Find an expression for the magnetic field induction at the centre of a coil bent in the form of a square of side `2a`, carrying current I, figure

Explanation

Here, `phi_1=45^@, phi_2=45^@`
Total magnetic field induction at O due to current through all the sides of a square is four times that due to current through on arm of the square and is given by
`B=4xx(mu_0)/(4pi)I/a(sin45^@+sin45^@)=4xx(mu_0)/(4pi)I/a(1/sqrt2+1/sqrt2)=(sqrt2mu_0I)/(pia)`