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Temperature dependence of resistance
Intermediate
Metals' resistance rises with temperature.
R = R₀(1+αΔT)Metal resistance rises with temperature: R = R₀(1 + αΔT), because lattice vibrations scatter electrons more. Semiconductors' resistance falls with temperature.
Tungsten filament at 2500 °C has about 12 times the cold resistance.
Cold start-up currents are therefore large.
In more detail
For most metals, resistance increases with temperature because atomic vibrations scatter electrons more. Semiconductors often show the opposite trend.
Real-world uses
- Platinum resistance thermometers measure temperature by resistance.
- Tungsten filaments have higher resistance when hot.
- A filament lamp has a much higher resistance when hot than when cold, which is why it draws a large current when switched on.
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Frequently asked questions
Why does heating increase metal resistance?
Hotter atoms vibrate more and scatter electrons more often.
Why do semiconductors behave differently?
More charge carriers are released at higher temperatures, which lowers resistance.
Why does metal resistance rise with temperature?
The atoms vibrate more strongly, so electrons are scattered more often, which reduces their average drift.
Related topics in Current Electricity & Circuits
Resistance · Resistivity · Conductivity · Superconductors · Semiconductors and thermistors · Resistors in series