# A step-down transformer is used to reduce the potential difference from the National Grid before electricity is supplied to homes. Describe how a step-down transformer works, including why the number of turns on each coil is important.

> AQA GCSE Physics (8463) — 4.7.3 Induced potential, transformers and the National Grid (Phys only) · Describe · 4 marks

## Mark scheme (4 marks)

1. Alternating current in the primary coil creates a changing magnetic field (in the iron core)
2. The changing magnetic field induces a potential difference in the secondary coil
3. The secondary coil has fewer turns than the primary coil
4. Fewer turns on the secondary coil means a lower potential difference is produced / the output potential difference is smaller than the input

## Key terms

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

## Related

- [Revision notes for AQA GCSE Physics (8463)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-step-down-transformer-is-used-to-036c60f0) · Published by Druglandscape Ltd.