Hi everyone. I have quite a basic doubt, and I thought you could help me. Consider the figure: The cylinders S1 is held at a constant potential, and the same applies for the ring identified by S0. All the surroundings are filled with an insulator material. I want to calculate che capacitance between these two metallic "plates". I order to do this, I want to exploit an already known result; it consists of the solution of the following 2-D capacitive coupling (that assumes symmetry along the axis orthogonal to the page): The approach for the original problem is solving Laplace equation, computing the Electric Field component orthogonal to S0 and deriving superficial charge density. Then integrating all over S0 to compute the total charge. I have in mind the 3d geometry exhibits cylindrical symmetry, so Laplace equation in cylindrical coordinates is equivalent to the one in polar coordinates solved in one slice, which corresponds to the 2d problem in the second figure. Can I proceed like this and then integrating along the angle? Thank you.