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

  • question_answer
    Two wires are kept parallel and carry equal currents separated by 2 cm apart. They experience an attractive force of \[16\times {{10}^{-5}}\] newton per unit length, find the current flowing in the two wires.

    A) \[16\times {{10}^{-5}}A\]                    

    B) \[16A\]

    C) \[4A\]                           

    D) \[1A\]

    Correct Answer: C

    Solution :

    (c) \[4A\] Here \[{{l}_{1}}={{l}_{2}}=l,\,F=16\times {{10}^{-5}}N/m,\,d=2\,cm\] \[F=\frac{{{\mu }_{0}}2{{l}_{1}}{{l}_{2}}}{4\pi d}=\frac{{{\mu }_{0}}}{4\mu }\frac{2{{l}^{2}}}{d}\] \[16\times {{10}^{-5}}={{10}^{-7}}\times \frac{2\times {{l}^{2}}}{2\times {{10}^{-2}}}\] \[\Rightarrow {{l}^{2}}=\frac{16\times {{10}^{-5}}}{{{10}^{-5}}}=16\Rightarrow l=4\,A\].


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