Magnetism Question 117
Question: The magnet of a vibration magnetometer is heated so as to reduce its magnetic moment by 19%. By doing this the periodic time of the magnetometer will
[MP PMT 2000, 01]
Options:
A) Increase by 19%
B) Decrease by 19%
C) Increase by 11%
D) Decrease by 21%
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Answer:
Correct Answer: C
Solution:
$ T=2\pi \sqrt{\frac{I}{MB _{H}}}\Rightarrow T\propto \frac{1}{\sqrt{M}}\Rightarrow \frac{T _{1}}{T _{2}}=\sqrt{\frac{M _{2}}{M _{1}}} $ If M1 =100 than M2 (100 ? 19) = 81 So $ \frac{T _{1}}{T _{2}}=\sqrt{\frac{81}{100}}=\frac{9}{10}\Rightarrow T _{2}=\frac{10}{9}T _{1}=1.11T _{1} $
$ \Rightarrow $ Time period increases by 11%
BETA
