1. The problem statement, all variables and given/known data Find the capacitance of an isolated ball-shaped conductor of radius R1 sorrounded by an adjacent concentric layer of dielectric with permitivity ε and outside radius R2. 2. Relevant equations 3. The attempt at a solution The official solution says something like: Difference of potentials is --- int(R1,R2)(E*dr) + int(R2,∞)(E*dr) Sorry, but I don't know how to write equations nicely. I dont quite understand what is the second integral here for. Can someone explain?