Four long, straight parallel wires each and every carry current I. In a plane perpendicular to the wires, the wires are at the corners of square of side length a. Determine the magnitude of the force per unit length on one of the wires for the given: (Use the given as required: I, µ0, and a.)
(i) All the currents are in the similar direction.
(ii) The currents in the wires at adjacent corners are oppositely directed.