Question

The period of oscillation of a magnet in a vibration magnetometer is $2 \sec$. The period of oscillation of a magnet whose magnetic moment is four times that of the first magnet is

• A. $1 \sec$
• B. $5 \sec$
• C. $8 \sec$
• D. $0.5 \sec$

Answer 1

Answer: (A)

$ T =2 \pi \sqrt{\left(\frac{I}{M B_{H}}\right)} $
$ T'=2 \pi \sqrt{\left(\frac{I}{4 M B_{H}}\right)}$
$=\frac{1}{2}\left[2 \pi \sqrt{\frac{I}{\left(M B_{H}\right)}}\right] $
$=\frac{1}{2} \times 2=1$ second