# A copper connecting wire in a circuit has a low resistance. A student replaces the copper wire with a piece of plastic tubing of the same length and diameter. The plastic tubing has an extremely high resistance. Explain, in terms of the movement of charged particles, why copper has a low resistance and why the plastic tubing has an extremely high resistance.

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

## Mark scheme (5 marks)

1. Copper contains free (delocalised) electrons
2. These free electrons can move through the copper and carry charge / act as charge carriers
3. Because there are many free electrons, current flows easily, so resistance is low
4. Plastic does not have free electrons / charged particles that are free to move
5. Because there are no free charge carriers in plastic, charge cannot flow through it, so resistance is extremely high

## Key terms

- [resistance](https://www.gradenine.co.uk/glossary/resistance)

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/a-copper-connecting-wire-in-a-a81b0149) · Published by Druglandscape Ltd.