# A electric drill has a metal casing and is connected to the mains electricity supply using a three-core cable. The drill is switched on and begins to overheat, causing a large surge in current. Explain how the earth wire and fuse together protect the user from electric shock.

> Pearson Edexcel International GCSE Physics (4PH1) — 2.1 Mains electricity · Explain · 4 marks

## Mark scheme (4 marks)

1. The earth wire connects the metal casing to earth, providing a low resistance path for current to flow
2. This prevents the metal casing from becoming live / prevents the user receiving an electric shock
3. The large surge of current through the earth wire causes the fuse to overheat and melt / blow
4. The circuit is broken / the power supply to the drill is cut off, making the appliance safe

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](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-electric-drill-has-a-metal-69c0ba59) · Published by Druglandscape Ltd.