Question

A magnet is suspended in such a way that it oscillate it horizontal plane.

It make $20$ oscillation per minute at a place were dip angle is $30$ and

$15$ oscillation per minute t a place were dip angle is $60$. the ratio of

total magnetic field at the two place is

• A. $15$ oscillations/minute
• B. $1.7\sqrt{3}$
• C. $18$ oscillations/minute
• D. Zero

Answer 1

The correct option is B $1.7\sqrt{3}$

$\begin{array}{c}Noofoscillation,n=\frac{1}{2\pi }\sqrt{\frac{B\sin \theta }{I}}\\ \frac{20}{15}=\sqrt{\frac{B_1\sin 30}{B_2\sin 60}}\\ \frac{B_1\left(\frac{1}{2}\right)}{B_2\left(\frac{\sqrt{3}}{2}\right)}=\frac{{20}^2\sqrt{3}}{{15}^2}\\ =1.7\sqrt{3}\end{array}$

Hence,

option $B$ is correct answer.