First slide
Magnetism
Question

In figure, the magnetic needle has magnetic moment 6.7x10-2 Am2 and moment of inertia 7.5x10-6 kgm2. It perform10 complete oscillations in 6.70s. What is the magnitude of the magnetic field? ………………. T.

Moderate
Solution

Given : M=  6.7×10-2 Am2  , I=7.5×10-6 kgm2 , n=106.7Hz

frequecy of oscillation =n=12πMBI    [where M=Magnetic Moment ,I = Moment of Inertia]

B=4π2n2IM=4π2×102×7.5×10-66.72×6.7×10-2=0.01T

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