetic fi eld changes to determine how energy is stored and released. Material Required : Compass. 1. Connect the Red lead from the Blue power supply receptacle to the blue receptacle of Module C Primary Coil. 2. Connect the Black lead from the Yellow receptacle of the power supply to the Yellow receptacle of Module C Primary Coil. 3. With the polarity toggle switch in the center or neutral position turn on the power supply. The inner coil has a permanent iron multi core that is visible. 4. Turn the polarity toggle switch to the left and note what happens to the multi-core pieces when the toggle switch is moved. 5. Turn the polarity toggle switch to the right and note that the multi- core pieces have changed when the toggle switch is moved. Module C Primary Coil consulab.com info@consulab.com 57 95-CL-1902 Module C — SA-10 LEVEL 1 6. The action of the multi-core pieces demonstrates the magnetic fi eld or fl ux surrounding the primary core. 7. In your own words, explain why the multi-core pieces moved when the polarity changed. 8. Draw what you observed inside the coil when the polarity was switched. Label your drawing with magnetic fi eld, fl ux direction, iron core, North (N) pole, South (S) pole. 9. Which real-world device uses this principle to create high voltage? A. Automotive ignition coil B. Battery C. Light bulb D. Solar panel CONCLUSION The iron core of a C Module primary coil that would be part of a step-up transformer is greatly a ected by the magnet- ic fi eld surounding it and in the operation of an automotive ignition coil this is used to create enough voltage to jump a spark plug. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 58 95-CL-1902 Module C — SA-11 LEVEL 2 SA-11 LEVEL 2 Polarity and Induction Objective : Students will investigate how reversing polarity in the primary coil induces voltage in the secondary coil to understand mutual induction principles. Material Required : DMM, DSO (optional) and Compass. 1. Connect the Red lead from the Blue power supply receptacle to the blue receptacle of Module C inner (primary) coil. 2. Connect the Black lead from the Yellow receptacle of the power supply to the Yellow receptacle of Module C inner (primary) coil. 3. Connect a red lead from the Galvanometer Blue receptacle to the C outer (secondary) coil Blue receptacle. 4. Connect a black lead from the Galvanometer Yellow receptacle to the C outer (secondary) coil yellow receptacle. 5. Piggyback Connect Red Lead of a DMM from the μA port to the BLUE Receptacle of module C outer (secondary) coil. 6. Piggyback Black lead from the DMM common ground to YELLOW receptacle of C outer (secondary) coil. 7. Set the DMM to read μA on the 4,000 μA scale with Min-Max Record Max function. 8. Place the compass to the right of Module C outer (secondary) coil. 9. Turn on the power supply. The moment you move the polarity switch to the LEFT the RED LED (Light Emitting Diode), turns on which is connected to the C inner (primary) coil. The compass RED needle will point to the South. 10. Move the inner (primary) coil in & out of the outer (secondary) coil. DMM will register microamps. This exercise measured ± 508 μA. 11. Use the Min-Max Record function to capture average amperage. A DSO can also be used. The Galvanometer will also show an in- crease in current. CONCLUSION (Steps 5-11) : With the polarity switch in the LEFT position for Positive to Negative fl ow, the current fl owing through the primary coil decreases and will become 0. An EMF (Electromotive Force) is generated in the secondary coil in the direction that pre- vents a reduction of the magnetic fi eld in the primary coil as seen by the compass needle moving to the South. The RED LED is on due to the current created by the EMF and we are reading microamps on the DMM. consulab.com info@consulab.com 59 95-CL-1902 Module C — SA-11 LEVEL 2 12. With the same hook-up. Now move the polarity switch to the RIGHT and the Green LED will be on, which is connected to the inner (pri- mary) coil. The compass RED needle will point to the NORTH. 13. Move the inner (primary) coil in & out of the outer (secondary) and DMM will register microamps. This exercise measured ± 508 μA and it may be higher. 14. Use the Min-Max Record function to capture average amperage A DSO can also be used. The Galvanometer will also show an in- crease in current. CONCLUSION (Steps 12-14) : With the polarity switch in the RIGHT position for Negative to Positive fl ow, current is fl owing through the primary coil. A magentic fi eld was created in the primary coil as shown by the compass needle point NORTH. An EMF (Electromotive Force) is generated in the secondary coil by electromagnetic induction in the direction, which prevents a reduction of the magnetic fi eld in the primary coil. The GREEN LED is on due to the current created by the EMF and we are reading microamps on the DMM. 15. Why does the DMM register microamps when the inner (primary) coil is moved in and out of the outer (secondary) coil? 16. Fill in the blanks: When the polarity switch is moved to the RIGHT, the LED turns on, and the compass needle points to the pole. 17. What principle explains why the secondary coil gets voltage when the magnetic fi eld in the primary coil changes? A. Magnetic saturation B. Static electricity C. Mutual induction D. Thermal conduction Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 60 95-CL-1902 Module C — SA-12 LEVEL 3 SA-12 LEVEL 3 Magnetic Field Collapse E ect Objective : Students will analyze how the collapse of a magnetic fi eld in the secondary coil causes a surge in current fl ow to explain its role in ignition system performance. Material Required : DMM and Compass. 1. Connect the Red lead from the Blue power supply receptacle to the blue receptacle of Module C inner (primary) coil. 2. Connect the Black lead from the Yellow receptacle of the power supply to the Yellow receptacle of the C inner (primary) coil. 3. Place the compass to the right of the C outer (secondary) coil. 4. Connect a red lead from the Galvanometer Blue receptacle to the C outer (secondary) coil Blue receptacle. 5. Connect a black lead from the Galvanometer Yellow receptacle to the C outer (secondary) coil Yellow receptacle. 6. Hook-up a DMM to the Module C outer (secondary) coil. 7. Connect the DMM red lead from the μA port to the outer (second- ary) coil Blue receptacle 8. Connect the DMM black lead from common ground to the outer (secondary) coil Yellow receptacle. 9. Place the compass to the right of outer (secondary) coil. 10. Set the DMM to read μA on the 4,000 μA scale with Min-Max Record Max set. 11. Turn on the Power supply. 12. Flip the polarity switch to the left, RED diode will light and the com- pass needle will point south showing the presence of a magnetic fi eld. 13. Move the primary coil in & out of the secondary and DMM will reg- ister microamps. This exercise measured ± 508 μA. 14. The Galvanometer will show current increase and the DMM will show anywhere from 800 to 2200 microamps. consulab.com info@consulab.com 61 95-CL-1902 Module C — SA-12 LEVEL 3 15. Pull the C primary coil out of the C secondary coil. The compass needle moves away from the South pole, showing the magnetic fi eld has collapsed. 16. Disconnect primary coil ground. 17. Push the C Primary Coil Back and Forth in and out of the Secondary Coil, then quickly reconnect the Primary coil ground and the DMM will register higher amperage than in Step 13. 18. Explain the relationship between magnetic fi eld collapse and induced current in the secondary coil. Why does the DMM reading increase when the primary coil ground is reconnected quickly? 19. Predict what would happen if the secondary coil had fewer turns or if the iron core was removed. How would this a ect the induced current and why ? consulab.com info@consulab.com 62 95-CL-1902 Module C — SA-12 LEVEL 3 — Answer Sheet Name : Group : Date : Instructor : Grade : 20. True or False: The timing of magnetic fi eld collapse is critical for proper ignition system operation. Explain your answer. CONCLUSION This assignment demonstrates how the collapse of the C secondary coil magnetic fi eld causes an increase in secndary current as demonstrated on the Galvanometer and the DMM as in an ignition coil. Review information on Mutual Induction in the theory section if necessary. consulab.com 63 95-CL-1902 Module B-1, B-2 and C Student Assessment Module B-1, B-2 and C Student Assessment Before taking this test, be sure to have your completed Module assignments available. Use the answer sheet for your answers. 1. Technician A says that self-inductance is the induction of an EMF (Electromotive Force) in a circuit when the current in that circuit is varied. Technician B says that Lenz’s Law states that this self-induced voltage tends to increase the current that produces it. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 2. Using the above formula for self-induction, if the time remains constant and the number of lines of force also remain constant measured by a change in current. Which of these is the result ? A. No CEMF (Counterelectromotive force) created in the coil. B. CEMF (Counterelectromotive force) created in the coil. C. As current decreases, the magnetic fl ux lines created by the current increases. D. Magnetic fl ux created by the current is di erent from the EMF (Electromotive force). 3. Which of these is generated by electromagnetic induction in the coil, which prevents the magnetic fl ux created by the current from decreasing and the direction of the current ? A. Magnetic Flux B. EMF (Electromotive Force) C. CEMF (Counterelectromotive Force) D. Reluctance 4. In SA-7 Level 1 assignment on Self-Inductance, when you place the compass on top of the B2 Coil and turn on the power switch, which of these takes place ? A. Compass needle points North. B. Compass needle points South. C. Compass needle does not move. D. Compass needle points east . CL-1902 ELECTROMAG TRAINER 54 Self-Inductance Figure 16 Self-Inductance Self-inductance is the induction of an EMF in a circuit when the current in that circuit is varied not constant. It resists or opposes the change of current flowing through it. This occurs due to the self-induced EMF produced in the coil. Self-inductance is the induction of a voltage in a current-carrying wire. Lenz's Law states that this self-induced voltage tends to oppose the current that produces it. If the current continues to increase, the second voltage opposes the increase. When the current stabilizes, the counter voltage is no longer induced because there are no more expanding flux lines (no relative motion). When current to the coil is shut off, the collapsing magnetic flux lines self-induce a voltage in the coil that tries to maintain the original current. The self-induced voltage opposes and slows down the decrease in the original current. The self-induced voltage that opposes the source voltage is called Counterelectromotive force (CEMF) or a Back EMF. Just for reference, the equation for Self-Inductance is shown below 𝐸𝐸 = −𝐿𝐿 ΔI Δt • E = The EMF generated • -L = Self-Inductance measured in Henrys • I = change in current in coil • t = change in elapsed time Using the above formula as reference, current change from an Alternator or battery (Figure 16) between let’s say the time difference (t) remains constant the number of lines of force measured by a change in current (I) also remain constant. The result is no CEMF created in the coil during this time period. If the current is removed the battery current decreases between t1 and t2. As this current decreases, the magnetic flux lines created by the current also decreases. A CEMF is generated by electromagnetic induction in the coil, which prevents the magnetic flux created by the current from decreasing and the direction of the current due to this CEMF is the same as the EMF generated by the AC generator or battery current. The Back-EMF opposed any change in the current in a circuit. The self-inductance acts as inertia. So, work needs to be done against the Back-EMF in establishing the current. This work done is stored as magnetic potential energy to pull in the armature in an Automotive Solenoid. E = The EMF generated −L = Self-Inductance measured in Henrys I = Change in current in coil t = Change in elapsed time 5. In SA-8 Level 2 assignment on Mutual Inductance when you turn on the Power Switch, the GREEN LED will turn on indicating power fl ow and which of these takes place ? A. Steel rod moves to the right. B. Steel rod moves to the left. C. Compass needle points West. D. Compass needle points North. consulab.com info@consulab.com 64 95-CL-1902 Module B-1, B-2 and C Student Assessment 6. In Step #11 of SA-8 Level 2 assignment on Mutual Inductance, when you turn o the power switch and move the compass from the B2 Coil to the B1 Coil, the compass rotates to the North Pole indicating which of these ? A. Presence of a CEMF (Counterelectromotive Force) B. Presence of an EMF (Electromotive Force) C. Presence of high current D. Presence of low current 7. Two technicians are discussing step 6 of SA-9 Level 3 assignment on Mutual Inductance. Technician A says the direction of the B1 coil EMF (Electromotive Force) is the same as that of the B2 Coil. Technician 2 says that the EMF causes the Galvanometer to show an increase in current. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 8. What lesson can be learned from In SA-7 Level 1 assignment on Self-Inductance ? Technician A says that the EMF is called a CEMF (Counter Electromotive Force) or Back-EMF. Technician B says that a magnetic fi eld created by the induced current opposes changes in the initial magnetic fi eld. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 9. Technician A says that the magnetic property of a coil which a ects or changes the voltage in another coil is called self-Induction. Technician B says that the primary winding of a coil changes electrical energy from the battery into magnetic energy of the expanding fi eld. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 10. The ignition coil creates a high-voltage spark using which of these : A. Electromagnetic induction B. Action Reaction C. Ohm’s Law D. Watt’s Law 11. In SA-10 Level 1 assignment on Center Core Action, you turn the polarity toggle switch to the left or right. Technician A says the core pieces move up and down. Technician B says that there is no change in core piece movement. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B consulab.com info@consulab.com 65 95-CL-1902 Module B-1, B-2 and C Student Assessment 12. If you were using a DMM (Digital Multimeter) to measure the current resulting from Mutual Induction exercise, what settings would you be using ? A. Red Lead VΩ and mA/A position B. Black lead COM and mA/A position C. Min-Max Record, 400 µA scale D. Min-Max Record, 4,000 µA scale 13. Two technicians are discussing SA-11 Level 2 assignment on Mutual Induction. TTechnician A says that in Step 2, the moment you move the polarity switch to the LEFT the RED LED (Light Emitting Diode), turns on and compass RED needle will point to the North. Technician B says that in Step 2 you place the compass to the right of the C Module outer or Secondary Coil and turn on the power supply. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 14. In step 2 of SA-11 Level 2 assignment on Mutual Induction, With the polarity switch in the LEFT position for Positive to Negative fl ow, the current fl owing through inner or Primary Coil decreases and will become : A. 0 volt B. 5 volts C. 12 millivolts D. 24 millivolts 15. The magnetic property of a coil which a ects or changes the voltage in another coil is called which of these : A. Self-Induction B. Mutual Induction C. Primary Induction D. Secondary Induction 16. Two Technicians are describing the principle of mutual induction. Technician A says that when two coils are close together and connected through a common iron core, energy may be transferred from one to the other through a magnetic coupling. Technician B says that mutual induction means that the expansion or collapse of the magnetic fi eld around one coil induces a voltage in the second coil. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B consulab.com info@consulab.com 66 95-CL-1902 Module B-1, B-2 and C Student Assessment 17. In the above illustration as part of SA-12 Level 3 assignment on Mutual Induction, what action has taken place ? A. Collapse of the magnetic fi eld in the inner (primary) coil B. Creation of the magnetic fi eld in the inner (primary) coil C. Collapse of the magnetic fi eld in the outer (secondary) coil D. Creation of the magnetic fi eld in the outer (secondary) coil 18. Technician A says that SA-12 Level 3 assignment demonstrates how the collapse of the C Secondary or outer coil magnetic fi eld causes an decrease in secondary current as demonstrated on the Galvanometer. Technician B says that the Galvanometer will show current increase in that same assignment. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 19. When the magnetic fi eld has expanded to its full strength, it remains steady as long as the same amount of : A. Current exists. B. Voltage exists. C. Wattage exists. D. Resistance exists. 20. The principle of Mutual Inductance has been demonstrated in SA-12 Level 3 assignment. Which of these automotive components is used ? A. AC Generator B. Ignition coil C. Battery D. Starter Motor Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 67 95-CL-1902 Module D — SA-13 LEVEL 1 Module D — Right Hand Rule SA-13 LEVEL 1 Applying Lenz’s Law Objective : Students will apply the Right-Hand Rule to determine the direction of induced current according to Lenz’s Law. Material Required : Compass. 1. Connect the Red lead from the power supply Blue receptacle to the Blue receptacle on Module D. 2. Connect the Black lead from the power supply Yellow receptacle to the Yellow receptacle on Module D. 3. Turn on the power supply on the 12 volt side and Flip the polarity switch to the left for a Positive to Negative current fl ow. 4. Place your right hand as shown to simulate the right hand rule with your thumb in the positive to negative current fl ow and your fi nder will point in the direction of the magnetic fi eld. 5. Place the compass between the control unit and Module D. The compass is pointing to the North Pole showing the presence of the magnetic lines of force or fl ux. 6. Fill in the Blank: The thumb in the Right Hand Rule represents the direction of fl ow. 7. True or False. The compass needle moves because of the magnetic fi eld created by the current. 8. Name one automotive component that uses the principle demonstrated in this activity. CONCLUSION In the conventional theory of current positive to negative or ground (+ to −), the right-hand rule is used to determine the direction of the magnetic fl ux lines as shown under step 4 by the compass point north and changes when removed. The rule says if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direction of current fl ow (positive to negative), your curved fi ngers would point in the direction of the lines of force. DD consulab.com info@consulab.com 68 95-CL-1902 Module D — SA-14 LEVEL 2 SA-14 LEVEL 2 Magnetic Field Orientation Objective : Use the Right-Hand Rule to see how magnetic fi eld direction changes with polarity. Material Required : Compass. 1. Connect the Red lead from the power supply Blue receptacle to the Blue receptacle on Module D. 2. Connect the Black lead from the power supply Yellow receptacle to the Yellow receptacle on Module D. 3. Turn on the power supply on the 12 volt circuit and place the polar- ity switch to the left for positive to negative current fl ow. 4. Place the compass on the Red lead wire and note the direction of the arrow. The compass needle points South. 5. Place the compass on the Black lead wire and note the direction of the arrow. The compass arrow moves to the left showing the di erence in the magnetic lines of force from the positive lead to the negative lead. 6. When the compass is placed on the Red lead, which direction does the needle point, and what does this indicate about the magnetic fi eld? A. It points North, showing no magnetic fi eld. B. It points South, showing the magnetic fi eld direction. C. It does not move, showing no current fl ow. DD Current Flow Magnetic Field + - consulab.com info@consulab.com 69 95-CL-1902 Module D — SA-14 LEVEL 2 7. Draw both wires (Red lead and Black lead). For each wire: *Show the direction of current fl ow with an arrow along the wire. **Use curved arrows around the wire to show the direction of the magnetic fi eld (fl ux lines). 8. If the polarity switch were toggled repeatedly, what e ect would this have on the magnetic fi elds around the leads? Explain why this happens. CONCLUSION This assignment demonstrates the magnetic fl ux line of force change from the negative side to the positive side. The direction of the electric current which is induced in a conductor by a changing magnetic fi eld is such that the magnetic fi eld created by the induced current opposes changes in the initial magnetic fi eld. This is Lentz’s Law. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 70 95-CL-1902 Module D — SA-15 LEVEL 3 SA-15 LEVEL 3 Determining Flux Direction Objective : Apply the Right-Hand Rule to fi nd the direction of magnetic fl ux lines. Material Required : None. 1. Connect the Red lead from the power supply Blue receptacle to the Blue receptacle on Module D. 2. Connect the Black lead from the power supply Yellow receptacle to the Yellow receptacle on Module D. 3. You can also connect the Galvanometer into the circuit to view the current changes. Connect a Red lead from the Blue Galvanometer receptacle on top of the power Blue receptacle of Module D. 4. Connect a Black lead from the Yellow Galvanometer receptacle on top of the Black lead of the Yellow receptacle of Module D. 5. Turn on the Power switch on the 12 volt circuit. 6. Toggle the polarity switch back and forth from Positive to Nega- tive to Negative to Positive current fl ow. This may not work at fi rst due to inertia (An Object stays at rest unless moved by an outside force). You will have to nudge it a bit, then the wagon wheel will move back and forth as the polarity switch is moved. 7. This picture shows the location on the copper rails of the D module, where the wagon wheel should start to move back and forth. DD DD GG consulab.com info@consulab.com 71 95-CL-1902 Module D — SA-15 LEVEL 3 8. This picture shows the most left side position of the wagon wheel when in the Positive to Negative position. 9. When the wagon wheel is moved back and forth, in the Positive to Negative position, the Galvanometer needle will swing all the way to the left showing a large gain in microampere current. 10. This picture shows the most right side position of the wagon wheel when in the This is the most left side position of the wagon wheel when in Negative to Positive position. 11. When the wagon wheel is moved back and forth, in the Negative to Positive position, the Galvanometer needle will swing all the way to the right showing a large gain in microampere current. consulab.com info@consulab.com 72 95-CL-1902 Module D — SA-15 LEVEL 3 12. How does reversing polarity in the circuit cause the wagon wheel to move? 13. Fill in the Blank. In this assignment, energy was converted into energy. 14. If the polarity switch stayed in one position and was never toggled, what would happen to the wagon wheel and why? CONCLUSION This exercise demonstrates how the Right Hand Rule is used to determine the direction of the magnetic fl ux lines. It states that if you wrapped your right hand around a current-carrying conductor with your thumb pointing in the direc- tion of current fl ow (positive to negative), your curved fi ngers would point in the direction of the lines of force. It further demonstrates how an increase in current takes place and how the opposing poles cause the wagon wheel to move back and forth in the same way an electric motor or solenoid would opperate. Review information on Right Hand Rule in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 73 95-CL-1902 Module D Student Assessment Module D Student Assessment Before taking this test, be sure to have your completed Module assignments available. Use the answer sheet for your answers. 1. The magnetic lines of force around a conductor, like the copper rails in Module D, form circular patterns. Which rule can you use to determine the direction of these lines of force based on the current fl ow? A. Coulomb’s Law B. Ohm’s Law C. Left Hand Rule D. Right Hand Rule 2. Two technicians are explaining the Right Hand Rule. Technician A says that the magnetic fi eld around a conductor may be strong enough to perform useful work as in moving the wagon wheel. Technician B says that in order to concentrate the magnetic fi eld, the wire can be looped into a coil. The fewer loops, the stronger the magnetic fi eld. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 3. Why does the compass needle move when placed near a current-carrying conductor? A. Heat from the wire a ects the compass B. Magnetic fi eld created by the current interacts with the compass C. Voltage changes cause the compass to spin D. The compass detects electric charge 4. The right hand rule says if you wrapped your right hand around a current-carrying conductor, your curved fi ngers would point : A. In the direction of the current fl ow B. Left to right C. In the direction of the lines of force D. Right to left 5. Which law explains why the magnetic fi eld changes when polarity is reversed? A. Ohm’s Law B. Lenz’s Law C. Faraday’s Law D. Coulomb’s Law consulab.com info@consulab.com 74 95-CL-1902 Module D Student Assessment 6. The magnetic lines of force around a conductor are A. Straight lines along the wire B. Circular patterns around the wire C. Zigzag patterns D. Random directions 7. Why does the wagon wheel move when you fl ip the polarity switch back and forth? A. Gravity acting on the wheel B. Extra voltage from the power supply C. Opposing magnetic fi elds created by reversing current direction D. Heat from the wires 8. In the wagon wheel experiment, electrical energy is converted into: A. Heat energy B. Light Energy C. Chemical energy D. Mechanical energy 9. When an object is at rest, it tends to stay at rest unless acted on by an outside force. What might you need to do to overcome inertia and start the wagon wheel moving? A. Nudge the wheel B. Reverse the Red and Black leads C. Toggle the voltage from 10 to 12 volts D. Toggle the polarity switch. 10. Technician A says opposing magnetic fi elds can create motion in a motor. Technician B says opposing magnetic fi elds only cancel each other out and cannot produce motion. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A nor B Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 75 95-CL-1902 Module E — SA-16 LEVEL 1 Module E — AC Generation SA-16 LEVEL 1 Rotor Current Action Objective : Observe how rotor movement generates AC in a generator. Material Required : DMM and DSO (optional). 1. Connect the Red lead from the Galvanometer Blue receptacle to the Blue receptacle on Module E top row. 2. Connect the Black lead from the Galvanometer supply Yellow re- ceptacle to the Yellow receptacle on Module E. 3. Connect a DMM (Digital Multimeter) into the Generator circuit by placing a Red Lead from the µA receptacle of the DMM to the top of the Red lead from the Galvanometer. 4. Connect a Black Lead from the DMM Ground receptacle on top of the Galvanometer Black Lead. 5. Set the DMM on the 4,000 µA scale with the Min-Max Record on Max se to DC. 6. With the rubber O-Ring belt on the pulley, crank the Generator as fast as you can and not the results. The DMM registered ± 1,424 µA. 7. The Galvanometer showed current output. 8. A correlation between : 9. The waveform produced by an AC generator is typically a wave. GG EE A-1A-1 USING AN OSCILLOSCOPE WITH THE CL-1902 ELECTRO-MAG TRAINER The CL-1902 Electro-Mag trainer does not absolutely require the use of an oscilloscope to complete any of the student assignment or to use the trainer as a demonstrational teaching aids. The power supply’s built-in voltmeter, ammeter and micro-ammeter (Galvanometer) will provide accuracy and visual confirmation of component operation. In addition, the compass and magnetic field indicator provides additional visual aids for student understanding. An oscilloscope is a visual display voltage device that displays voltage over a given period of time. A digital multimeter converts a voltage measurement into a digital numeric display using numbers for a given value. An oscilloscope displays voltages as traceable lines on a screen that changes with time. Both the voltage and time settings can be adjusted for specific viewing needs. Oscilloscopes can easily display extremely low voltages and over very fast time periods. Digital multimeters have limitations on what voltages they can accurately measure and often struggle measuring with very fast voltage signals. The CL-1902 Electro-Mag trainer includes components that generate very low voltages. The oscilloscope is very well suited to view these signals which can provide additional clarity for student understanding and comprehension of what is going on. The following images are provided for your reference and demonstration of how an oscilloscope was used to capture the voltage signals generated or modified by the modules that are on the trainer. The oscilloscope used for the captures was the uScope which represents a very affordable yet, powerful diagnostic tool that is very popular in the vehicle repair industry. However, any oscilloscope can be used including Snapon, OTC, Pico, Hantek, Autel, Ditech and many other brands. The included waveform captures and the associated voltage and time adjustment settings used will provide additional understanding for those instructors choosing to utilize this powerful diagnostic tool with the trainer. There are countless other experiments and exercises that can be performed with this trainer in addition to those included in the curriculum. OSCILLOSCOPE WAVEFORMS FROM CL-1902 ELECTRO-MAG TRAINER MODULES A-1 & A-2 Module A-1 with hand mov- ing 3” magnet rod back and forth inside coil — No trainer power turned on faster speed increases amplitude and frequency consulab.com info@consulab.com 76 95-CL-1902 Module E — SA-16 LEVEL 1 10. Which instrument can display the actual AC waveform? A. Digital Multimeter (DMM) B. Galvanometer C. Digital Storage Oscilloscope (DSO) D. Ammeter 11. The symbol μA represents which unit of measurement? A. Microamps B. Milliamps C. Uniamps D. Nanoamps CONCLUSION The action of the rotor current in the AC Generator cause a current output in the Generator Stator, which measured 1,424 µA on the GM and showed a current increase on the Galvanometer. If a DSO (Digital Storage Oscilloscope) when connected to the circuit, with would see a full Sine Waveform as is shown above. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 77 95-CL-1902 Module E — SA-17 LEVEL 2 SA-17 LEVEL 2 Half-Wave Rectifi cation Objective : Observe how rotor movement generates AC in a generator. Material Required : DMM and DSO (optional). 1. Connect the Red lead from the Yellow receptacle of Module E stator output to the Yellow receptacle of the single Diode. 2. Connect a Black lead from the Blue receptacle of the other Module E stator output. 3. Connect a Black lead from the Galvanometer Yellow receptacle to the top of the Black lead from the E module. 4. Connect a Red lead from the Galvanometer Blue receptacle to the top of the Red lead from the E module. 5. Connect a DMM Red Lead from the µA receptacle of the DMM to the top of the Red lead from the Galvanometer. 6. Connect a Black Lead from the DMM Ground receptacle to the top of the Galvanometer Black Lead. 7. Set the DMM on the 4,000 µA scale with the Min-Max Record on Max set on DC. 8. With the rubber O-Ring belt on the pulleys, crank the Generator as fast as you can and not the results : the DMM registered ± 1,764 µA. An Oscilloscope would show a half wave pattern because the current is DC and only going in one direction. This would be ½ the Sine Waveform that would have been generated in Step 6 of SA-16 Level 1 on Current Generation. 9. The galvanometer measures in the circuit and indicates the direction of fl ow. 10. A diode allows current to fl ow in direction only, which helps convert current to direct current, because . EE EE GG MODULES A-1 & A-2 (CONTINUED) MODULES A-1 & A-2 (CONTINUED) Module A-1 with hand moving 3” magnet rod back and forth inside coil — one end of coil connected to diode on Module E with other end diode con- nected to scope — reverse polarity as shown. No trainer power turned on — shows half wave rectifi cation negative polarity. consulab.com info@consulab.com 78 95-CL-1902 Module E — SA-17 LEVEL 2 11. What is the primary function of the diode in this setup? A. To increase the voltage B. To rectify AC into DC C. To measure current fl ow D. To store electrical energy 12. Why does the oscilloscope display a half-wave pattern in this experiment? A. The generator produces DC naturally B. The DMM is set to DC mode C. The galvanometer limits the waveform D. The diode blocks half of the AC cycle CONCLUSION In the Half-Wave single-phase voltage shown in this exercise, we had current fl ow through a simple circuit, the current would fl ow fi rst in one direction and then in the opposite direction. As long as the rotor turned, the current would re- verse its fl ow with every half revolution and generating alternating current. Alternating current must be rectifi ed to direct current to recharge the battery. This is done with diodes. A DSO pattern would show a half-wave pattern to the left. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 79 95-CL-1902 Module E — SA-18 LEVEL 3 SA-18 LEVEL 3 Full-Wave Rectifi cation Objective : Demonstrate full-wave rectifi cation. Material Required : DMM. 1. Take a Black lead and connect it from the Yellow Receptacle of Module E to the Black receptacle of the Diode Rectifi er bridge. 2. Connect a Red lead from the Blue receptacle of Module E to the Red receptacle of the Diode Rectifi er bridge. 3. Connect a Black Lead from the Diode Rectifi er Bridge Blue Recepta- cle to the Diode Rectifi er Bridge Red receptacle. 4. Connect a Red lead from the Diode Bridge Rectifi er Black recepta- cle to the Diode Bridge Rectifi er Yellow receptacle. 5. Connect the Galvanometer and DMM into the circuit. 6. Connect the Black Leads from the meters piggyback to the Diode Bridge Rectifi er Black Receptacle. 7. Connect the Red Leads from the meters piggyback to the Diode Bridge Rectifi er Red Receptacle. 8. Set the DMM on the 400 mA scale with the Min-Max Record on Max set on DC. NOTE: 1 amp (A) = 1,000 milliamps (mA). So 400 mA = 0.4 A 9. Crank the E module crank to generate current out of the Diode Bridge Rectifi er. The Galvanometer will show a larger microampere current than the Half-Wave Rectifi er but not captured. The DMM captures the amperage at ± 37.2 milliamps EE GG EE consulab.com info@consulab.com 80 95-CL-1902 Module E — SA-18 LEVEL 3 10. You can also capture the current in µA : ± 1,688 microamperes. 11. You can also measure the current in AC using the same DMM set- tings, just toggle it for AC using the Blue button. You can see up to ± 200.8 milliamps AC. 12. You can also measure the DC voltage out of the Diode Rectifi er Bridge, setting the DMM for DC Volts. It registered ± 0.164 VDC. 13. Fill in the Blank: A Half-Wave Rectifi er uses diode(s) and al- lows half of the AC cycle to pass, while a Full- Wave Rectifi er uses diodes and converts halves of the AC cycle into DC. 14. What happens if one diode in the bridge fails? A. The circuit will still work perfectly B. The current will become stronger C. The rectifi er will act like a half-wave rectifi er D. The battery will charge faster 15. What car part uses full-wave rectifi cation, and why is it important? 16. What is the main di erence between a half-wave rectifi er and a full-wave rectifi er? CONCLUSION The diode bridge rectifi er in Module E is an bridge arrangement of 4 diodes connected in a loop. As AC voltage is induced in loop, it is converted to DC voltage by the diodes in the bridge. The diodes convert all the AC voltage to DC voltage. Due to the fact that all of the AC voltage is converted into DC voltage, this diode bridge rectifi er is referred to as a full-wave rectifi er. A full wave rectifi er converts both halves of each cycle of an alternating wave (AC signal) into a pulsating DC signal. Full-wave rectifi ers convert AC voltage to DC voltage using multiple diodes. Full wave rectifi cation is the process of converting an AC signal to a DC signal. Adding more diodes to the circuit allows more AC voltage to be rectifi ed to DC. This is why the current we measured in this exercise was greater than the current generated in the Half- Wave Rectifi er. Review information on AC Generator Charging System in the theory section if necessary. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 81 95-CL-1902 Module E Student Assessment Module E Student Assessment Before taking this test, be sure to have your completed Module assignments available. Use the answer sheet for your answers. 1. What type of waveform does an AC generator produce? A. Square B. Sine C. Half-wave D. Digital 2. Which statement best describes the action of the rotor in an AC generator? A. It creates a steady DC current. B. It causes the current to alternate direction as it spins. C. It blocks current fl ow during half the cycle. D. It converts AC to DC. 3. Alternating Current (AC) is rectifi ed to DC (Direct Current) using : A. Diode Bridge Rectifi er B. Transistor Bridge Rectifi er C. Capacitor D. Thermistor Bridge 4. The Wire loop in a generator is connected to a split ring called a : A. Regulator B. Carbon Brush Set C. Armature D. Commutator 5. What device is shown in this illustration ? A. Rotor B. Stator C. Commutator D. Armature CL-1902 ELECTROMAG TRAINER 106 5. What device is shown in the above illustration? A. Rotor B. Stator C. Commutator D. Armature ANSWER____________ 6. In the above illustration what is used for a Half-Wave Rectifier? A. Single Diode B. Multiple Diodes C. Transistor D. Capacitor ANSWER____________ 7. In Step 2 of EE1L1 D1. Exercise 1: LEVEL 1 Current Generation, what is used to power the E Module? A. Battery B. Power Supply C. F2 Module D. Crank and Pulley ANSWER____________ consulab.com info@consulab.com 82 95-CL-1902 Module E Student Assessment 6. In the next illustration what is used for a Half-Wave Rectifi er ? A. Single Diode B. Multiple Diodes C. Transistor D. Capacitor 7. What is the source of power for the E Module in a basic generator setup? A. Battery B. Power Supply C. Module F-2 D. Crank and Pulley 8. In an alternator, the Brush-Type Alternator uses carbon brushes that ride on : A. Slip rings B. Rotating bearings C. Commutator D. Wire loop conductor 9. Two technicians explain how current fl ows in an AC generator. Technician A says the current fl ows fi rst in one direction and then the opposite. Technician B says the current reverses every full turn of the rotor. Who is correct? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 10. Which of these in an alternator is a conductor replacing the wire-loop commutator of the DC generator ? A. Rotor B. Stator C. Commutator D. Rectifi er 11. Which of these in an alternator is the magnetic fi eld generator replacing the fi eld coils or permanent magnets of the DC generator ? A. Rotor B. Stator C. Commutator D. Rectifi er consulab.com info@consulab.com 83 95-CL-1902 Module E Student Assessment 12. What does full-wave rectifi cation do? A. Converts only one half of the AC cycle into DC B. Converts both halves of the AC cycle into DC C. Changes DC into AC for battery charging D. Blocks all current fl ow during the negative cycle 13. Why do we connect the galvanometer and DMM in parallel to the diode bridge? A. To measure voltage only B. To measure current fl ow without breaking the circuit C. To block AC from entering the meters D. To increase the circuit resistance 14. Which of these shows the greatest amount of current? A. 1,500 μA B. 15 mA C. 0.015 A D. 1,800 μA 15. In thist illustration, Technician A says when the magnetic lines of force crosses or cuts a conductor (Wire Loop) it induces a voltage in that conductor. Technician B says that the DC generator uses an iron core or laminated iron sheets to create an electromagnet. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 16. What is taking place in the next illustration to an alternator ? A. Resistance in series added to the fi eld circuit B. Current in series added to the fi eld circuit C. Resistance in parallel added to the fi eld circuit D. Current in parallel added to the fi eld circuit 17. Which rectifi er produces more average current, and why? A. Half-wave rectifi er, because it uses only one diode B. Half-wave rectifi er, because it uses both halves of AC C. Full-wave rectifi er, because it uses both halves of AC D. Full-wave rectifi er, because it blocks both halves of AC 18. How does full-wave rectifi cation di er from half-wave rectifi cation? A. Full-wave uses one diode, half-wave uses four diodes B. Full-wave converts only one half of the AC cycle, half-wave converts both halves C. Full-wave converts both halves of the AC cycle, half-wave converts only one half D. Full-wave blocks all current during the negative cycle, half-wave allows both halves LAMINATED CORE FIELDLINE OF FORCE WIRE LOOP CARBON BRUSH SPLIT RING COMMUTATOR N S AC Voltage Regulator Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 84 95-CL-1902 Module F-1 and module F-2 — SA-19 LEVEL 1 Module F-1 and module F-2 SA-19 LEVEL 1 F-1 Motor Operation (3 pages) Use the answer sheet for your answers. Do not write on this page. Objective : Demosntrate that the motor speed can be controlled with the brush position when operating a motor. Material Required : None. 1. Connect a Red lead from the Power Supply Blue receptacle to the Blue receptacle of Module F-1. 2. Connect a Black lead from the Power Supply Yellow receptacle to the Yellow receptacle of Module F-1. 3. Connect a Red Lead from the Bipolar Diode Blue receptacle to the F-1 Motor Blue receptacle. 4. Connect a Black Lead from the Bipolar Diode Yellow receptacle to the F-1 Motor Yellow receptacle. 5. Piggyback the Galvanometer in the positions as the Bipolar Diode. 6. Crank the F-1 Motor in the counterclockwise direction and the Bipolar Diode will be Green and the Galvanometer with be showing current fl ow to the left. 7. Crank the F-1 Motor in the clockwise direction and the Bipolar Diode will be RED and the Galvanometer with be showing current fl ow to the right. F-1F-1 F-1F-1 GGBDBD consulab.com info@consulab.com 85 95-CL-1902 Module F-1 and module F-2 — SA-19 LEVEL 1 8. Disconnect the rubber O-Ring belt to the crank pulley and make sure that the F-1 and F-2 motors are not connected. 9. The F-1 motor is a variable speed motor with a set of movable brushes and only a 2 segment commutator with just 2 magnetic fi eld coils. Moving the brush set to an advanced position allows the motor speed to increase. The speed of a motor can be varied in 3 ways : • Varying supply voltage • Varying fl ux, and varying current through the fi eld winding • Varying armature voltage, and varying armature resistance 10. Turn on the Power Supply in 12 volts and turn the Polarity Switch to the left for positive to negative power fl ow. 11. You will need to turn the motor armature on the left a small amount to get the motor to run or it may run with the brush set moved all the way toward the Power Supply. 12. Once running, move the brush set all the way toward the Power Supply to get the maximum motor speed. F-1F-1 F-2F-2 consulab.com info@consulab.com 86 95-CL-1902 Module F-1 and module F-2 — SA-19 LEVEL 1 13. Turn o the power supply. Take the motor belt and place it around the hand crank. Pull the belt as shown in the photo, with the motor at the maximum speed, place the belt on the motor shaft armature and the motor will stop. NOTE : Make sure that none of your wire leads get tangled in the motor shafts. 14. Remove the drive belt from the motor armature and the motor will spin again 15. Move the brush set toward the motor receptacles to get the mini- mum motor speed and the motor will stop. 16. Fill in the blank : Reversing the of the supply leads changes the motor’s direction of rotation. Increasing the applied will generally increase the motor’s speed and current draw. The F-1 motor converts energy into energy. CONCLUSION When you connect power to the F-1 Module Motor it will operate with a slight nudge to the armanture or with the brushes pushed toward the Power Supply in the maxium advance position. If you move the brush set back and forth the motor speed with vary. This demosntrates that the motor speed can be controlled with the brush position. This was done by varying the armature voltage, and the armature resistance. Variable speed motors are found in automotive applications. Some are called Stepper Motors because they move in steps. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 87 95-CL-1902 Module F-1 and module F-2 — SA-20 LEVEL 2 SA-20 LEVEL 2 Motor Design and Direction Objective : Demonstrate that a motor with more fi eld coils and more segments on the commutator will turn faster and its direction can be reverse by changing the polarity. Material Required : None. 1. Connect a Red lead from the Power Supply Blue receptacle to the Blue receptacle of Module F-2. 2. Connect a Black lead from the Power Supply Yellow receptacle to the Yellow receptacle of Module F-2. NOTE : Make sure that none of your wire leads get tangled in the motor shafts. 3. Do not connect the rubber O-Ring belt to the crank pulley and make sure that the F-1 and F-2 motors are not connected. NOTE : Make sure that none of your wire leads get tangled in the motor shafts. 4. Turn on the Power Supply in 12 volts and turn the Polarity Switch to the left for positive to negative current fl ow. You will notice that this motor has more fi eld coils than the F-1 Motor and spins much faster. F-2F-2 F-1F-1 F-2F-2 consulab.com info@consulab.com 88 95-CL-1902 Module F-1 and module F-2 — SA-20 LEVEL 2 5. Flip the Polarity Switch to the right for negative to positive current fl ow. The F-2 Motor will now turn in the opposite direction at the same speed. You can fl ip it multiple times to see the reverse rota- tion. 6. Which feature of the F-2 motor shows it is an induction motor rath- er than a permanent magnet (PM) motor? A. It relies on induced current in the rotor instead of fi xed magnets B. It uses a commutator and brushes C. It cannot reverse direction when polarity changes D. It produces DC output when driven mechanically 7. How does increasing voltage a ect speed and current in the F-2 motor compared to the F-1 motor? 8. Does reversing polarity still change the F-2 motor’s direction like in SA-19? Explain briefl y. CONCLUSION A motor with more fi eld coils and more segments on the commutator will turn faster and its direction can be reverse by changing the polarity. This type of setup would work well for an automtive power window. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 89 95-CL-1902 Module F-1 and module F-2 — SA-21 LEVEL 3 SA-21 LEVEL 3 Motoras a Generator Objective : Demonstrate that a DC motor can be turned into a generator. Material Required : DMM. 1. Connect a Red lead from the Power Supply Blue receptacle to the Blue receptacle of Module F-2. 2. Connect a Black lead from the Power Supply Yellow receptacle to the Yellow receptacle of Module F-2. NOTE : Make sure that none of your wire leads get tangled in the motor shafts. 3. Move the coupler in between the F-1 and F-2 modules to connect the two motors together. 4. Connect a Red lead from Blue Receptacle of Galvanometer to the Blue receptacle of the F-1 Motor. 5. Connect a Black lead from the Yellow Receptacle of the Galvanom- eter to the Yellow receptacle of the F-1 Motor. 6. Connect DMM into the circuit by placing a Red Lead from the mA receptacle of the DMM to the top of the Red lead from the Galva- nometer. 7. Connect a Black Lead from the DMM Ground receptacle on top of the Galvanometer Black Lead. 8. Set the DMM on the 400 mA scale for AC. Set the Min-Max Record for MAX. F-2F-2 GG F-1F-1 consulab.com info@consulab.com 90 95-CL-1902 Module F-1 and module F-2 — SA-21 LEVEL 3 9. Install the belt and turn the hand crank as fast as you can and record the amperage and note the Galvanometer. 10. A current of 74.5 milliamps AC was measured and the Galvanome- ter went almost all the way to the left. 11. Set the DMM for AC Volts using autorange by moving the DMM Red lead from the mA / µA receptacle to the Volt Ohm receptacle. 12. Crank the motor and record the millivolts shown as ± 316 millivolts. 13. Remove Drive belt O-Ring o the F-2 Motor. F-2F-2 consulab.com info@consulab.com 91 95-CL-1902 Module F-1 and module F-2 — SA-21 LEVEL 3 14. Reset the DMM for Milliamps. 15. Connect DMM into the circuit by placing a Red Lead from the mA receptacle of the DMM to the top of the Red lead from the Galva- nometer. 16. Connect a Black Lead from the DMM Ground receptacle on top of the Galvanometer Black Lead. 17. Set the DMM on the 400 mA scale for AC. 18. Set the Min-Max Record for MAX. 19. Turn on the power supply and place the polarity switch to the Left for Positive to Negative current fl ow. 20. Record the milliamps current generated at ± 97.6 mA. 21. The motor will speed up and the current went to ± 102.4 mA. 22. Turn the polarity switch to the right for negative to positive current fl ow and record the amperage in reverse. DMM shows ± 92.2 mA. AC Voltage in mV in reverse was ± 0.527 mV AC. 23. Note the reading on the Galvanometer swing to the right. consulab.com info@consulab.com 92 95-CL-1902 Module F-1 and module F-2 — SA-21 LEVEL 3 24. Set the DMM for AC Volts using autorange by moving the DMM Red lead from the mA/µA receptacle to the Volt Ohm receptacle . 25. Turn on the power supply with the polarity switch to the left for positive to negative current fl ow and record the millivolts shown as ± 316 millivolts, which is the same voltage found during the crank test until the motor speed increased. 26. As the motor speed increased so did the voltage output up to ± 401.6 mV. 27. Which factor most directly a ects the voltage output of a DC motor acting as a generator? A. Motor Speed B. Wire Color C. Galvanometer sensitivity D. Belt tension 28. When the polarity switch is reversed during the experiment, what happens to the galvanometer needle? A. It stays centered B. It swings to the left C. It swings to the right D. It oscillates rapidly 29. Why does the generated current increase when the motor speed increases? A. Higher speed reduces resistance B. The belt creates additional torque C. The DMM changes its range automatically D. Faster rotation induces a stronger EMF 30. During the crank test, the voltage measured was ±316 mV. When powered, it increased to ±401.6 mV. What caused this increase? CONCLUSION A DC motor can be turned into a generator because it operates under the same magnetic rules as the DC generator. The speed of a DC motor incresed due to inertia and the voltage and amperage increased with the speed. Speed was the only changeable parameter to increase motor speed. The faster the motor turned the more the voltage and amper- age output increased. Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 93 95-CL-1902 Module F-1 and F-2 Students Assessments Module F-1 and F-2 Students Assessments Before taking this test, be sure to have your completed Module assignments available. 1. Electric Motors work on principle of : A. Magnetic Repulsion B. Inertia C. Negative Energy D. Magnetic Propulsion 2. This question contains the word EXCEPT. Read the question carefully before choosing your answer. All of these can vary the speed of a motor, EXCEPT : A. Varying supply voltage. B. Varying fl ux, and varying current through the fi eld winding. C. Varying armature voltage, and varying armature resistance. D. Varying the fl ux capacitance. 3. Two technicians are explaining electric motor operation. Technician A says that current fl ows from negative (−) battery terminal through the brush and copper ring nearer the S-Pole, through the armature to the copper ring and brush nearer the N-Pole and back to the Positive (+) battery terminal. Technician B says that electrical fl ow causes the portion of the loop near the N-Pole to push downward and the S-Pole to push upward. When there is a strong fi eld on one side of the conductor and a weak fi eld on the other side, the conductor will move from the strong to the weak. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 4. In an electric motor, the armature rotates due to which of these between N and S-Poles on one side of the conduc- tor ? A. Weaker magnetic fi eld B. Stronger magnetic fi eld C. Stronger current fl ow D. Weaker current fl ow 5. When connecting a DC motor to a power supply, where should the positive (red) lead from the power supply be connected? A. To the blue receptacle of the motor B. To the yellow receptacle of the motor C. To the negative terminal of the motor D. To the ground terminal 6. What device is used in the circuit to detect the direction of current fl ow? A. Digital Multimeter B. Voltmeter C. Bipolar diode D. Ammeter consulab.com info@consulab.com 94 95-CL-1902 Module F-1 and F-2 Students Assessments 7. Which statement best describes the di erence between the F-1 and F-2 motors? A. F-1 has more fi eld coils and higher speed than F-2 B. F-2 has more fi eld coils and can produce higher torque than F-1 C. F-1 is designed for generator operation only D. F-2 cannot reverse polarity 8. Technician A says that the F-1 motor is a variable speed motor with a set of movable brushes and only a 2 segment commutator with just 4 magnetic fi eld coils. Technician B says that moving the brush set toward the power supply cause the motor peed to increase. Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 9. With the F-1 module motor at the maximum speed, when you connect the drive belt to the motor armature, what happens ? A. Motor speed doubles B. Motor Speed increases C. Motor Stops D. Motor stops and starts 10. Two technicians are discussing motor safety and setup. Technician A says that a drive belt should only be installed- when the motor is powered and running. Technician B says that motors should never be mechanically linked togeth- er during single-motor tests. Based on these statements, who is correct: A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 11. When the polarity switch on a DC motor circuit is fl ipped, what happens to the direction of current fl ow? A. It changes from negative to positive B. It changes from positive to negative C. It reverses direction D. It stays the same 12. Why does the F-2 motor turn faster than the F-1 motor when both use the same voltage? A. It has more fi eld coils B. It has fewer fi eld coils C. It has less resistance D. It draws more current 13. A motor with more fi eld coils and more segments on the commutator will turn faster and its direction can be reverse by : A. Reducing the fi eld count. B. Increasing the voltage. C. Reducing the number of commutator segments. D. Changing the polarity. consulab.com info@consulab.com 95 95-CL-1902 Module F-1 and F-2 Students Assessments 14. Two technicians are discussing electric motor operation. Technician A says that the magnetic lines of force stretch and tries to shorten itself. Technician B says that there is a strong magnetic fi eld on both sides of the looped con- ductor (armature-commutator-brushes). Who is right ? A. Technician A only B. Technician B only C. Both Technician A and Technician B D. Neither Technician A nor Technician B 15. What is the main function of a commutator in a DC motor? A. To increase voltage B. To reverse current direction in the armature C. To reduce resistance D. To store electrical energy 16. Which component of a DC motor creates the magnetic fi eld? A. Armature B. Brushes C. Field windings D. Commutator 17. Why are brushes used in a DC motor? A. To cool the motor B. To increase magnetic fl ux C. To provide electrical contact between stationary and rotating parts D. To measure voltage 18. What is the di erence between an electric motor and an electric generator? A. A motor converts electrical energy to mechanical energy; a generator converts mechanical energy to electrical energy B. A motor uses AC; a generator uses DC C. A motor produces voltage; a generator produces torque D. A motor cannot reverse polarity; a generator can 19. Which factor does NOT a ect the speed of a DC motor? A. Color of the motor housing B. Armature resistance C. Magnetic fl ux D. Supply Voltage 20. In the CL-1902 assignments for the F-2 motor to drive the F-1 AC generator, what parameter was used to increase amperage ? A. Voltage B. Amperage C. Speed D. Resistance Name : Group : Date : Instructor : Grade : consulab.com info@consulab.com 96 95-CL-1902 Glossary Glossary Alternator An AC generator in a vehicle that converts mechanical energy into electrical energy to charge the battery and power systems. Armature The rotating part of an electric motor or generator that carries current and interacts with the magnetic fi eld. Back EMF Voltage induced in a coil or motor that opposes the applied voltage, reducing current fl ow as speed increas- es. Brushes Carbon contacts that transfer current to or from the rotating commutator in a motor or generator. Coil Polarity The magnetic polarity (North or South) created at the ends of a coil when current fl ows through it. Coil Windings Turns of wire wrapped around a core to create a magnetic fi eld when energized. Commutator A split copper ring on a motor armature that reverses current direction to maintain rotation. Conductor A material that allows electricity to fl ow easily, like copper wire. Conventional Flow Theory Assumes current fl ows from positive to negative, even though electrons go the opposite way. Converter A device that changes one DC voltage level to another (e.g., 12V to 5V). Current The fl ow of electric charge through a conductor. Diode A component that allows current to fl ow in only one direction. Diode Bridge Rectifi er A circuit of four diodes arranged in a bridge to convert AC to DC. Diodes Plural of diode; often refers to multiple diodes used in rectifi ers. Electromagnet A magnet created by running current through a coil of wire. Electromagnetic Induction The process of generating voltage by moving a conductor through a magnetic fi eld. Electromotive Force (EMF) Voltage that pushes current through a circuit. Electrical Energy Energy from moving electrons in a circuit. Faraday’s First Law States that a changing magnetic fi eld induces an EMF in a conductor. Faraday’s Second Law States that the induced EMF is proportional to the rate of change of magnetic fl ux. Field Winding Coils that produce a magnetic fi eld in motors or generators when energized. Flux Density How concentrated magnetic fl ux is in a given area. Flux Lines Lines that represent the path of magnetic fl ux between poles. These are often used interchangeably with Lines of Force, which show the direction of magnetic fi eld strength from the North pole to the South pole. Full-Wave Diode Rectifi er Bridge A rectifi er using four diodes to convert both halves of an AC waveform into DC. Gauss Gauge A tool for measuring magnetic fi eld strength. Generator A device that turns mechanical energy into electrical energy. consulab.com info@consulab.com 97 95-CL-1902 Glossary Half-Wave Rectifi er A rectifi er that uses one diode to allow only half of the AC cycle to pass. Inertia The tendency of an object to resist changes in motion. Inverter A device that converts DC into AC, often used to power AC motors in hybrid vehicles. Kinetic Energy Energy of motion, like moving electrons or rotating parts. Lenz’s Law States that induced current opposes the change that caused it. Lines of Force Imaginary lines showing the direction of a magnetic fi eld, from North to South pole. These are equivalent to Flux Lines, and both terms are used to illustrate magnetic fi eld patterns. Magnetic Coupling The interaction between two magnetic fi elds, often in transformers or inductors. Magnetic Field The area around a magnet or current-carrying wire where magnetic forces act. Magnetic Flux The amount of magnetic fi eld passing through an area. Magnetic Induction The process of creating voltage in a conductor by changing magnetic fl ux. Magnetic Repulsion The force that pushes two like magnetic poles apart. Magnitude The size or amount of something, without direction. Mechanical Energy Energy from motion or position, like moving parts in a machine Mutual Induction When a changing current in one coil induces voltage in another coil. Permanent Magnet A magnet that stays magnetized without electricity. Polarity The property of having two poles, North and South, in a magnet or circuit. Potential Energy Stored energy due to position or condition, such as a charged battery. Rectifi er A device that converts AC to DC using diodes. Resistance The opposition to current fl ow in a circuit, measured in ohms (Ω). Higher resistance reduces current. Right Hand Rule A way to fi nd magnetic fi eld direction: thumb points current, fi ngers show fi eld. Self-Inductance The property of a coil to oppose changes in its own current by inducing voltage. Sine Wave A smooth, repetitive oscillation representing AC voltage or current. Slip Rings Circular contacts that transfer current to a rotating part without reversing polarity. Solenoid A coil of wire that creates a magnetic fi eld when current fl ows through it. Solenoid Actuator An electromagnetic device that moves a plunger in a straight line for rapid on/o motion. Vector Quantity A value with both size and direction, like force or magnetic fi eld. Voltage The electrical potential di erence that pushes current through a circuit, measured in volts (V). Voltage is also called Electromotive Force (EMF) because it provides the “force” that drives electrons through a conductor. Voltage Regulator A device that controls voltage output by adjusting fi eld current in an alternator. Work Energy transferred when a force moves something over a distance. consulab.com info@consulab.com 98 95-CL-1902 Notes Notes 400-6330 Zéphirin-Paquet St. Québec QC G2C 0M3 Canada © ConsuLab Educatech Inc, 2025. All rights reserved.
