1. The problem statement, all variables and given/known data. Trying to find the potential between a variable capacitor that is made up of two coaxial cylinders of radii a and b, with (b-a) << a, when inner cylinder displaced by a distance y along axis. 2. Relevant equations E = λ / 2piε0r V = λ/2piε0 * ln(b/a) when there is no displacement 3. The attempt at a solution I already calculated the potential when there is no displacement by ∫E dr with respect to a and b. But Honestly I don't even know where to start for finding the potential when the inner cylinder is displaced a distance y along the axis. Any help would be appreciated, thanks!