Haryana PMT Haryana PMT Solved Paper-2004

  • question_answer
    An infinitely long straight conductor is bent into the shape as shown in figure. It carries a current \[i\] A and radius of the circular loop is \[r\] m. The magnetic field at the centre of the loop is :

    A)                 \[{{\mu }_{0i}}(\pi -1)2\pi r\]     

    B) \[{{\mu }_{0i}}(\pi +1)2\pi r\]

    C)                 \[{{\mu }_{i}}/2\pi r\]                    

    D)  none of the above

    Correct Answer: A

    Solution :

                                             According to the question, the magnetic field due to straight part of the conductor at the centre is given by                                 \[=\frac{{{\mu }_{0}}i}{2\pi r}\] Now the magnetic field due to a circular part of wire at the centre \[=\frac{{{\mu }_{0}}i}{2r}\] These two fields are in opposite direction. Therefore, net field\[=\frac{{{\mu }_{0}}i}{2r}-\frac{{{\mu }_{0}}i}{2\pi r}=\frac{{{\mu }_{0}}i}{2\pi r}(\pi -1)\]


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