ICSE Class 10 Answered

Carbon brushes are used to make contact of a stationary wire with rotating rotor in DC motor.

For getting torque in the same direction throughout the rotation, it is necessary to reverse the direction of current

flowing through the rotor winding in every half cycle.

This is called “commutation” and it is achieved by supplying the rotor current through brushes.

The brushes are fixed to stator and they connect to copper plates fixed to rotor.

As the rotator rotates, the brushes supply current in the right direction.

The brushes are made of carbon because carbon is a reasonably good conductor of electricity

and it is soft, so it makes good contact. However the brushes wear out and have to be replaced periodically.