Which of the following best explains why the electric field at the outer surface of a charged solid conductor in electrostatic equilibrium must be perpendicular to that surface?
a) Like charges on the surface spread out until they are as far apart as possible, so only a component pointing straight outward can remain
b) Gauss’s law requires the electric flux through a small surface patch to vanish unless the field is normal, so any tangential component must be zero
c) Any tangential component of the electric field would exert a force along the surface and move charges, so equilibrium allows only a perpendicular component
d) Because the conductor’s surface is an equipotential, the electric field must lie along the surface, making it parallel rather than perpendicular