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12th Class Physics Magnetism Question Bank MCQ - Moving Charges and Magnetism

  • question_answer
    A circular coil of 25 turns and radius 12 cm is placed in a uniform magnetic field of 0.5 T normal to the plane of the coil. If the current in the coil is 6 A then total torque acting on the coil is:

    A) zero                              

    B) 3.4 N m

    C) 3.8 N m                        

    D) 4.4 N m

    Correct Answer: A

    Solution :

    (a) zero. The torque acting on the coil             \[|\overrightarrow{\tau }|=|\overrightarrow{M}\times \overrightarrow{B}|=MB\sin \theta \] Here the circular coil is placed normal to the direction of magnetic field then the angle between the direction of magnetic moment \[(\overrightarrow{M})\] and magnetic field \[(\overrightarrow{B})\] is zero. Then \[\tau =MB\,\sin \theta =MB\sin 0{}^\circ =0\,\,\therefore \,\,\tau =0\]


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