(a)[2]
State Lenz’s law in words.
(b)[4]
A metal ring is hung from a fixed point $P$ by a thread, as shown in Fig. 10.1. The ring is moved a distance $d$ and then released. It makes many oscillations before stopping. The poles of a magnet are then brought close to the ring so that the ring hangs midway between the poles of the magnet, as shown in Fig. 10.2. The ring is again moved a distance $d$ and released. Explain why the ring makes fewer oscillations before coming to rest.
(c)[3]
The ring in (b) is now cut so that it has the shape shown in Fig. 10.3. Explain why, when the procedure in (b) is repeated, the cut ring makes more oscillations than the complete ring when it oscillates between the poles of the magnet.