A simple model of electric ground and of a dc power supply

Carl E. Mungan

U.S. Naval Academy

In a direct-current (dc) circuit, a power supply and a ground can each be modeled as a large, distant, conducting sphere bearing a net surface charge. The relation between the charge on and potential of each of these spheres is analyzed before and after they are connected to a concentric spherical capacitor that is initially uncharged. Expressions for the potential at all points in the vicinity of the charged capacitor (both inside and outside it) are written down.