A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating; it is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to

• development of air current when the plate is placed.

• induction of electrical charge on the plate

• shielding of magnetic lines of force as aluminium is a paramagnetic material.

• electromagnetic induction in the aluminium plate giving rise to electromagnetic damping.