The electrostatic field must be zero inside a conducting body. A non-zero field would act on mobile charges in the body and so produce currents that would cause the charge distribution to change with ...The electrostatic field must be zero inside a conducting body. A non-zero field would act on mobile charges in the body and so produce currents that would cause the charge distribution to change with time. Since the electrostatic field is zero everywhere inside a conducting body, it follows from that the electric field just outside a conducting body can have no components parallel with the surface.
