Practice Questions

1.What does an alternator do?

An alternator is a generator that produces an alternating current (ac).

2. How is the construction of an alternator different to that of a motor?

A motor contains a split ring commutator, which swaps the contacts every half turn. 

An alternator has slip rings which allow a permanent electrical connection with free rotation, but it does not swap the contacts every half turn.

3. Describe how a graph of potential difference vs time would change as the coil rotates 360 degrees

Starting when the coil is horizontal the magnetic field lines are cut by the coil, so a maximum induced potential difference is induced.

When the coil is rotated 90 degrees clockwise, the coil is vertical, not cutting the field lines so the potential difference is zero

If the coil is flipped by 180 degrees from starting horizontal position it is cutting the field lines, but the induced potential difference changes direction.

A further rotation of 90 degrees will make the coil  vertical again, the magnetic field lines are not cut, so the potential difference is zero.