# A bicycle dynamo contains a coil of wire that rotates inside a magnetic field. As the cyclist pedals faster, the dynamo produces a larger voltage. Explain why a voltage is produced in the coil and why pedalling faster increases the size of this voltage.

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

## Mark scheme (5 marks)

1. The rotating coil cuts through magnetic field lines (or the magnetic field through the coil changes)
2. This induces a voltage (e.m.f.) in the coil
3. Pedalling faster increases the speed of rotation of the coil
4. The coil cuts field lines more frequently / the rate of change of the magnetic field through the coil increases
5. A greater rate of change of the magnetic field induces a larger voltage

## Key terms

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

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-bicycle-dynamo-contains-a-coil-69873965) · Published by Druglandscape Ltd.