A) 2
B) 1
C) 1/2
D) 1/4
Correct Answer: A
Solution :
Given: Angle of magnet \[(\theta )=90{}^\circ \]and\[60{}^\circ \]. We know that work done in turning the magnet through\[90{}^\circ \]. \[({{W}_{1}})=MB\,(\cos 0{}^\circ -\cos 90{}^\circ )\] \[=MB\,(1-0)=MB.\] Similarly\[{{W}_{2}}=MB\,(\cos 0{}^\circ -\cos 60{}^\circ )\] \[=MB\left( 1-\frac{1}{2} \right)=\frac{MB}{2}.\] Therefore, \[{{W}_{1}}=2\,{{W}_{2}}\]or\[n=2\,.\]You need to login to perform this action.
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