Question

The following arrangement consists of five identical metal plates parallel to each other. Area of each plate is A and separation between the successive plates is d. What is the capacitance between P and Q?

Answer 1

Here, $C_{45}$ is in parallel with $C_{43}$ which is in series with $C_{21}$ and this combination is in parallel with $C_{32}$.
$C_{eq}=\frac{(C+C)C}{(C+C)+C}+C=\frac{2C^2}{3C}+C=\frac{2C}{3}+C=\frac{5C}{3}=\frac{5}{3}\frac{{ϵ}_{0}A}{d}$