We have a uniformly charged sphere (charge is all over, not just on surface) and want to determine the electric field at a point that is distance X from the center of the sphere. The radius of the sphere is known. I first derived the electric field from a disk to a point that is distance x away from the center of the disk. s = surface density = Q/A ep = permitivity of free space constant r = radius of sphere R = radius of disk I found this to be [s/(2ep)]*[1 - x/sqrt(x^2 + R^2)] Now I have to integrate this from X - R to X + R. But I cannot figure out how to express the radius of the disks in terms of the sphere radius without introducing more variables (ie angle variable). I am also confused as to how exactly to correlate surface density with volume density. I wish to use Coulomb's Law and not Gauss'.