# A student connects a length of nichrome wire to a battery and measures the current through it. The student then replaces the nichrome wire with a piece of rubber tubing of the same length and cross-sectional area, and finds that almost no current flows. Explain why the nichrome wire conducts electricity but the rubber does not.

> Eduqas A-Level Physics — 2.1 Conduction and resistance · Explain · 5 marks

> Nichrome is a metal alloy used in heating elements. Rubber is commonly used as an electrical insulator.

## Mark scheme (5 marks)

1. Nichrome (as a metal) contains free/delocalised electrons
2. These free electrons can move through the metal when a voltage/potential difference is applied, creating a current
3. In rubber, there are no free/delocalised electrons (electrons are tightly bound to their atoms)
4. Because there are no charge carriers free to move in rubber, no current can flow
5. This makes rubber an electrical insulator (and nichrome/metals conductors) because resistance depends on the availability of free charge carriers

## Related

- [Revision notes for Eduqas A-Level Physics](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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