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AQA · GCSE · Combined Science · Higher

Wire length and resistance

Q03.3 2 marks

A student investigated how the resistance of a piece of wire varies with its length. Figure 3 shows the results for five different lengths of the wire.

Graph of resistance of wire in ohms against length of wire in metres. The x-axis runs from 0.00 to 0.60 m. The y-axis runs from 0.0 to about 0.9 ohms. Five plotted points lie on a straight line through the origin, approximately at (0.10, 0.17), (0.20, 0.34), (0.30, 0.51), (0.40, 0.68) and (0.50, 0.85), showing resistance increasing linearly with length.

Figure 3

Enlarged question image

Graph of resistance of wire in ohms against length of wire in metres. The x-axis runs from 0.00 to 0.60 m. The y-axis runs from 0.0 to about 0.9 ohms. Five plotted points lie on a straight line through the origin, approximately at (0.10, 0.17), (0.20, 0.34), (0.30, 0.51), (0.40, 0.68) and (0.50, 0.85), showing resistance increasing linearly with length.
Figure 3

Describe the relationship between the length of the wire and the resistance of the wire.

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Marking points

  1. 1 State that as the length of the wire increases, the resistance increases.
  2. 2 State that the relationship is directly proportional, meaning the graph is a straight line through the origin.

Full-mark answer

The resistance of the wire is directly proportional to its length: as the length increases, the resistance increases in a straight-line relationship through the origin.

Why this answer loses marks

The resistance goes up when the length goes up.

This describes a positive correlation and may gain partial credit, but it does not state direct proportionality.

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