Magnetic Properties of Matter: Practice Problem & Solution
17. Two bar magnets having same geometry with magnetic moments $M$ and $2M$, are firstly placed in such a way that their similar poles are same side then its time period of oscillation is $T_1$. Now the polarity of one of the magnet is reversed then time period of oscillation is $T_2$, then: (2002)
Solution Explained:
To solve this problem, we apply the core principles of Magnetic Properties of Matter. Understanding the underlying formula is key to arriving at the correct answer below:
$T = 2\pi \sqrt{\frac{I}{M_{net} B_H}}$. Initially $M_{net} = 2M + M = 3M$, so $T_1 \propto \frac{1}{\sqrt{3M}}$.
After reversing polarity, $M_{net} = 2M - M = M$, so $T_2 \propto \frac{1}{\sqrt{M}}$. Therefore, $T_1 < T_2$.
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