[SOLVED] E-field at the center of a semicircle 1. The problem statement, all variables and given/known data Calculate E at center of semicircle: A uniformly charged insulating rod of length L = 12 cm is bent into the shape of a semicircle as shown. The rod has a total charge of Q = -6 nC. Find the magnitude of the electric field at the point P -- the center of the semicircle. (Answer in units of N/C.) 2. Relevant equations E = K((Q)/(r^2)) 3. The attempt at a solution To find the distance/radius from the point P to any point on the semicircle would be... 12cm*2 = circumference 2*pi*r = 24cm r = 3.8197cm or .038197m When I use the equation under the "relevant equations" heading, I'm getting a really huge (E) of about 36,970 N. This can't be right and I'm not sure of where to go from here. Any help would be greatly appreciated. Thanks!