Two thin rods of length l carry equal charges Q uniformly distributed over their lengths. The rods are aligned, and their nearest ends are separated by a distance x (see the figure below). Calculate the mutual electric potential energy, that is, ignore the energy required to put the charges on the rods in the first place.

Two thin rods of length l carry equal charges Q uniformly distributed over their lengths. The rods are aligned, and their nearest ends are separated by a distance x (see the figure below). Calculate the mutual electric potential energy, that is, ignore the energy required to put the charges on the rods in the first place.