How does a motor work?

Question 1

Describe what happens in a d.c motor.

Answer 1

1. A current-carrying wire sits between two poles in a uniform m.f.
2. According to Flem. LHR, the current flowing in different directions on each side of the coil causes each side to experience a force that acts perpendicular to the m.f produced by the magnets in opposite directions.
3. This causes the coil to rotate.
4. The split-ring commutator swaps the contacts every half-turn to keep the motor rotating in the same direction - it reverses the direction of the current every half turn.

Question 2

Describe what happens in an alternator.

Answer 2

1. A magnet rotates in a fixed coil of wire.
2. The direction of the field that the coil passes through alternates.
3. This produces an alternating current.

Question 3

What’s different about an alternator in comparison to a d.c motor?

Answer 3

An alternator uses a slip-ring commutator, but a d.c motor uses a split-ring commutator.