What is the primary purpose of brushes on a DC motor?

The primary purpose of brushes on a DC motor is to allow current flow reversal in the armature. In a DC motor, the armature (the rotating part of the motor) requires a direct current to generate rotational motion. The brushes are in contact with the commutator, which is connected to the armature winding. As the armature rotates, the commutator segments switch the connections to the power source, ensuring that the current flowing through the armature winding changes direction appropriately. This switching action is crucial for maintaining the rotational direction of the motor, allowing it to operate smoothly and effectively.

The function of the brushes is essential for the motor's operation as they maintain a continuous electrical connection between the stationary parts of the motor and the rotating armature, enabling the magnetic field to interact with the armature's winding and produce motion. This is fundamental to the performance of the motor, distinguishing DC motors from other types.

Other choices, while relevant in different contexts, do not capture the primary function of brushes within the mechanism of a DC motor. The increase in efficiency, noise reduction, and rotor support are not direct roles fulfilled by brushes in the operation of a DC motor.