# A technician is testing a bicycle dynamo. When the cyclist pedals faster, the dynamo produces a larger potential difference. Explain why increasing the speed of the rotating magnet inside the dynamo causes a larger potential difference to be induced in the coil.

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

> A bicycle dynamo contains a magnet that spins inside a coil of wire. The spinning magnet induces a potential difference in the coil, which lights the bicycle's lamp.

## Mark scheme (4 marks)

1. A changing/moving magnetic field induces a potential difference in the coil
2. Increasing speed means the magnetic field through the coil changes more rapidly / the rate of change of the magnetic field increases
3. A greater rate of change of the magnetic field induces a greater / larger potential difference
4. This is because the induced potential difference depends on / is proportional to the rate of change of the magnetic field (or rate at which field lines are cut)

## Key terms

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

## 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/a-technician-is-testing-a-bicycle-90707eae) · Published by Druglandscape Ltd.