Which device converts electrical energy into mechanical energy via a rotating magnetic field?

• A. Capacitor
• B. Relay
• C. Motor
• D. Inductor

Answer: (C)

The device that converts electrical energy into mechanical energy through a rotating magnetic field is the motor. When a motor is powered, the stator windings generate magnetic poles that rotate, creating a rotating magnetic field. The rotor responds to this moving field, producing torque and turning, which is the mechanical energy output. In three-phase motors, the stator currents are phase-shifted to create a smooth, continuous rotating field that drives the rotor efficiently.

Capacitors store energy in an electric field, inductors store energy in a magnetic field and resist changes in current, and relays act as switches driven by electromagnets. None of these produce continuous mechanical rotation by a rotating magnetic field, so they don’t perform the same energy conversion.