The figure shows four long parallel wires which carry equal

The figure shows four long parallel wires, which carry equal currents into or out of the page as shown. In which configuration, (a) or (b), is the magnetic field greater at the center of the square. Explain your reasoning.

Solution

in case a

as in case b, wires at the opposite corners of square will cancell each other\'s magnetic field

in case a they will add up