Page 280 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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264 Automobile mechanical and electrical systems

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Figure 3.13 Induction

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Figure 3.14 Transformer: as the switch is turned on and off the voltmeter needle will move

shape of magnetic fi elds in diagrams. Electromagnets are used in motors, relays
and fuel injectors, to name just a few. Force on a current carrying conductor in

Key fact a magnetic fi eld results from two magnetic fi elds interacting. This is the basic
Magnetism can be created by principle of how a motor works.
a permanent magnet or by an When a conductor cuts or is cut by magnetism a voltage is induced in the
electromagnet.
conductor ( Fig. 3.13 ). The direction of this voltage depends on the direction of the
magnetic fi eld and the direction in which the fi eld moves relative to the conductor.
The size is proportional to the rate at which the conductor cuts or is cut by the
magnetism. This effect of induction, meaning that voltage is made in the wire, is
the basic principle of how generators such as the alternator in a car work.
A generator is a machine that converts mechanical energy into electrical energy.
If two coils, primary and secondary, are wound on to the same iron core, any
change in magnetism of one coil will induce a voltage in the other. This happens
when the primary current is switched on and off ( Fig. 3.14 ). If the number of turns
of wire on the secondary coil is more than on the primary, a higher voltage can be
produced. This is called transformer action and is the principle of the ignition coil.

3.1.2 Electrical components and circuits

A switch is a simple device used to break a circuit; that is, it prevents the fl ow
of current. A wide range of switches is used. Some switches are simple on/off
devices such as an interior light switch on the door pillar. Other types of switch
are more complex. They can contain several sets of contacts to control, for