Year 10 - Science
LDRs and thermistors
Circuit components
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit explores current, resistance, and potential difference. It covers circuit design for lamps, diodes, and thermistors, and emphasises planning experiments, data interpretation, and presenting scientific conclusions.
Lesson Summary
You will learn to describe how an LDR or a thermistor can be used in a sensing circuit.
Key Notes
- An LDR is made of a semiconductor, and the brighter the light shining on it, the lower its resistance.
- Light transfers energy that enables electrons in a semiconductor to move as they do in a metal conductor.
- A thermistor is made of a semiconductor, and the hotter it is, the lower its resistance.
- Heating transfers energy that enables electrons in a semiconductor to move as they do in a metal conductor.
- A potential divider circuit can be set up with an LDR/thermistor to trigger a switch if it becomes too dark or too cold.
Vocabulary To Learn
- light-dependent resistor: a semiconducting component with a resistance that gets lower in increasingly bright light
- semiconductor: a material that has both metallic and non-metallic properties
- thermistor: a semiconducting component with a resistance that gets lower in increasingly high temperatures
- potential divider: a series circuit that divides the p.d. across a power supply into two or more smaller voltages
Common Mistakes To Avoid
- Circuits are analysed sequentially, starting at the battery and working round, one component at a time.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
An LDR is made of a semiconductor, and the brighter the light shining on it, the lower its resistance. Light transfers energy that enables electrons in a semiconductor to move as they do in a metal conductor.
2. Define this scientific word and use it in context. 'light-dependent resistor'
a semiconducting component with a resistance that gets lower in increasingly bright light. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Circuits are analysed sequentially, starting at the battery and working round, one component at a time. Correction: Ask questions that prompt pupils to consider the effect of changes to one component on the whole circuit.
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