4
practice testMultiple Choice

Practice Test

Question 4 • Physical Science

Which best compares a brush and a commutator in an electric motor?

Answer
A
Both rotate when the motor is on.
B
Both remain stationary when the motor is on.
C
Both carry electrical current from a power source.
D
Both have a permanent magnetic field.

Explanation

A brush makes electrical contact with the rotating commutator, allowing current from the power source to reach the motor’s rotating coil. The brush stays stationary, while the commutator rotates, but both carry electrical current. So the best comparison is that both carry current from a power source.

AI-written and checked against the verified answer.

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