PHYS102: Introduction to Electromagnetism

Watch this lecture, which leads us from the parallel-plate configuration back to the point-like charges that we started with when introducing Coulomb's Law. The reason we discussed the potential for the seemingly more complicated situation of densely crowded charges on parallel plates before going back to the individual point charge is math. We found that the potential between two plates changes in direct proportion to the distance from one of the plates. This is connected to the fact that the electric field lines between the plates are parallel straight lines.

For a point charge, recall that the field lines form a radial star shape. As a consequence, the potential in this situation is more difficult to compute. Fortunately, the result is relatively simple, differing only slightly from Coulomb's formula for the electric force of a point charge. The main difference is that the potential decreases with the inverse distance to the point charge, not with the inverse squared distance.