Force on a current-carrying conductor — Describe

Describe an experiment to show that a force acts on a current-carrying conductor in a magnetic field, and describe the effect of reversing (a) the current and (b) the direction of the field.

Place a straight wire, free to move (e.g. resting on horizontal conducting rails), between the poles of a strong magnet so it lies at right angles to the field. When a current flows through the wire, it experiences a force and moves in a direction perpendicular to both the current and the field, as predicted by Fleming's left-hand rule. (a) Reversing the direction of the current reverses the direction of the force. (b) Reversing the direction of the magnetic field (e.g. turning the magnet round) also reverses the direction of the force.