LDRs & Thermistors
Physics: AQA GCSE Higher, topic 2.2.5
Thermistors and LDRs
Thermistors and LDRs are devices where resistance changes with temperature or light. They can be used as switches for heaters and lights.
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Thermistors
- A thermistor is a component where resistance changes with its temperature.
- Usually, increasing temperature decreases the resistance.
- We can use a thermistor to turn a heater off when a house reaches certain temperatures.
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LDRs
- A light dependent resistor (LDR)s resistance changes with light intensity.
- Usually, increasing light intensity decreases the resistance.
- We can use LDRs to switch lights on when it gets dark or to know whether or not a camera phone needs to use “flash”.
Test yourself on LDRs & Thermistors
If a thermistor is connected in series with a resistor and battery, what will happen in the circuit when the temperature increases?
What effect will increased light intensity have on an LDR?