Punjab Medical Punjab - MET Solved Paper-2007

  • question_answer
    A square wire of each side I carries a current J. What is the magnetic field at the midpoint of the square?

    A) \[4\sqrt{2}\frac{{{\mu }_{0}}}{4\pi }\frac{I}{l}\]                 

    B) \[8\sqrt{2}\frac{{{\mu }_{0}}}{4\pi }\frac{I}{l}\]

    C) \[16\sqrt{2}\frac{{{\mu }_{0}}}{4\pi }\frac{I}{l}\]                               

    D) \[32\sqrt{2}\frac{{{\mu }_{0}}}{4\pi }\frac{I}{l}\]

    Correct Answer: B

    Solution :

    \[B=4\left[ \frac{{{\mu }_{0}}}{4\pi }\cdot \frac{I}{a}(\sin {{\phi }_{1}}+\sin {{\phi }_{2}}) \right]\]                 \[=4\times \frac{{{\mu }_{0}}}{4\pi }\frac{I}{(l/2)}\left[ \frac{1}{\sqrt{2}}+\frac{1}{\sqrt{2}} \right]\]                                    (Here,\[a=\frac{l}{2},\,\,{{\phi }_{1}}={{\phi }_{2}}={{45}^{o}}\])                 \[=4\times \frac{16}{\sqrt{2}}\left[ \frac{{{\mu }_{0}}}{4\pi }\frac{I}{l} \right]\]                 \[=8\sqrt{2}\left( \frac{{{\mu }_{0}}}{4\pi }\frac{I}{l} \right)\]


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