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Question: A bar magnet has a magnetic moment equal to \(5 \times 10 ^ { - 5 }\) weber \(\times m\) It is susp...

A bar magnet has a magnetic moment equal to 5×10−55 \times 10 ^ { - 5 } weber ×m\times m It is suspended in a magnetic field which has a magnetic induction (2) equal to The magnet vibrates with a period of vibration equal to 15 sec. The moment of inertia of the magnet is

A

22.5 kg×m222.5 \mathrm {~kg} \times \mathrm { m } ^ { 2 }

B

11.25×kg×m211.25 \times \mathrm { kg } \times \mathrm { m } ^ { 2 }

C

5.62×kg×m25.62 \times \mathrm { kg } \times \mathrm { m } ^ { 2 }

D

Answer

Explanation

Solution

Time period of a magnet

T=2πIMBT = 2 \pi \sqrt { \frac { I } { M B } }

or I=T2MB4π2=225×5×10−5×8π×10−44π2I = \frac { T ^ { 2 } M B } { 4 \pi ^ { 2 } } = \frac { 225 \times 5 \times 10 ^ { - 5 } \times 8 \pi \times 10 ^ { - 4 } } { 4 \pi ^ { 2 } }