A magnetic needle of magnetic moment `6.7xx10^(-2)A.m^(2)` And moment of inertia `7.5xx10^(-6) "kg".m^(2)` Is performing simple harmonic oscillations in a magnetic field of 0.01 T. time taken for 10 complete oscillations is

Options

A. `6.98s`
B. `8.76s`
C. `6.65s`
D. `8.89s`

Answer

c

Explanation

(c) Given: Magnetic moment , `M=6.7xx10^(-2)Am^(2)`
Magnetic field, `B=0.01T`
Moment of inertia, `I=7.5xx10^(-6) kgm^(2)`
Using, `T=2pisqrt((I)/(MB))`
`=2pi sqrt( (7.5xx10^(-6))/(6.7xx10^(-2)xx0.01))=(2pi)/(10)xx1.06s`
Time taken for 10 complete oscillations
`t=10T=2pixx1.06=6.6568 ~~6.65s`