Question

A short magnet is allowed to fall from rest along the axis of a horizontal conducting ring. The distance fallen by the magnet in one second may be

• A. $5m$
• B. $6m$
• C. $4m$
• D. None of these

Answer 1

The correct option is C $4m$

Free fall of magnet w/o ring
$d=\frac{1}{2}g{t}^2$
$d=0.5\times 10\times 1^2=5m$
Lenz's law states that current is induced to oppose the change in magnetic field, hence a repulsive force on the magnet is exerted by the ring below
thus
$a<g$
hence
$d<\frac{1}{2}g{t}^2$
$d<5m$