# Explain why a potential difference is induced across the ends of a straight wire when the wire is moved through a magnetic field, and describe two ways the magnitude of the induced potential difference could be increased.

> OCR GCSE Physics A: Gateway Science (J249) — P3.4 Electromagnetic induction · Explain · 4 marks

> An engineer is testing a simple generator by moving a length of straight copper wire between the poles of a horseshoe magnet. A voltmeter connected to the ends of the wire shows a reading whenever the wire moves.

## Mark scheme (4 marks)

1. The wire cuts through magnetic field lines (as it moves), causing an induced potential difference
2. Electrons in the wire experience a force, causing them to move / build up at one end, creating a potential difference
3. Increase the speed at which the wire moves through the field
4. Use a stronger magnet (to increase the magnetic field strength)

## Key terms

- [induced potential difference](https://www.gradenine.co.uk/glossary/induced-potential-difference)
- [magnetic field](https://www.gradenine.co.uk/glossary/magnetic-field)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-a-potential-difference-is-5fd37863) · Published by Druglandscape Ltd.