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

  • question_answer
    A small circular flexible Loop of wire of radius r carries a current l. It is placed in a uniform magnetic field B. The tension in the loop will be doubled if:

    A) l is doubled                   

    B) B is halved

    C) r is doubled                   

    D) both B and l are doubled

    Correct Answer: A

    Solution :

    (a) l is doubled. M = lA when l is doubled, M is doubled. Also, \[\tau =MB\,\sin \theta ,\] when M is doubled, torque is doubled, hence tension is doubled.


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