# A student investigates how temperature affects the resistance of a thermistor. At room temperature the thermistor has a high resistance. When the thermistor is placed in warm water, its resistance decreases. Explain, in terms of electrons and their movement through the thermistor, why the resistance decreases as temperature increases.

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

> A thermistor is a component whose resistance changes with temperature. At 20 °C its resistance is approximately 10 000 Ω. When heated to 80 °C its resistance falls to around 200 Ω.

## Mark scheme (5 marks)

1. Current is a flow of free electrons (charge carriers) through the thermistor
2. At low temperature there are fewer free electrons available to carry charge
3. As temperature increases, more electrons are released / freed from atoms
4. More free electrons means a greater flow of charge for the same voltage
5. Greater current for the same voltage means resistance is lower (linking to R = V/I or resistance definition)

## Key terms

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

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-investigates-how-temperature-affects-4858e068) · Published by Druglandscape Ltd.