1. Thermistors

2. A thermistor is another special type of resistor
A thermistor is another special type of resistor. Its resistance changes as its temperature changes.
When the temperature of the thermistor is low, its resistance is high. This is because a thermistor is made of a material which does not conduct electricity well at low temperatures. The outer electrons are loosely bound to the atoms and are not free to flow through the thermistor.
As the temperature increases, more outer electrons gain enough energy to break free from atoms. The electrons are then free to flow through the thermistor.

3. This graph shows the thermistor’s resistance against temperature.
Remember, the resistance of a thermistor decreases as the temperature increases.

4. This change in resistance according to their temperature means that thermistors can be used as temperature sensors.
For example, they can be used to warn drivers when the car engine is overheating.

5. Most thermistors have a useful working range of –90 °C to 200 °C.