1. The problem statement, all variables and given/known data You have two concentric cylinders. The inner cylinder has radius a and the external cylinder has radius b. Find the electric potential in the region between the cylinders. [Hint: The final equation takes the form V(r) = constant1 - constant2 ln(something) ] 2. Relevant equations I think: Gauss's law: [itex]\Phi[/itex]=EA=q/ε Coulomb's law: E=q/(4πεr^2) 3. The attempt at a solution I really don't know.