A magnetic needle is free to oscillate in a uniform magnetic field as shown in the figure. The magnetic moment of magnetic needle `7.2Am^(2)` and moment of inertia `I=6.5xx10^(-6)kgm^(2)`. The number of oscillation performed in 5s os 10. Calculate the magnitude of magnetic field?
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Here, `T=("Number of revolutions")/("Time taken")=(5)/(10)=0.5s`
`" " M=7.2Am^(2),I=6.5xx10^(-6)kgm^(2)`
`As, " " T=2pi sqrt((I)/(MB)) or T^(2)=4pi^(2)(I)/(MB)`
The magnetude of the magnetic field is
`" " B=(4pir^(2)I)/(MT^(2))=(4xx(3.14)^(2)xx6.5xx10^(-6))/(7.2xx(0.5)^(2))=1.42xx10^(-4)T`
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