I've been reading through this explanation where the author goes through the natural progression of why a three-prong AC outlet was made (Why Three Prongs?) , but I have some trouble imagining how earth ground plays a role here.
First off, for just a two prong AC system, which I take it to mean a floating source system, one can't be shocked from touching just one of the two "hot" wires, but only by holding both at the same time and acting as the short circuit between them (does voltage just drop to the value of the wire with the lower potential here, while current spikes?). Just touching one of the hot wires is analogous to only hooking a single wire to one terminal of a battery I imagine--there's no return path for current to start flowing. Even if one were barefoot and standing on a damp floor, with no grounding wire in the system at this point, no danger of shock exists.
So reading further down the link now, how does the fact that the neutral wire (which is grounded) exists allow the hot wire current to go through a person standing on earth ground? The author mentions that by grounding one half of the system, they essentially connected one half of the system under the persons feet. Where specifically is current flowing in the ground to create this loop or return path for current? Is it reaching wiring underground to complete the connection?
To try to drive this idea home, what happens to a power supply when both sides of the circuit are connected to earth ground? How does this make a short circuit between the two sides of the circuit? I thought earth ground was a sort of "reservoir" of sorts that is unaffected by current moving into it.
Any help explaining this concept is greatly appreciated.