Describe how an ammeter and a voltmeter should be connected to the constantan wire to measure its resistance.

The student is advised to switch off the circuit between taking readings at different lengths. Explain how this practice improves the accuracy of the investigation.

To make electrical connections along the wire, the student can use either a wide crocodile clip or a sharp-pointed metal jockey. Explain why using a jockey instead of a crocodile clip improves:

• the resolution of the length measurement
• the accuracy of the calculated resistance.