Final answer:
The electrostatic potential energy of a configuration of charges is positive when charges have the same sign and negative when the charges have opposite signs, indicating the work done against or aided by the electrostatic force.
Step-by-step explanation:
The electrostatic potential energy (Utot) of a configuration of charges is positive if the charges are of the same sign and negative if the charges are of opposite signs. This potential energy represents the work necessary to bring these charges together from an infinite separation without any acceleration. The positive or negative sign of the electrostatic potential energy indicates whether the work done is against the electrostatic force (positive Utot) or aided by it (negative Utot).
A system of two like charges, such as two positive charges, would exhibit repulsive forces, requiring work to be done to bring them closer, resulting in positive potential energy. Conversely, a system with charges of opposite signs would attract each other, and bringing them closer would release energy, resulting in negative potential energy. When calculating the total potential energy of a system of charges, the individual interactions are considered, and the potential energy is summed accordingly.