# A lawnmower has a metal casing and is connected to the mains electricity supply using a three-core cable. The three-core cable contains a live wire, a neutral wire and an earth wire. Explain the role of the fuse and the earth wire in keeping a user safe if the live wire inside the lawnmower accidentally touches the metal casing.

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

## Mark scheme (4 marks)

1. The live wire touching the metal casing causes a large/surge of current to flow through the earth wire (because the earth wire has a very low resistance).
2. The earth wire provides a safe/low resistance path for the current to flow to earth, preventing the metal casing from becoming live.
3. The large current through the fuse causes the fuse wire to overheat and melt/blow.
4. The fuse breaking the circuit disconnects/cuts off the power supply to the lawnmower, preventing electric shock or fire.

## 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)

## 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-lawnmower-has-a-metal-casing-23b193e2) · Published by Druglandscape Ltd.