Magnetic Effects Of Current Question 243
Question: 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 field at two places is
Options:
A) $ 3\sqrt{3:}8 $
B) $ 16:9\sqrt{3} $
C) $ 4:9 $
D) $ 2\sqrt{2}:3 $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ T=2\pi \sqrt{\frac{I}{MB\cos \delta }} $ $ v=\frac{1}{2\pi }\sqrt{\frac{MB\cos \delta }{I}} $ $ v=\sqrt{B\cos \delta } $ or $ B\propto \frac{v^{2}}{\cos \delta } $ $ \frac{B_{1}}{B_{2}}=\frac{400}{\cos 30{}^\circ }\times \frac{\cos 60{}^\circ }{225}=\frac{16\times 2}{9\times \sqrt{3}}\times \frac{1}{2}=16:9\sqrt{3} $
BETA
