3-20
Figure 3-17.—Solenoid action.
While a solenoid is a control device, the solenoid itself is energized by some other control device
such as a switch or a relay. One of the distinct advantages in the use of solenoids is that a mechanical
movement can be accomplished at a considerable distance from the control device. The only link
necessary between the control device and the solenoid is the electrical wiring for the coil current. The
solenoid can have large contacts for the control of high current. Therefore, the solenoid also provides a
means of controlling high current with a low current switch. For example, the ignition switch on an
automobile controls the large current of a starter motor by the use of a solenoid. Figure 3-18 shows a
cutaway view of a starter motor-solenoid combination and a section of the wiring for the solenoid. Notice
that the solenoid provides all electrical contact for current to the starter motor as well as a mechanical
movement of the shift lever.
