Two long, parallel wires of length L, separation d, and cross sectional radius a are connected by

Question:

Two long, parallel wires of length L, separation d, and cross sectional radius a are connected by a U-turn at each end to form a closed circuit. Insert a battery with potential difference V at one U-turn and a shunt resistor R at the other U-term. Assume that R is much larger than the ohmic resistance of the wires and the internal resistance of the battery. Show that the wires repel (attract) if R is smaller (greater) than