A bar magnet is held at right angle to a uniform magneitc field. The couple acting on the acting on the magnet is to be halved by rotating it form this position. The angle of rotation isA. `60^(@)`B. `45^(@)`C. `30^(@)`D. `75^(@)`

A bar magnet is held at right angle to a uniform magneitc field. The c

1.	A bar magnet is held at right angle to a uniform magneitc field. The couple acting on the acting on the magnet is to be halved by rotating it form this position. The angle of rotation isA. `60^(@)`B. `45^(@)`C. `30^(@)`D. `75^(@)`
Answer» 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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A bar magnet is held at right angle to a uniform magneitc field. The couple acting on the acting on the magnet is to be halved by rotating it form this position. The angle of rotation isA. `60^(@)`B. `45^(@)`C. `30^(@)`D. `75^(@)`

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