JEE Main & Advanced Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव Question Bank Force and Torque on a Current Carrying Conductor

  • question_answer
    A circular coil of radius 4 cm has 50 turns. In this coil a current of 2 A is flowing. It is placed in a magnetic field of 0.1 \[weber/{{m}^{2}}\]. The amount of  work done in rotating it through \[180{}^\circ \] from its equilibrium position will be [CPMT 1977]

    A)            0.1 J                                         

    B)            0.2 J

    C)            0.4 J                                         

    D)            0.8 J

    Correct Answer: A

    Solution :

                       The magnetic moment of current carrying loop                    \[M=niA=ni\,(\pi {{r}^{2}})\]                    Hence the work done in rotating it through 180°                    \[W=MB\,(1-\cos \theta )=2MB\]\[=2(ni\pi {{r}^{2}})B\]            \[=2\times (50\times 2\times 3.14\times 16\times {{10}^{-4}})\times 0.1=0.1J\]


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