In the following figure,a wire bent in the form of a regular polygon of $n$ sides is inscribed in a circle of radius $a$. The net magnetic field at the centre will be

  • A
    $\frac{{{\mu _0}i}}{{2\pi a}}\tan \frac{\pi }{n}$
  • B
    $\frac{{{\mu _0}ni}}{{2\pi a}}\tan \frac{\pi }{n}$
  • C
    $\frac{2}{\pi }\frac{{ni}}{a}{\mu _0}\tan \frac{\pi }{n}$
  • D
    $\frac{{ni}}{{2a}}{\mu _0}\tan \frac{\pi }{n}$

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