How does the resistivity of a metal change when its temperature increases?

The resistivity of a metal increases with increasing temperature.

Explain at the microscopic level why the resistivity of metals increases with temperature.

Increased temperature causes greater vibration of lattice ions. This increases the frequency of collisions between conduction electrons and the ions, reducing the drift velocity of electrons and therefore increasing resistance.

Explain why the resistivity of a semiconductor decreases when it is heated.

Increasing temperature provides thermal energy that excites more electrons from the valence band to the conduction band, increasing the number of charge carriers available for conduction, which reduces resistivity.

A semiconductor component is placed in a circuit and the surrounding temperature rises significantly. What happens to its resistance and why?

Its resistance decreases because higher temperature increases the number of free charge carriers in the semiconductor, reducing its resistivity.

OCR A-Level Physics A H556

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Energy, Power and Resistance

How resistivity varies with temperature

3 things to know
Papers 2 and 3

Overview

Recall questions on how the resistivity of metals and semiconductors changes with temperature and why, negative temperature coefficients, and NTC thermistors as temperature sensors.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Compare how the resistivity of a semiconductor responds to temperature change versus how a metal responds.

Key term

Explain why the resistivity of semiconductors decreases as temperature rises.

Key term

How does the resistivity of a semiconductor change as its temperature increases?

Questions from this subtopic

Each one with the model answer underneath.

1
How does the resistivity of a metal change when its temperature increases?
Model answer
The resistivity of a metal increases with increasing temperature.
2
Compare how the resistivity of a semiconductor responds to temperature change versus how a metal responds.
Model answer
A semiconductor's resistivity decreases with increasing temperature (more charge carriers are released), whereas a metal's resistivity increases with increasing temperature (increased lattice vibrations impede charge carrier flow).
3
Explain at the microscopic level why the resistivity of metals increases with temperature.
Model answer
Increased temperature causes greater vibration of lattice ions. This increases the frequency of collisions between conduction electrons and the ions, reducing the drift velocity of electrons and therefore increasing resistance.
4
How does the resistivity of a semiconductor change as its temperature increases?
Model answer
The resistivity of a semiconductor decreases with increasing temperature.
5
Explain why the resistivity of a semiconductor decreases when it is heated.
Model answer
Increasing temperature provides thermal energy that excites more electrons from the valence band to the conduction band, increasing the number of charge carriers available for conduction, which reduces resistivity.
6
A semiconductor component is placed in a circuit and the surrounding temperature rises significantly. What happens to its resistance and why?
Model answer
Its resistance decreases because higher temperature increases the number of free charge carriers in the semiconductor, reducing its resistivity.

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