Question

Two bar magnets having the same geometry with magnetic moments M and 2M are firstly placed in such a way that their similar poles are same side then their time period of oscillation is T1. Now the polarity of one of the magnets is reversed the time period of oscillation is T2, then

• A. T1 < T2
• B. T1 = T2
• C. T1 > T2
• D. T2 = ∞

Answer 1

Answer: (A)

T1 < T2

Answer 2

The correct option is (A) : T1 < T2

T = $2\pi\sqrt{\frac{1}{MB}}$ $\Rightarrow$ $T\propto\frac{1}{\sqrt M}$

case I : M1 = 2M + M

case II : M2 = 2M – M $\frac{T_1}{T_2}$=$\sqrt{\frac{M}{3M}}$=$\frac{1}{\sqrt3}$ ⇒ T2 = $\sqrt3$T1