A parallel-plate capacitor consists of two flat metal plates of area A separated by a small distance d. The plates are given equal and opposite net charges ± q.
(a) Sketch the field lines and use your sketch to explain why almost all of the charge is on the inner surfaces of the plates.
(b) Use Gauss's law to show that the electric field between the plates and away from the edges is E = q/(ϵ0A) = σ/ϵ0.
(c) Does this agree with or contradict the result of Problem 70? Explain.
(d) Use the principle of superposition and the result of Problem 69 to arrive at this same answer.