HSC Physics Practice Exam

The rotating part in an electric motor or generator is known as the rotor. The rotor is crucial because it is responsible for interacting with the magnetic field to produce rotational motion in motors or to generate electrical current in generators.

In electric motors, when electric current flows through the rotor, it creates a magnetic field that interacts with the magnetic field of the stator (the stationary part of the motor), causing the rotor to turn. In generators, the rotor spins within a magnetic field, inducing an electric current in the coils of wire attached to it.

The stator, on the other hand, does not move; it provides a magnetic field and is essential for the operation of the rotor. The commutator is a device found in some types of electric motors, particularly in DC motors, used to maintain the direction of current and ensure a continuous rotation. Slip rings are used in AC generators and some types of motors to transfer current from the rotor to the external circuitry without interrupting the rotation.

Thus, the rotor is the primary component that rotates in both electric motors and generators, making it the correct answer to identify the rotating part.