Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

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58 Chapter Four
Figure 4-13.
weak field.
Conductors will move together into the
Figure 4-15.
Loop conductor. (Delphi Corporation)
Figure 4-14. Electric motors use field interaction to
produce mechanical energy and movement.
interacts with the magnetic fields of the poles.
The clockwise field of the top conductor adds to
the fields of the poles and creates a strong field
beneath the conductor. The conductor tries to
move up to get out of this strong field. The
counterclockwise field of the lower conductor
adds to the field of the poles and creates a strong
field above the conductor. The conductor tries
to move down to get out of this strong field.
These forces cause the center of the motor or
armature where the conductors are mounted to
turn in a clockwise direction. This process is
known as magnetic repulsion. For more information
about electric motors, see the section on
“Diagnostic Strategies” in Chapter 4 of the
Shop Manual.
Loop Conductor
Bending the wire into a loop can strengthen the
field around a straight conductor. As the wire is
bent, the fields, which meet in the center of the
Figure 4-16.
Coil conductor.
loop, combine their strengths (Figure 4-15). The
left-hand rule also applies to loop conductors.
Coil Conductor
If several loops of wire are made into a coil, the
magnetic flux density is further strengthened.
Flux lines around a coil are the same as the flux
lines around a bar magnet (Figure 4-16). They
exit from the north pole and enter at the south
pole. Use the left-hand rule to determine the north
pole of a coil. If you grasp a coil with your left
hand so that your fingers point in the direction of
electron flow, your thumb points toward the north
pole of the coil, Figure 4-17. Increasing the number
of turns in the wire, or increasing the current
through the coil, or both, can strengthen the magnetic
field of a coil.