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5.Magnetism and Matter
hard
The magnet of a vibration magnetometer is heated so as to reduce its magnetic moment by $19\%$. By doing this the periodic time of the magnetometer will
A
increase by $19\%$
B
decrease by $19\%$
C
increase by $11\%$
D
decrease by $21\%$
Solution
$T=2 \pi \sqrt{\frac{I}{M B_{H}}} \Rightarrow T \propto \frac{1}{\sqrt{M}} \Rightarrow \frac{T_{1}}{T_{2}}=\sqrt{\frac{M_{2}}{M_{1}}}$
If $M_{1}=100$ than $M_{2}(100-19)=81$
So $\frac{T_{1}}{T_{2}}=\sqrt{\frac{81}{100}}=\frac{9}{10} \Rightarrow T_{2}=\frac{10}{9} T_{1}=1.11 T_{1}$
implies Time period increases by $11 \%$
Standard 12
Physics
