The diagram below shows two long, vertical parallel current-carrying wires, $X$ and $Y$.

Draw on this

The current in wire $X$ is directed upwards, and the current in wire $Y$ is directed downwards.

Explain why wire $Y$ experiences a force and deduce the direction of this force.

State Lenz's law of electromagnetic induction.

Describe how a student can perform an experiment in the laboratory to show that the peak electromotive force (e.m.f.) $V_0$ induced in a small search coil placed at the centre of a long solenoid is directly proportional to the frequency $f$ of the alternating current in the solenoid, assuming the peak current in the solenoid is kept constant.