# A filament lamp and a fixed resistor are connected in series with a battery. Describe how the resistance of the filament lamp changes as it is switched on and reaches its normal operating temperature, and explain why this change occurs.

> Cambridge International IGCSE Physics (0625) — 4.3 Electric circuits · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. The resistance of the filament lamp increases as it reaches normal operating temperature.
2. The filament's temperature increases as current flows through it / the filament gets hotter.
3. The higher temperature causes greater resistance (the resistance increases as the filament's temperature increases).
4. Therefore, the current through the circuit decreases as the lamp warms up / the current is lower at normal operating temperature than when first switched on.

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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-filament-lamp-and-a-fixed-d18d8079) · Published by Druglandscape Ltd.