A solid chunk of metal carries a net positive charge and is also polarized by other charges that are not on the metal, as shown in Figure 22.110. The electric field very near the surface of a metal in...

A solid chunk of metal carries a net positive charge and is also polarized by other charges that are not on the metal, as

shown in Figure 22.110. The electric field very near the surface of a metal in equilibrium is perpendicular to the surface:

any component of the electric field parallel to the surface would drive currents in the metal. (Along a rectangular path, part

inside and part outside the metal, the round-trip potential difference is zero, so the parallel component of electric field is the

same just inside and just outside the surface.) Let S be the “local” surface charge density—the surface charge per unit area

(C/m2) at a particular location on the surface.