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A bar magnet is held at a right angle to...

A bar magnet is held at a right angle to a uniform magnetic field. The couple acting on the magnet is to be halved by rotating it from the position. The angle of rotation is

A

`60^(@)`

B

`45^(@)`

C

`30^(@)`

D

`75^(@)`

Text Solution

Verified by Experts

As, `tau=MB sintheta`
Where, `theta=90^(@) Rightarrow tau=MB`
`tau_(2)=(1)/(2)tau_(1) Rightarrow MB sintheta=(1)/(2)MB Rightarrow sin theta =(1)/(2) Rightarrow theta=30^(@)`
`therefore "Angle of rotation"=90^(@)-30^(@)=60^(@)`
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