RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    An infinitely long straight conductor is bent into the shape as shown in figure. It carries a current (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 \[=\frac{{{\mu }_{0}}i}{2r}-\frac{{{u}_{0}}i}{2\pi r}\] \[=\frac{{{\mu }_{0}}i}{2r}(\pi -1)\]


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