NEET Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव NEET PYQ-Magnetic Effects Of Current

  • question_answer
      A 250-Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of \[85\,\mu A\] and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by \[{{180}^{o}}\] against the torque is         [NEET-2017]

    A)  \[1.15\,\mu J\]  

    B)       \[9.1\,\mu J\]

    C)  \[4.55\,\mu J\]  

    D)       \[2.3\,\mu J\]

    Correct Answer: B

    Solution :

    [b] \[W=MB(cos{{\theta }_{1}}-cos{{\theta }_{2}})\]
    When it is rotated by angle \[{{180}^{o}}\] then
    \[W=2MB\]
    \[W=2(NIA)B\]
    \[=2\times 250\times 85\times {{10}^{-6}}[1.25\times 2.1\times {{10}^{-4}}]\times 85\]
    \[\times {{10}^{-2}}\]
    \[=9.1\,\mu J\]


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