Magnetism Question 99
Question: A bar magnet has a magnetic moment equal to $ 5\times {{10}^{-5}}weber\times m. $ It is suspended in a magnetic field which has a magnetic induction equal to $ 8\pi \times {{10}^{-4}}tesla. $ The magnet vibrates with a period of vibration equal to 15 sec. The moment of inertia of the magnet is
[MP PMT 1993; CBSE PMT 2001]
Options:
A) $ 22.5kg\times m^{2} $
B) $ 11.25\times kg\times m^{2} $
C) $ 5.62\times kg\times m^{2} $
D) $ 7.16\times {{10}^{-7}}kg-m^{2} $
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Answer:
Correct Answer: D
Solution:
Time period of a magnet $ T=2\pi \sqrt{\frac{I}{MB}} $ or $ I=\frac{T^{2}MB}{4{{\pi }^{2}}}=\frac{225\times 5\times {{10}^{-5}}\times 8\pi \times {{10}^{-4}}}{4{{\pi }^{2}}} $
$ \
Therefore \ I=7.16\times {{10}^{-7}}kg-m^{2} $
BETA
