Describe the shape of a graph of resistance against temperature for a metallic conductor.

It is a line of positive gradient that is nearly straight over the normal range of laboratory temperatures, so the resistance rises steadily as the temperature is raised.

Describe the shape of a graph of resistance against temperature for a negative temperature coefficient thermistor.

It is a falling curve, very steep at low temperatures and flattening out towards higher temperatures, so equal rises in temperature produce progressively smaller falls in resistance.

CCEA A-Level Physics 1210

Physical Quantities, Scalars and Vectors

Topic overview Physical quantities and SI base units Prefixes and standard form Scalars and vectors Resolving vectors and finding resultants Coplanar forces in equilibrium

Moments and Equilibrium

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Linear Motion and Dynamics

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Resistance and Resistivity

Resistance, temperature and superconductivity

3 things to know
Unit AS 1

Overview

Recall questions on how the resistance of a metal changes with temperature and why, the opposite behaviour of a negative temperature coefficient thermistor and its explanation, the shapes of both graphs, the experiment with a thermistor in a water bath, two uses of a thermistor, and superconductivity with its critical temperature.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How does the resistance of a metallic conductor change as its temperature rises?

Key term

Explain in terms of the structure of a metal why its resistance rises with temperature.

Key term

How does the resistance of a negative temperature coefficient thermistor change as its temperature rises?

Questions from this subtopic

Each one with the model answer underneath.

1
How does the resistance of a metallic conductor change as its temperature rises?
Model answer
The resistance increases, and over a moderate range of temperature the increase is very close to linear.
2
Explain in terms of the structure of a metal why its resistance rises with temperature.
Model answer
Heating makes the positive ions of the lattice vibrate with greater amplitude, so the free electrons collide with them more frequently and lose more energy; the number of free electrons hardly changes, so the drift of charge is impeded and the resistance rises.
3
Describe the shape of a graph of resistance against temperature for a metallic conductor.
Model answer
It is a line of positive gradient that is nearly straight over the normal range of laboratory temperatures, so the resistance rises steadily as the temperature is raised.
4
How does the resistance of a negative temperature coefficient thermistor change as its temperature rises?
Model answer
The resistance falls, and it does so steeply and non-linearly, often by a large factor over only a few tens of degrees.
5
Explain why the resistance of a negative temperature coefficient thermistor falls as it is heated.
Model answer
Heating gives more electrons enough energy to break free and become charge carriers, and this large increase in the number of carriers far outweighs the extra impeding effect of the increased lattice vibration, so the resistance drops.
6
Describe the shape of a graph of resistance against temperature for a negative temperature coefficient thermistor.
Model answer
It is a falling curve, very steep at low temperatures and flattening out towards higher temperatures, so equal rises in temperature produce progressively smaller falls in resistance.

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Resistance, temperature and superconductivity

Overview

What you need to know

How does the resistance of a metallic conductor change as its temperature rises?

Explain in terms of the structure of a metal why its resistance rises with temperature.

How does the resistance of a negative temperature coefficient thermistor change as its temperature rises?

Questions from this subtopic

How does the resistance of a metallic conductor change as its temperature rises?

Explain in terms of the structure of a metal why its resistance rises with temperature.

Describe the shape of a graph of resistance against temperature for a metallic conductor.

How does the resistance of a negative temperature coefficient thermistor change as its temperature rises?

Explain why the resistance of a negative temperature coefficient thermistor falls as it is heated.

Describe the shape of a graph of resistance against temperature for a negative temperature coefficient thermistor.

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Resistance and Resistivity, on a schedule.