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A bar magnet with magnetic moment 2.5xx1...

A bar magnet with magnetic moment `2.5xx10^(3)JT^(-2)` is rotating in horizontal plane in the space containing magnetic induction `B=4xx10^(5)T`. The work done in rotating the magnet slowly from a direction parallel to the field to a direction `45^(@)` from the field, is (in joule).

A

0

B

0.2

C

0.03

D

0.02

Text Solution

Verified by Experts

The correct Answer is:
C
The work done (in rotating) by external agent
=change in potential energy
`" " =-MB cos theta_(2)-(-MB cos theta_(1))`
`" " =-MB (cos 45^(@)-cos 0^(@))`
`" " =(1-(1)/(sqrt2))MB=(0.41)/(sqrt2)xx(1)/(10)approx 0.33J`
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