# A transformer is used in the electricity distribution system to change the voltage of an alternating current supply. Explain why a transformer cannot work with a direct current supply.

> Eduqas GCSE Physics — 8.3 Induced potential and transformers · Explain · 4 marks

## Mark scheme (4 marks)

1. A direct current produces a magnetic field that does not change (is constant/steady)
2. A changing magnetic field is required to induce a voltage (in the secondary coil)
3. Alternating current continuously changes direction, so the magnetic field in the core continuously changes
4. This changing magnetic field induces a voltage in the secondary coil, so a transformer only works with alternating current

## Key terms

- [transformer](https://www.gradenine.co.uk/glossary/transformer)
- [alternating current](https://www.gradenine.co.uk/glossary/alternating-current)
- [direct current](https://www.gradenine.co.uk/glossary/direct-current)

## Related

- [Revision notes for Eduqas GCSE Physics](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-transformer-is-used-in-the-6ebedb2c) · Published by Druglandscape Ltd.