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

  • question_answer
    In a moving coil galvanometer the deflection \[(\phi )\] on the scale by a pointer attached to the spring is:

    A) \[\left( \frac{NA}{kB} \right)l\]                 

    B) \[\left( \frac{N}{kAB} \right)l\]

    C) \[\left( \frac{NAB}{k} \right)l\]                 

    D) \[\left( \frac{NAB}{kl} \right)\]

    Correct Answer: C

    Solution :

    (c) \[\left( \frac{NAB}{k} \right)l\] Since magnetic torque on the coil, \[\tau =\text{ }NlAB\] This torque is balanced by counter torque             \[\therefore k\phi =NlAB\] or \[\phi =\left( \frac{NAB}{k} \right)l\] where k is torsional constant. It is a scalar quantity having dimension of torque or energy i.e.,             \[[M{{L}^{2}}{{T}^{-2}}]\].


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