Questions: Conductors in Electrostatic Equilibrium
2 questions to test your understanding
Score: 0 / 2
Question 1 Short Answer
A conducting sphere carries total charge +Q. Where does this charge reside, and why?
Think about your answer, then reveal below.
Model answer: All charge resides on the outer surface. If any charge were in the interior, a Gaussian surface drawn just inside the conductor would enclose net charge, implying nonzero flux and therefore nonzero interior field — which would contradict equilibrium, since free charges would then continue to move.
The key chain of reasoning is: equilibrium → E_interior = 0 → zero flux through any internal Gaussian surface → zero enclosed charge → charge must be on surface. This argument holds for any shape of conductor, not just spheres.
Question 2 Short Answer
The electric field at the surface of a conductor is perpendicular to the surface. What would happen if there were a tangential component?
Think about your answer, then reveal below.
Model answer: A tangential field would exert a force on surface charges parallel to the surface, causing them to flow along the surface. This current would continue until the tangential component vanished — so a tangential field is impossible in equilibrium.
This is a dynamic stability argument, not just a static rule. The conductor 'enforces' the perpendicularity condition by moving charges whenever it is violated. The steady-state result is that the surface is an equipotential and the external field is purely normal.