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JEE Main & Advanced Physics Electro Magnetic Induction Question Bank Critical Thinking

  • question_answer
    A physicist works in a laboratory where the magnetic field is 2 T. She wears a necklace enclosing area 0.01 m2 in such a way that the plane of the necklace is normal to the field and is having a resistance R = 0.01 W. Because of power failure, the field decays to 1 T in time 10?3 seconds. Then what is the total heat produced in her necklace ? (T = Tesla) [Orissa JEE 2002]

    A)            10 J                                           

    B)            20 J

    C)            30 J                                           

    D)            40 J

    Correct Answer: A

    Solution :

                       \[H=\frac{{{V}^{2}}t}{R}\,and\ \ V=\frac{N({{B}_{2}}-{{B}_{1}})A\cos \theta }{t}\]                    \[V=\frac{1\times (1-2)\times 0.01\times \cos {{0}^{o}}}{{{10}^{-3}}}=10\ V\]            So, \[H=\frac{{{(10)}^{2}}\times {{10}^{-3}}}{0.01}=10\ J\]


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