Figure shows a square loop made from a uniform
wire. Find the magnetic field at the centre of the square
if a battery is connected between the points A and C.

Explanation

Solution: The current will be equally divided at A. The fields
at the centre due to the currents in the wires AB and DC
will be equal in magnitude and opposite in direction. The
resultant of these two fields will be zero. Similarly, the
resultant of the fields due to the wires AD and BC will be
zero. Hence, the net field at the centre will be zero.