What is the necessity of copper brushes in a dc motors?

Electrical Engineering MCQ Electrical Machines MCQ
1

What is the necessity of copper brushes in a dc motors?

A. To absorb the mechanical shocks produced during running condition.
B. To convert alternating supply current to direct current.
C. To increase the flux cutting by the rotor.
D. None of these.

Show Answer

Answer: D

Share your understanding of this question with the correct explanation.

2

The necessity of copper brushes in DC motors is not related to any of the options provided.

Copper brushes are used in DC motors for their electrical conductivity and low friction properties. When the rotor of a DC motor rotates, the copper brushes make sliding contact with the commutator segments, which are connected to the armature windings. The main functions of the copper brushes are:

  1. Electrical Conduction: The brushes provide a low-resistance electrical connection between the power supply and the rotating armature. They allow the current to flow from the power source into the rotating armature, enabling the generation of the electromagnetic field and the production of torque.
  2. Low Friction: The brushes need to have a low friction coefficient to minimize wear and reduce the generation of heat and sparks at the contact interface with the commutator. Copper brushes offer good electrical conductivity and suitable friction properties for this purpose.

Therefore, the correct answer is D. None of these options accurately describes the necessity of copper brushes in a DC motor.