# Explain why the resistance of a metallic conductor increases as its temperature increases.

> IB DP Physics Standard Level (2023 syllabus) — B.5 Current and circuits · Explain · 4 marks

## Mark scheme (4 marks)

1. A metallic conductor contains a lattice of positive ions (and a 'sea' of delocalised/free electrons).
2. As temperature increases, the positive ions vibrate with greater amplitude.
3. The more vigorously vibrating ions present a greater effective cross-sectional obstruction, so free electrons collide with (or are scattered by) the ions more frequently.
4. More frequent collisions reduce the mean drift velocity of the electrons for the same applied potential difference, meaning the current decreases and hence resistance (R = V/I) increases.

## Key terms

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

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](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/explain-why-the-resistance-of-a-5dac9cfb) · Published by Druglandscape Ltd.