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

  • question_answer
    A circular current loop of magnetic moment M is in an arbitrary orientation in an external magnetic field B. The work done to rotate the loop by \[{{30}^{\operatorname{o}}}\] about an axis perpendicular to its plane is

    A) MB

    B) \[\frac{\sqrt{3}\operatorname{MB}}{2}\]

    C) \[\frac{\operatorname{MB}}{2}\]

    D) zero.

    Correct Answer: D

    Solution :

    Option [d] is correct
    Explanation: The work done to rotate the loop in magnetic field, \[W=MB(cos{{\theta }_{1}}-cos{{\theta }_{2}})\].
    When current carrying coil is rotated then there will be no change in angle between magnetic moment and magnetic field.
    Here, \[{{\theta }_{1}}={{\theta }_{2}}=\alpha \]
    \[\Rightarrow W=MB\] \[\left( cos\ \alpha ~-\text{ }cos\ \alpha  \right)\] = 0.
     


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