A bar magnet of length \[I\] and magnetic dipole moment M is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be [NEET 2013] |
A) M
B) \[\frac{3}{\pi }M\]
C) \[\frac{2}{\pi }M\]
D) \[\frac{M}{2}\]
Correct Answer: B
Solution :
[b] The magnetic moment, \[M=ml\] from figure |
\[l=\frac{\pi }{3}\times r\] |
or \[r=\frac{3l}{\pi }\] |
\[\therefore \] New magnetic moment |
\[M'=m\times r\] |
\[=m\times \frac{3l}{\pi }=\frac{3}{\pi }.ml=\frac{3M}{\pi }\] |
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