A coaxial cable is made of a 0.1-in.-square inner conductor and a 0.5-in.-square outer conductor.
The potential at a point in the cross section of the cable is described by Laplace's equation. Suppose the inner conductor is kept at 0 volts and the outer conductor is kept at 110 volts. Find the potential between the two conductors by placing a grid with horizontal mesh spacing h = 0.1 in. and vertical mesh spacing k = 0.1 in. on the region
D = {(x, y) | 0 ≤ x, y ≤ 0.5}.