In motor control, which device is used to switch power to the motor and is energized by the control circuit?

• A. Switch
• B. Fuse
• C. Contactor
• D. Relay

Answer: (C)

In motor control, the device that is energized by the control circuit to switch power to the motor is the contactor. A contactor has a control coil that receives a signal from the control circuit; when energized, it pulls in its main contacts and closes the circuit to deliver power to the motor. This setup lets a low-power control signal accurately control a high-current motor circuit, and contactors are built to handle the large currents and frequent on/off cycling motors require.

A manual switch could physically start or stop a motor, but it isn’t driven by the control circuit automatically. A fuse provides protection by interrupting current if a fault occurs, rather than being used to actively switch power in response to control signals. A relay is similar in concept but is typically used for lower currents; for motor power, a contactor is the appropriate, robust choice designed for high-current switching.