Magnetism Question 173
Question: A magnet of magnetic moment M is situated with its axis along the direction of a magnetic field of strength B. The work done in rotating it by an angle of 180o will be
[MP PMT 1985; MP PET 1997]
Options:
A) $ -MB $
B) $ +MB $
C) 0
D) $ +2MB $
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Answer:
Correct Answer: D
Solution:
Work done $ MB(\cos {\theta _{1}}-\cos {\theta _{2}}) $
$ {\theta _{1}}=0^{o} $ and $ {\theta _{2}}=180^{o} $
$ \Rightarrow W=MB( \cos 0-\cos 180 )=2MB $
BETA
