Two identical long wires denoted A and B in Fig. are part of the electric circuit shown in the figure and therefore carry some currents. The wires are characterized by resistance per unit length, R0, have length L each and are spaced by distance a. What is the magnitude F of the force the wires exert on each other? Is it the force of attraction or repulsion? For the given resistance R of the external resistor, what should be the length L to achieve maximum possible F? What is that maximal Fmax?
