Take a ring of charge and stand on its axis. Every piece of the ring pulls you sideways as well as along the axis — but for every piece pulling you one way, there is a piece directly opposite pulling you the other way. Those sideways parts cancel exactly. Only the axial parts survive, and that is why the answer comes out so clean.
Choose a positive or negative ring. Step through five stages with the arrows. Drag the point P along the axis to move closer or further from the ring. Switch the camera between 3D, front, side and top views.
Step two takes one small piece of the ring and splits its field into a part along the axis and a part perpendicular to it. Step three adds the piece directly opposite, so you can watch the perpendicular parts cancel. Step four adds everything and leaves only the resultant. Step five marks the two special points: the field is exactly zero at the centre, and strongest at a distance of R divided by root two. The panel shows how far along the axis you are and how strong the field is.
The ring radius is fixed at 2 and cannot be changed. Field values are normalised — k and Q are both taken as 1.
You should be able to say why the field is zero at the centre of the ring, even though every part of the ring is charged.