A student is investigating how the resistance of a wire depends on its length.

Resistance $R$ is given by the equation $R=\frac{V}{I}$.

The following apparatus is available to the student:

• ammeter
• voltmeter
• low-voltage d.c. power supply
• metre ruler
• resistance wire of uniform diameter
• sliding contacts (crocodile clips)
• variable resistor
• switch
• connecting leads

Plan an experiment to investigate how the resistance of the wire depends on its length. You are not required to carry out this investigation.

You should:

• draw a diagram of the circuit you would use to determine the resistance of the wire for different lengths
• explain briefly how you would carry out the investigation, including the measurements you would take
• state the key variables that you would control
• draw a suitable table, with column headings, to show how you would display your readings (you are not required to enter any readings in the table).