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

Answer

A

Explanation

`T = 2pi sqrt( (I)/(MB))`
` = 2 xx 3.14 sqrt( (7.5 xx 10^(-6) )/(6.7 xx 10^(-2) xx 10^(-2) ) ) `
T = 0.665 sec
for 10 oscillations , time taken is
` T. = 10 xx T = 6.65 s`