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  3. RAJASTHAN ­ PET

RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    The work done in turning a magnet of magnetic moment M by angle of \[90{}^\circ \] from the meridian is n times the corresponding work done to turn it through an angle of \[60{}^\circ \] where n is given by

    A)  4               

    B)  2

    C)  1/2             

    D)  1

    Correct Answer: B

    Solution :

     \[{{W}_{1}}=MB(\cos 0{}^\circ -\cos 60{}^\circ )\] \[=MB\left( 1-\frac{1}{2} \right)=\frac{MB}{2}\] \[{{W}_{2}}=MB(\cos 0{}^\circ -\cos 90{}^\circ )=MB\] Given:   \[{{W}_{2}}=n{{W}_{1}}\] \[\therefore \] \[n=2\]


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