Thermistors and LDRs: how sensor circuits work
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The key ideas and the summary sheet for this lesson are ready now.
Key ideas
A thermistor's resistance goes down as its temperature goes up.
An LDR's resistance goes down as the light on it gets brighter.
Both are used as sensors, for example in a thermostat or a light that turns on when it gets dark.
In a series circuit, the sensor's share of the p.d. changes as its resistance changes.