Working on a system to collect solar energy, you are trying to move some charged particles through the open interior of a uniformly charged ring. A colleague vaguely remembers Newton's and Priestley's argument that no electrostatic force is exerted on a charged particle inside a uniformly charged sphere. He suggests that the same must be true for a charged ring, and so you can send the charged particles through any part of the ring interior without the particles feeling an electric force and being deflected by it. You are skeptical, wondering if there might at least be a restriction on the path over which you send the particles such that they experience no electric force.