What is the role of a commutator in generators?

• A. To cool the windings
• B. To measure output frequency
• C. To mechanically rectify/convert AC to DC in the armature
• D. To regulate voltage by adjusting resistance

Answer: (C)

The essential idea is that the commutator turns the alternating voltage generated in the armature into direct current for the load by switching the connections as the rotor turns. In a DC generator, the armature windings are spinning in a magnetic field and produce AC in the coils. The commutator is a split ring connected to the ends of those coils; as the coil passes through the neutral plane, the commutator reverses which end is connected to the external circuit via the brushes. This keeps the current delivered to the load flowing in one direction, effectively rectifying the AC mechanically from the armature. The resulting pulsating DC is what the aircraft electrical system uses, often smoothed by filters and regulated by the voltage regulator, not by changing resistance in the circuit.

This function isn’t about cooling windings, measuring output frequency, or regulating voltage by resistance—those are handled by cooling systems, frequency measurement equipment, and electrical regulators that control field current, respectively.