1. The problem statement, all variables and given/known data Here's the problem: 2. Relevant equations V = ke ∫ dq/r V is the electric potential, ke Coulomb's constant, q the charge and d the distance. λ = q / L , where λ is the charge density, q the charge and L the length of the rod. 3. The attempt at a solution I have one solution for the problem. What I want to know is why is my answer incorrect. Since electric potential is a scalar and not a potential what I calculated was the electric potential produced by the left part of the rod, from 0 to L/2, and multiplied the resulted for two due to the symmetry of the problem (I thought that the electric potential produced by the rod from L/2 to L was the same as from 0 to L/2) q = λ*L ⇔ dq = λ*dx ⇔ dq = α*x*dx V = 2*ke*α ∫0L/2 x/sqrt(x²+b²) dx I solved the integral and got: V = 2*α*ke*[ sqrt( (L/2)² + b² ) - b ] It is incorrect tho. Any help will be appreciated! Thanks in advance.