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Question 17

(a) What is the purpose of the brushes in a DC motor?

Answer:
The brushes provide a sliding contact between the commutator on the motor’s armature and the power supply.

(b) Why is graphite commonly used for these brushes?

Answer:
Graphite, as well as being conductive, is a lubricant. It keeps the motor’s commutator slippery so it does not slow down when in contact with the brushes.

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