1. The problem statement, all variables and given/known data Find the potential at a distance from a very long line of charge with linear charge density (charge per unit length) λ. I actually have this solved with the help of my book, but I need an explanation of the results. V = (λ/2πε)ln(rb/ra) Where the electric potential at rb is zero. 2. Relevant equations ΔV = -∫E⋅ds 3. The attempt at a solution V = (λ/2πε)ln(rb/ra) From this equation, it is clear that if you can't set the electric potential at the line of charge to be zero, otherwise you would have ln(0). Additionally, if it is zero at rb you get ln(infinity) = infinity. So does that mean it is not possible to find the electric potential with respect to the line of charge or infinity? I'm not sure how I would solve a problem like this on an exam if electric potential is relative, and rb is some arbitrary finite point. Wouldn't different points for rb yield different results for the electric potential?