Question

GENERAL PHYSICS (PHYS 2001 Cutnell, Physics, 10e The drawing shows a bar magnet falling through a metal ring. In part a the ring is solid all the way around, but in part b it has been cut through 19

Part (a) explain why the notion of the magnet in part a is retarded when the magnet is above the ring and below the ring as well

**draw any induced currents that appear in the ring**

Part (b) explain why the motion of the magnet is unaffected by the ring in part b

Answer 1

(a) Applying Lenz’s Law, the falling magnet is increasing the flux downward in the ring.  Thus producing the current as drawn.  But the current produces an induced magnetic field (as drawn).  Thus the induced field is always opposite of the field created by the bar magnet causing an repulsive force between the ring and the bar magnet, thus slowing the magnet. As the magnet passed through the ring, the flux is growing smaller, thus the direction of induced magnetic field is reversed still causing an attractive force\ between the bar magnet and the ring.

Simply put, in part b, the ring is broken so no current flows, therefore without a current, there is no induced magnetic field even though there is still a changing flux in the ring