The magnet of a vibration magnetometer is heated so as to reduce its magnetic moment by `19%`. By doing this the period time of the magnetometer will

Options

A. Increase by `19%`
B. Decrease by `19%`
C. Increase by `11%`
D. Decrease by `21%`

Answer

C

Explanation

`T=2pisqrt(I/(MB_(H)))impliesTprop1/sqrt(M)impliesT_(1)/T_(2)=sqrt(M_(2)/M_(1))`
If `M_(1)=100` than `M_(2)(100-19)=81`
So `T_(1)/T_(2)=sqrt(81/100)=9/10implies T_(2)=10/9T_(1)=1.11T_(1)`
implies Time period increases by `11%`