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12th Class Physics Magnetism Question Bank MCQ - Magnetism and Matter

  • question_answer
    If a solenoid is having magnetic moment of \[0.65\text{ }J\text{ }{{T}^{-1}}\] is free to turn about the vertical direction and has a uniform horizontal magnetic field of 0.25 T applied. What is the magnitude of the torque on the solenoid when its axis makes an angle of \[30{}^\circ \] with the direction of applied field?

    A) 0.075 Nm                     

    B)             0.080 Nm

    C)             0.081 Nm                     

    D)             0.091 Nm

    Correct Answer: C

    Solution :

    (c) 0.081 Nm. Here,  \[M=0.65\,J\,{{T}^{-1}},B=0.25\,T,\,\theta =30{}^\circ ,\] \[\therefore \tau =MB\,\sin \theta =0.65\times 0.25\times \sin \,30{}^\circ \] \[=0.65\times 0.25\times \frac{1}{2}=0.08125\,Nm\approx 0.081\,Nm\]


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