Question

A simple pendulum has a small disc shaped magnet as the bob whose magnetic moment is along vertical. Just beneath the bob a current carrying coil is placed on a horizontal table. The coil produces a uniform magnetic field. The dependence of the change in time period |∆T| on current i can be graphically shown as

Answer 1

Correct option  (a)

Explanation:

The magnetic force exerted and hence the corresponding acceleration is proportional to the current. Consider the expression for the period of a simple pendulum in which the effective acceleration due to gravity can be written as

g' = g + ai where a is a constant. Then,

where T₀ is the original period. Therefore, the change in period |ΔT| is linearly proportional to the current i.