1. The problem statement, all variables and given/known data Calculating the horizontal component of an electric field at the origin of a semi circle. The image link is: http://imgur.com/SXYs4Rp 3. The attempt at a solution I've tried using the formula k∏(Q)/r (8.98755*10^9)∏(-7.85*10^-6) / .113 = -1.961 * 10^6. Can anyone see what I am doing wrong?