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BHU PMT BHU PMT (Screening) Solved Paper-2010

  • question_answer
    A wire carrying current i and other carrying 2i in the same direction produce a magnetic field B at the midpoint. What will be the field when 2i current is switched off?

    A)  B/2            

    B)  2B

    C)  B               

    D)  4B

    Correct Answer: C

    Solution :

                     Magnetic field \[{{B}_{1}}=\frac{{{\mu }_{0}}}{4\pi }.\frac{2i}{R}\]and \[{{B}_{2}}=\frac{{{\mu }_{0}}}{4\pi }.\frac{4i}{R}\] \[{{B}_{2}}-{{B}_{1}}=\frac{{{\mu }_{0}}}{4\pi }.\frac{2i}{R}=B\] \[{{B}_{2}}=2{{B}_{1}}\] \[2{{B}_{1}}-{{B}_{1}}=B\] \[{{B}_{1}}=B\]


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