# A straight copper wire is held between the poles of a horseshoe magnet. The wire is connected to a sensitive voltmeter. Explain what happens to the voltmeter reading when the wire is moved quickly upwards, then held still, and then moved slowly downwards.

> WJEC A-Level Physics (Wales) — 4.5 Electromagnetic induction · Explain · 5 marks

## Mark scheme (5 marks)

1. When the wire moves upwards, an e.m.f. / voltage is induced in the wire
2. Moving quickly produces a larger induced e.m.f. than moving slowly (faster movement = greater e.m.f.)
3. When the wire is held still, there is no induced e.m.f. and the voltmeter reads zero
4. When the wire moves downwards, the induced e.m.f. is in the opposite direction
5. Moving slowly downwards produces a smaller induced e.m.f. than moving quickly upwards (lower speed = smaller e.m.f.)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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