Question

Consider a metal ring kept on a horizontal plane. A bar magnet is held above the ring with its length along the central axis of the ring. If the magnet is now dropped freely, the acceleration of the falling magnet is (g is acceleration due to gravity)

• A. More than g
• B. Equal to g
• C. Less than g
• D. Depends on mass of magnet

Answer 1

Answer: (C)

Less than g

Answer 2

When the magnet is allowed to fall vertically along the axis of loop with its north pole towards the ring. The upper face of the ring will become north pole in an attempt to oppose the approaching north pole of the magnet. Therefore the acceleration in the magnet is less than g.

Note : If the coil is broken at any point then induced emf will be generated in it but no induced current will flow. In this condition the coil will not oppose the motion of magnet and the magnet will fall freely with acceleration g. (i.e. a = g)