Question

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because

• A. Current is drawn from a stationary source
• B. Current is drawn from a moving source
• C. Direct current is produced
• D. It is not necessary to reverse the direction of the current.

Answer 1

The correct option is D It is not necessary to reverse the direction of the current.

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because It is not necessary to reverse the direction of the current.The brushes transfer the electricity from outside the motor to the spinning winding in the center of the motor. They undergo quite a lot of friction, and after a while wear out. Carbon is used as it is a reasonable conductor, and is soft enough to wear down instead of wearing down the "comutator" - the ring the brushes press against. Brushes are designed to be replaceable in large motors because of this.