Which of the following lists the four main parts of a DC motor?

• A. Armature, rotor, stator, windings
• B. Field frame, windings, yoke, rotor
• C. Armature, field coil, commutator, bearings
• D. Armature, field frame, commutator, brushes

Answer: (D)

The key idea is identifying the four main functional components that allow a DC motor to produce torque and control current: a rotating armature, a stationary field assembly, the device that switches current to the rotating windings, and the electrical contacts that feed that switching device.

In a DC motor, the armature is the rotating windings where torque is developed. The field frame holds the stationary magnetic field—this is the field assembly that provides the flux needed for motor action. The commutator is the rotating switch that reverses current in the armature windings as it turns, keeping the torque in one direction. The brushes are the stationary contacts that maintain current flow to the commutator as the motor spins.

Other options mix incompatible parts or omit essential ones—like swapping rotor for armature without addressing the commutation pair, or replacing the field frame with unrelated parts such as bearings or yokes. The combination armature, field frame, commutator, and brushes correctly represents the four main parts of a DC motor.