Question

A coil is suspended in 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:

• A. Electromagnetic induction in the aluminium plate giving rise to electromagnetic damping
• B. Development of air current when the plate is placed.
• C. induction of electrical charge on the plate
• D. Shielding of magnetic lines of force as aluminium is a paramagnetic material.

Answer 1

The correct option is D Shielding of magnetic lines of force as aluminium is a paramagnetic material.

$\left(D\right)$ option is correct. The oscillating coil produces time variable magnetic field. It causes eddy current in the aluminium plate which causes anti-torque on the coil, due to which it stops. Thus, electromagnetic induction in the aluminium plate giving rise to electromagnetic damping.