A regular polygon of n sides is formed by bending a wire of total length `2pi `r which carries a current i.
(a) Find the magnetic field `B` at the centre of the polygon.
(b) By letting `nrarroo` deduce the expression for the magnetic field at the centre of a circular coil.

Answer

`1`

Explanation

`B=nxx(mu_(0)i2cos alpha)/(4pi1/2tan alpha)=(nmu_(0)icos alpha)/(pil tan alpha)`
`alpha=pi/2-pi/n`
`=(u_(0)"in"^(2)sinpi/ntan pi/n)/(piL)`