# A student investigates how resistance changes with temperature for two components: a thermistor and a fixed resistor. As the temperature of both components is increased from 0 °C to 60 °C, describe and explain the differences in how the resistance of each component changes.

> Edexcel A-Level Physics (9PH0) — 10.1 Stars, life cycles and cosmology · Describe and explain · 5 marks

> A thermistor and a fixed resistor are each connected separately to identical circuits, each with a constant voltage supply, an ammeter in series, and a voltmeter in parallel. The temperature of each component is gradually increased from 0 °C to 60 °C.

## Mark scheme (5 marks)

1. The resistance of the thermistor decreases as temperature increases
2. The resistance of the fixed resistor stays (approximately) constant / does not change significantly with temperature
3. In the thermistor, higher temperature means charge can flow more easily / fewer collisions between electrons and ions (accept: more charge carriers available)
4. For the fixed resistor (or a normal conductor), as temperature increases, ions vibrate more, causing more collisions with electrons, which would tend to increase resistance
5. Therefore the thermistor is useful as a temperature sensor / thermostat because its resistance changes significantly with temperature, whereas the fixed resistor is not temperature-sensitive

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-student-investigates-how-resistance-changes-9125729e) · Published by Druglandscape Ltd.