1. The problem statement, all variables and given/known data A rod is bent into a semi circle of 180 degrees. The bottom half has a charge of -q and the top half a charge of q. Find the electric field at the center of the circle, point P. 2. Relevant equations E = kq/r^2 3. The attempt at a solution I tried to set up an integral for this. I know that the horizontal components will cancel out, and the vertical will be additive, pointing in the negative y direction. S = integral 0 - 180 S((2kq/r^2)sin(theta))d(theta), which is (2kq/r^2)(-2) 4kq/r^2 which seems wrong. Any help?