A set-up was used to investigate the relationship between the length of a wire and its resistance. The voltmeter measured the potential difference across different lengths of the wire.

Length (cm) / Voltage (V) / Resistance (Ω): 0 / 0 / 0; 15.0 / 2.0 / 2; 30.0 / 4.0 / 4; 45.0 / 6.0 / ?; 60.0 / 8.0 / 8; 90.0 / 12.0 / 12. (Plot the graph on paper.)

1. aThe current was 1.0 A. Calculate the resistance at the 45.0 cm mark, using R = V ÷ I. [1]
2. bUsing your graph, find the resistance when the sliding contact is at the 75.0 cm mark. Show your working. [2]
3. cWhat conclusion can be drawn from the investigation? [1]
4. dState one factor which affects the resistance of a wire apart from its length. [1]
5. eWhich instrument is used to measure current? [1]

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