Resistance of wires – assessed investigationAim: To find out how the length of a wire affects its resistance.What you need to do:• Choose a circuit to use.• Plan your experiment so that it is a FAIR TEST.• Take measurements of resistance for at least 6 different

lengths of wire. Record your results in a table.• Repeat the experiment another 2 times (3 sets of results in

total)• Calculate an AVERAGE resistance for each length of wire.• You could go on to plot graphs of Resistance against length.

The test wire is attached to a metre rule.

Using a resistance meter

Using batteries, voltmeter and ammeter

Using a power supply, voltmeter and ammeter (1)

Using a power supply, voltmeter and ammeter (2)

Using a resistance meter

W

Length, l

Length, l

Advantages• Easy to set up and read.• No problems with the wire

getting hot.• No need to calculate resistance.

DIsadvantages• Maximum grade C.

Using batteries, voltmeter and ammeter

Length, l

Length, l

A V

Advantages• The wire shouldn’t get too hot.• Can achieve up to grade B.

Disadvantages• Maximum grade B.• 2 meters to read. Resistance has

to be calculated• No control over current.• Batteries may go flat.

Using a power supply, voltmeter and ammeter (1)

Length, l

A V

10 W

Length, l

Advantages• The wire shouldn’t get too hot.• Can achieve up to grade A.• More control over voltage and

current.• No batteries to go flat.

Disadvantages• 2 meters to read. Resistance has

to be calculated.• Limited range of voltage and

current.

Using a power supply, voltmeter and ammeter (2)

Length, l

A V

Length, l

Advantages• Quite esy to set up.• Can achieve up to grade A.• Total control over voltage and

current.• No batteries to go flat.

Disadvantages• The wire could get very hot.• 2 meters to read. Resistance has

to be calculated.• Some students find the circuit

more difficult to understand.