Question

A magnetic needle has magnetic moment of `6*7xx10^-2Am^2` and moment of inertial of `7*5xx10^-6kgm^2`. It perform `10` complete oscillations in `6*70s`. What is the magnitude of the magnetic field?

Answer 1

Here, `M=6*7xx10^-2Am^2`
`I=7*5xx10^-6kgm^2`
Time for one oscillation,
`T=(6*70)/(10)=0*67s, B=?`
From `T^**=2pisqrt((I)/(MB))`,
`B=(4pi^2I)/(MT^2)=(4xx(22//7)^2xx7*5xx10^-6)/(6*7xx10^-2(0*67)^2)`
`=0*01T`