Final answer:
The question pertains to the electric potential energy between point charges in Physics, where the potential energy is zero when the charges are infinitely apart and given by the formula U = kq1q2/r when at a distance r apart.
Step-by-step explanation:
The subject in question is Physics, specifically focusing on the concept of electric potential energy between point charges. When two charges q1 and q2 are infinitely far apart, their potential energy is taken to be zero. This is analogous to considering the ground as having zero potential energy in a gravitational field. Bringing charge q2 from infinity to a distance r from a stationary charge q1 involves doing work against the electric field exerted by q1. The electric potential energy (U) of a two-charge system consisting of point charges q1 and q2 separated by a distance r is given by the equation U = kq1q2/r, where k is the Coulomb's constant.
The potential energy equation is symmetrical with respect to the two charges, meaning it represents the system's potential energy rather than that of an individual charge. This concept also extends to calculating the electric field and the forces between multiple charges in space. For example, the electric field midway between two charges of opposite signs can be calculated using the superposition principle. Meanwhile, the force on a charge in this electric field can be found using Coulomb's law.