# A copper connecting wire and a thin pencil lead (graphite) are both used in electrical circuits. Describe and explain the difference in resistance between the copper wire and the pencil lead, referring to the structure of each material and how charge carriers move through them.

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

> Copper is a metal widely used for electrical wiring. Graphite (pencil lead) is a non-metal that can also conduct electricity, but it has a noticeably higher resistance than a copper wire of the same dimensions.

## Mark scheme (5 marks)

1. Copper has a lower resistance than graphite (pencil lead)
2. Copper contains many free (delocalised) electrons that can move through the metal
3. In graphite, fewer free electrons are available / charge carriers are fewer in number
4. Fewer charge carriers means current is harder to drive through graphite, so resistance is higher
5. Electrons (charge carriers) collide with the lattice / ions / atoms as they move, and more frequent or more obstructed collisions in graphite increase its resistance

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-copper-connecting-wire-and-a-c50915fb) · Published by Druglandscape Ltd.