Lawrence R. Mead computed the resistance of square lamina with “point contacts” at two opposite corners.1 To this end, he used an infinite number of image charges. The use of image charges to meet boundary conditions is a common method in electrostatics. However, the problem to be solved is not an electrostatics problem as it involves resistance and thus current (i.e., nonstatic charge).
The potential around a current source or sink in a lamina is not the same as that around an electrostatic charge. To derive the potential around a current source, we consider a single current source at the origin of the coordinate system in a lamina extending to infinity. The current will flow in all directions, leading to circular equipotential lines around the source. The sum of all current sources minus the sum of all current sinks within a certain region gives the net flow out of...
