What is one of the major parts of a DC motor?

A commutator is a critical component of a DC motor as it plays a key role in the operation of the motor by reversing the direction of current flow through the windings as the motor turns. This reversal is essential for maintaining the rotational motion of the motor; without it, the motor would come to a stop once it reached a certain position, as the magnetic fields would no longer interact in a productive way. The commutator is essentially a rotary switch that connects the motor's armature windings to the direct current source, ensuring that the windings are energized at the right time to produce continuous rotation.

In contrast, other components mentioned, such as inductors, rectifiers, and diodes, serve different functions in electrical systems and are not intrinsic to the basic operation of a DC motor. An inductor stores energy in a magnetic field, while a rectifier converts alternating current (AC) to direct current (DC), and a diode allows current to flow in one direction only. While these components may be used in conjunction with DC motors in broader electrical systems, they do not contribute to the core functionality of the motor itself.