Question

A bar magnet is dropped along the axis of copper ring held horizontally. The acceleration of fall is

• A. equal to g at the place.
• B. less than g.
• C. more than g.
• D. depends upon diameter of the ring and length of the magnet.

Answer 1

The correct option is B less than g.

Since bar magnet is falling, there is a change in the magnetic field in the area taken by the coil.

So, flux changes in the coil.

Since flux = B A
Where, B is magnetic field and A is area.

So, due to change in the flux emf is induced in the coil and by lenz's law current flow in the direction which opposes the change in magnetic field.

So, force due to this current induced magnetic field opposes the motion of bar magnet.

Therefore, net accelearation of fall is less than g.