A uniformly charged ring of radius 10.0 cm has a total charge of 58.0μC. Find the electric field on the axis of the ring at the following distances from the center of the ring. (Choose the x-axis to point along the axis of the ring.). I know the equation I want to use is E= (kQx)/(x^2+r^2)^(3/2) where x is distance from the center of the ring and r is the radius. But, I don't know where this equation comes from. I know E=kq/r^2, so I'm just not sure where the x/(x^2+r^2)^(3/2) comes from.