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Semiconductors and thermistors
Intermediate
Resistance falls as temperature rises.
Semiconductors (silicon, germanium) have few carriers at low temperature; heating releases more, so resistance drops. NTC thermistors exploit this for temperature sensing.
Thermistors in digital thermometers.
Doping controls conductivity.
In more detail
Semiconductors have resistance that falls as temperature rises, because more charge carriers are freed. Thermistors use this property to measure temperature.
Real-world uses
- Thermistors measure temperature in ovens and car engines.
- Silicon chips are built from semiconductors that switch current on and off.
- A thermistor in a thermostat uses falling resistance with heat to sense temperature and switch a heater on or off.
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Frequently asked questions
What is a thermistor?
A resistor whose resistance changes strongly with temperature.
Are semiconductors conductors or insulators?
They lie between the two, and their conductivity can be controlled.
Why do semiconductors behave differently from metals?
More charge carriers become free as temperature rises, which lowers the resistance rather than raising it.
Related topics in Current Electricity & Circuits
Conductivity · Temperature dependence of resistance · Superconductors · Resistors in series · Resistors in parallel · Colour code of resistors