WBJEE 2020 Physics Solved Paper

As shown in the figure, a single conducting wire is bent to form a loop in the form of a circle of radius ‘r’ concentrically inside a square of side ‘a’, where a : r = 8 : π. A battery B drives a current through the wire. If the battery B and the gap G are of negligible sizes, determine the strength of magnetic field at the common centre O.