# A student notices that the plastic insulation on a mains cable has been damaged, exposing the live wire. Explain why this damaged insulation is dangerous and describe how a fuse protects the user if a short circuit occurs as a result.

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

> A household electric kettle is plugged into the mains supply. The mains supply in the UK is an alternating current supply at 230 V and 50 Hz. The cable connecting the kettle to the wall socket has a section of damaged insulation where the plastic covering has cracked and split, leaving the live wire exposed.

## Mark scheme (4 marks)

1. Damaged insulation means a person who touches the exposed live wire can receive an electric shock / current can flow through the person to earth
2. Damaged insulation / exposed live wire touching another conductor can create a short circuit, causing a large/surge of current to flow
3. The large current causes the thin metal wire/filament inside the fuse to overheat and melt/blow
4. When the fuse melts it breaks/cuts off the circuit, disconnecting the appliance from the mains supply and protecting the user

## Key terms

- [damaged insulation](https://www.gradenine.co.uk/glossary/damaged-insulation)
- [live wire](https://www.gradenine.co.uk/glossary/live-wire)
- [short circuit](https://www.gradenine.co.uk/glossary/short-circuit)
- [fuse](https://www.gradenine.co.uk/glossary/fuse)

## 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-student-notices-that-the-plastic-5e7d4858) · Published by Druglandscape Ltd.