# A student connects a light dependent resistor (LDR) in series with a fixed resistor and a battery. The student then covers the LDR so that no light reaches it. Explain what happens to the potential difference across the fixed resistor when the LDR is covered.

> AQA A-Level Physics (7408) — 3.5.1 Current Electricity · Explain · 5 marks

## Mark scheme (5 marks)

1. Covering the LDR increases its resistance
2. Total resistance of the circuit increases
3. Current in the circuit decreases
4. Potential difference across the fixed resistor decreases
5. Because the potential difference across a component depends on both the current through it and its resistance (V = IR), and the current has decreased whilst the fixed resistance is unchanged

## Key terms

- [light dependent resistor (LDR)](https://www.gradenine.co.uk/glossary/light-dependent-resistor-ldr)
- [potential difference](https://www.gradenine.co.uk/glossary/potential-difference)
- [series](https://www.gradenine.co.uk/glossary/series)

## Related

- [Revision notes for AQA A-Level Physics (7408)](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/a-student-connects-a-light-dependent-200fde96) · Published by Druglandscape Ltd.