# A student connects a length of nichrome wire to a battery. The student then replaces the nichrome wire with a piece of rubber of the same dimensions. Explain why the nichrome wire conducts electricity but the rubber does not.

> WJEC A-Level Physics (Wales) — 2.1 Conduction and resistance · Explain · 5 marks

> Nichrome is a metal alloy. Rubber is a non-metallic insulator.

## Mark scheme (5 marks)

1. Nichrome (metal) contains free/delocalised electrons
2. These free electrons can move through the metal, carrying charge / forming a current
3. In rubber there are no free/delocalised electrons
4. Because there are no charge carriers in rubber, charge cannot flow / no current can be established
5. Resistance of rubber is (very) high / rubber is an insulator because it has no free charge carriers to allow current to flow

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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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