Magnetism Question 118
Question: A magnet makes 40 oscillations per minute at a place having magnetic field intensity of 0.1 ´ 10?5 T. At another place, it takes 2.5 sec to complete one vibration. The value of earth’s horizontal field at that place is
[AIIMS 2000; CPMT 2000; Pb PET 2002]
Options:
A) 0.25 ´ 10?6 T
B) 0.36 ´ 10?6 T
C) 0.66 ´ 10?8 T
D) 1.2 ´ 10?6 T
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Answer:
Correct Answer: B
Solution:
$ T=2\pi \sqrt{\frac{I}{M\times B _{H}}}\Rightarrow T\propto \frac{1}{\sqrt{B _{H}}} $
$ \Rightarrow \frac{T _{1}}{T _{2}}=\sqrt{\frac{{{(B _{H})} _{2}}}{{{(B _{H})} _{1}}}}\Rightarrow \frac{60/40}{2.5}=\sqrt{\frac{{{(B _{H})} _{2}}}{0.1\times {{10}^{-5}}}} $
$ \Rightarrow {{(B _{H})} _{2}}=0.36\times {{10}^{-6}}T $
BETA
