A square conducting loop of side length L carries a current I. The magnetic field at the center of the loop is

Magnetic field at the centre due to either armB1=μ04π×I(L/2)sin45°+sin45° =μ04π×22ILB=4B1=4×μ04π×22IL  i.e.,   B∝1LField at centre due to the four arms of the square