DISTRIBUTION OF CHARGES IN A CONDUCTOR AND ACTION AT POINTS

The unit's final section brings together several earlier results -- that a conductor's whole surface sits at one uniform potential, that a conductor's free charge resides entirely on its surface, and that the field just outside a charged conductor is E = sigma/epsilon0 -- to explain how charge actually distributes itself, non-uniformly, over the surface of a conductor whose shape is not a simple sphere. This leads to the phenomenon of action at points (corona discharge) at sharp conductor edges, its practical use in the lightning arrester (lightning conductor) that protects tall buildings, and finally to the Van de Graaff generator, a machine specifically engineered to build up extremely high electrostatic potentials of …