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A magnet of magnetic moment M is situate...

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 `180^(@)` will be

A

` - MB`

B

`+ MB`

C

zero

D

` + 2 MB`

Text Solution

Verified by Experts

The correct Answer is:
D
Work done in rotating the magnet from angle `theta_(1) "to angle" theta_(2)` is given by,
`W=MB(costheta_(1)-costheta_(2))`
`Here, theta_(1)=0^(@) and theta_(2)=180^(@)`
`W=MB(cos 0^(@)-cos 180^(@))=2MB`
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