ELECTRICAL RESISTANCE

3 marks · Normal

Describe an experiment you could carry out to investigate how the current in a wire changes as the voltage across it increases. Include the circuit used, what you would measure, and how you would present the results.

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Set up a circuit with a wire, a variable resistor, an ammeter in series, and a voltmeter across the wire. Change the voltage using the variable resistor. For each voltage value, measure the corresponding current. Record results in a table and plot a graph of current versus voltage.

Also accept: Use a circuit with a power supply, wire under test, variable resistor, ammeter and voltmeter. Vary the voltage and measure current. Record and plot current against voltage.

Common mistakes: not including voltmeter/ammeter placement; not mentioning graph/table

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Marking points

M1 · 1 mark · Describes suitable circuit/apparatus (wire, variable resistor, ammeter, voltmeter).

M2 · 1 mark · States that both voltage and current are measured for various values.

B1 · 1 mark · Mentions recording results in a table and/or plotting current versus voltage graph.

Worked solution

Set up a circuit including the wire to be tested, variable resistor, ammeter in series and voltmeter in parallel with the wire. Vary the resistance to change voltage across the wire and measure resulting current. Record each pair of voltage/current readings. Present the results in a table and plot a graph of current (y-axis) against voltage (x-axis).