# A student uses a hairdryer at home. The hairdryer is connected to the mains supply using a three-pin plug fitted with a fuse and an earth wire. Explain how the earth wire and fuse together protect the user if the live wire inside the hairdryer accidentally touches the metal casing.

> Cambridge International IGCSE Physics (0625) — 4.4 Electrical safety · Explain · 4 marks

## Mark scheme (4 marks)

1. The earth wire connects the metal casing to earth (at 0 V / ground potential)
2. A large/surge current flows through the earth wire (because the resistance of the earth wire is very low)
3. The large current melts/breaks the fuse wire (fuse 'blows')
4. The circuit is broken / disconnected so no current can flow, protecting the user from electric shock

## Key terms

- [earth wire](https://www.gradenine.co.uk/glossary/earth-wire)
- [fuse](https://www.gradenine.co.uk/glossary/fuse)
- [live wire](https://www.gradenine.co.uk/glossary/live-wire)
- [metal casing](https://www.gradenine.co.uk/glossary/metal-casing)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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-student-uses-a-hairdryer-at-34b548a3) · Published by Druglandscape Ltd.