Magnetism Question 88
Question: Two bar magnets of the same mass, length and breadth but magnetic moments M and 2M respectively, when placed in same position, time period is 3 sec. What will be the time period when they are placed in different position
[NCERT 1977; DPMT 1999]
Options:
A) $ \sqrt{3}\sec $
B) $ 3\sqrt{3}\sec $
C) $ 3\sec $
D) $ 6\sec $
Show Answer
Answer:
Correct Answer: B
Solution:
In sum position $ T\propto \frac{1}{\sqrt{M _{1}+M _{2}}} $ and in difference position $ T\propto \frac{1}{\sqrt{M _{1}-M _{2}}} $
$ \Rightarrow \frac{3^{2}}{T^{2}}=\frac{2M-M}{2M+M}\Rightarrow T^{2}=9\times 3{{\sec }^{2}} $
$ \
Therefore \ T=3\sqrt{3}\sec $
BETA
