Question: A circular ring of wire of radius r0 lies in a plane perpendicular to the x-axis and is centered at the origin. The ring has a positive electric charge spread uniformly over it. The electric field in the x-direction, E, at the point x on the axis is given by
E = kx/(x2 + r02)3/2 for k > 0
At what point on the x-axis is the field greatest? Least?