Teller's theorem

Teller's theorem, in electromagnetism, states that a charged conductor in electrostatic equilibrium must be an equipotential surface, meaning its entire surface has the same electric potential. This occurs because free electrons in the conductor move until they balance out any internal electric fields, resulting in a uniform potential. Additionally, the electric field just outside the surface is always perpendicular to it, preventing charges from moving along the surface. Essentially, the theorem explains why conductors in electrostatic balance have no internal electric fields and uniform surface potential, ensuring stable charge distribution.