For a circuit that you would use to determine the resistance of a coil of wire using a voltmeter and an ammeter. State the equation you would use to calculate the resistance of the coil.

In the diagram, $AB$ is a $0.2 \mathrm{m}$ length of uniform resistance wire, connected into a circuit. Ignore the resistance of the battery.

The current $I$ is $1.5 \mathrm{A}$. Calculate the resistance per metre of the resistance wire in $\mathrm{\Omega }/\mathrm{m}$.