1. Tardigrade
  2. Question
  3. Physics
  4. A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a plane where dip angle is 30° and 15 oscillations per minute at a place where dip angle is 60° . The ratio of earth's magnetic fields at two places is

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a plane where dip angle is $30^\circ $ and 15 oscillations per minute at a place where dip angle is $60^\circ $. The ratio of earth's magnetic fields at two places is

AFMCAFMC 2011Magnetism and Matter

Solution:

Time period of suspended magnet $ T=2\pi\sqrt{\frac{i}{MB\cos \delta}}$ $ v=\frac{1}{2\pi}\sqrt{\frac{MB\cos \delta}{i}}$ $ v \propto \sqrt{B\cos \delta}$ or $ B \propto\frac{v^2}{\cos\, \delta}$ $\therefore \frac{B_1}{B_2}=\frac{400}{\cos\, 30^\circ}\times\frac{\cos\, 30^\circ}{225}$ $ =\frac{16\times 2}{9\times\sqrt{3}}\times\frac{1}{2}=16: 9\sqrt{3}$