The capacitor stores juice in a magnetic field, it can provide stability I understand (but can be wrong here) so only for DC. For AC it's funny but again how I remember it was there is a neutral and a hot something to do with one wire on the windings the other on the housing or magnetic (feel free to correct me) the 'ground' third plug is to cases and whatever can provide an easier ground than hurting the equipment or people and pets, children with forks and a curiosity. Goes to the outside of the electrical box and there it's kindof optional in theory to a copper rod 11feet in The ground or something. The volts are looking for the easiest was to each other more of a gradient or doffence more push or drive to do so, it feels it's polar opposite via the megnetic field, you are conductive and it might find between your left and right hand the way to go, not the wood to burn or metal to arc out on. (Stories are involved here but leaving those put) one thing that always bothers me is irrational fear. Respecting safety and understanding is good, but respecting common sense and being aware is normally enough. Have one hand in your pocket and standing on something insulated and having the item you are on insulated and no distractions should be enough, not posting pics of it is my civic responsibility). I have a clip on one side and an insulated voltmeter probe on the other, no exposed wires. I'd like to show it off next week if anyone wants to see.