OBJECTIVES. After studying Chapter 13, the reader should be able to: Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic Systems). Explain magnetism. Describe how magnetism and voltage are related.
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After studying Chapter 13, the reader should be able to:
FIGURE 13-1 A freely suspended natural magnet will point toward
the magnetic north pole.
FIGURE 13-2 If a magnet breaks or is cracked, it becomes two weaker magnets.
FIGURE 13-3 Magnetic lines of force leave the north pole and return to the south pole of a bar magnet.
FIGURE 13-4 Iron filings on a compass can be used to observe the magnetic lines of force.
FIGURE 13-5 Magnetic poles behave like electrically charged
particles—unlike poles attract and like poles repel.
FIGURE 13-6 A magnetic field surrounds a straight current-carrying conductor.
FIGURE 13-7 The left-hand rule for magnetic field direction is used with the electron flow theory.
FIGURE 13-8 The right-hand rule for magnetic field direction is used with the conventional theory of electron flow.
FIGURE 13-9 Conductors with opposing magnetic fields will move apart into weaker fields.
FIGURE 13-10 Electric motors use the interaction of magnetic fields to produce mechanical energy.
FIGURE 13-11 The magnetic lines of flux surrounding a coil look similar to those surrounding
a bar magnet.
FIGURE 13-12 The left-hand rule for coils is shown.
FIGURE 13-13 An iron core concentrates the magnetic lines of force surrounding a coil.
FIGURE 13-14 An electromagnetic relay.
FIGURE 13-15 In this electromagnetic switch, a light current (low amperes) produces an electromagnet and causes the contact points to close. The contact points then conduct a heavy current (high amperes) to an electrical
FIGURE 13-16 Voltage can be induced by the relative motion
between a conductor and magnetic lines of force.
FIGURE 13-17 No voltage is induced if the conductor is moved in the same direction as the magnetic lines of force (flux lines).
FIGURE 13-18 Maximum voltage is induced when conductors cut across the magnetic lines of force (flux lines) at a 90 degree angle.
FIGURE 13-19 Mutual induction occurs when the expansion or collapse of a magnetic field around one coil induces a voltage in a second coil.
FIGURE 13-20 Internal construction of an oil-cooled ignition coil. Notice that the primary winding is electrically connected to the secondary winding. The polarity (positive or negative) of a coil is determined by the direction in which the coil is wound.
FIGURE 13-21 Typical air-cooled epoxy-filled E coil.
FIGURE 13-22 Cutaway of a General Motors Type II distributorless
ignition coil. Note that the primary windings are inside of the secondary
FIGURE 13-23 A tapped (married) type of ignition coil where the primary winding is tapped (connected) to the secondary winding.
FIGURE 13-24 To help prevent under-hood electromagnetic devices
from interfering with the antenna input, it is important that the hood be
grounded to the body to form one continuous metal covering around the engine compartment. This is particularly important if the vehicle has a front fender-mounted antenna. This braided ground strap is standard equipment on this Dodge Caliber and helps eliminate radio interference.
4. Electricity creates magnetism and magnetism creates electricity.
5. Radio-frequency interference (RFI) is a part of electromagnetic interference (EMI).
2. Unlike magnetic poles _____ and like magnetic poles _____.
3. The conventional theory for current flow is being used to determine the direction of magnetic lines of force. Technician A says that the left-hand rule should be used. Technician B says that the right-hand rule should be used. Which technician is correct?
4. Technician A says that a relay is an electromagnetic switch. Technician B says that a solenoid uses a movable core. Which technician is correct?
5. Two technicians are discussing electromagnetic induction. Technician A says that the induced voltage can be increased if the speed is increased between the conductor and the magnetic lines of force. Technician B says that the induced voltage can be increased by increasing the strength of the magnetic field. Which technician is correct?
6. An ignition coil operates using the principle of _____.
7. Electromagnetic interference can be reduced by using a _____.
8. An ignition coil is an example of a _____.
9. Magnetic field strength is measured in _____.
10. Two technicians are discussing ignition coils. Technician A says that some ignition coils have the primary and secondary windings electrically connected. Technician B says that some coils have totally separate primary and secondary windings that are not electrically connected. Which technician is correct?