Magnetism and Matter - Result Question 24
28. Two magnets of magnetic moments $M$ and $2 M$ are placed in a vibration magnetometer, with the identical poles in the same direction. The time period of vibration is $T_1$. If the magnets are placed with opposite poles together and vibrate with time period $T_2$, then
(a) $T_2$ is infinite
(b) $T_2=T_1$
(c) $T_2>T_1$
(d) $T_2<T_1$
[2002]
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Answer:
Correct Answer: 28. (c)
Solution:
- (c) $T_1=2 \pi \sqrt{\frac{I_1+I_2}{(M+2 M) H}}=2 \pi \sqrt{\frac{I}{3 M H}}$
$T_2=2 \pi \sqrt{\frac{I_1+I_2}{(2 M-M) H}}=2 \pi \sqrt{\frac{I}{M H}}$
Obviously, $T_2>T_1$
