A rectangular aluminium plate is suspended so that it can swing like a pendulum between the pole pieces of a strong permanent magnet. The plane of the plate is always perpendicular to the direction of swing.
(i) Qualitatively explain, using the appropriate electromagnetic principle, why eddy currents are produced in the plate when it enters and leaves the magnetic field region.
(ii) For each half-swing, predict the direction of the eddy currents in the plate and show how these currents lead to a damping force on the motion.
(iii) Beginning with the expression for mechanical energy of a simple pendulum, explain how repeated action of the damping force leads to a gradual decrease in the amplitude of oscillation. State the form of energy into which the mechanical energy is converted.