1. The problem statement, all variables and given/known data Two infinitely long lines of uniform charge λ lay parallel on the xy plane (0, ±a) What is max E field in the xz plane. No values are given. Symbolic answer is expected. 2. Relevant equations equation for an infinite line of charge E = λ / ( 2 π ε0 r) 3. The attempt at a solution My first thought is max E field would be at a point that would be formed by an equilateral triangle. At this point we would have a radius of 2a and the following E = 2λ / (4 π ε0) = λ/ (2 π ε0 a) (all in +z direction) I then think that to maximize E field I need to minimize r. So what if I observe at a distance where r approaches 0. At this point I am on the surface of one of the lines. If r = 0 the equation falls apart due to div by 0. If I take the limit as x→0 it goes undefined. If I say r=1 that's great, but 0.5 is better, and 0.005 is even better yet. I understand that I will have some field due to the other wire to figure in with my magnitude but if I am very very close to one of the lines of charge I think this will be insignificant. Am I conceptualizing this properly? Is there an equation for E field where r = 0?