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NEET NEET SOLVED PAPER 2017

  • 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

    A)  \[1.15\,\mu J\]                

    B) \[9.1\,\mu J\]

    C)   \[4.55\,\mu J\]                               

    D)  \[2.3\,\mu J\]

    Correct Answer: B

    Solution :

                     \[W=MB(cos{{\theta }_{1}}-cos{{\theta }_{2}})\] 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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