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I'm just wondering what the point of polarizing an ungrounded AC power source is.


Ahh.. One side of your single-phase AC power soure *is* grounded at the source, meaning it literally is connected to the dirt outside your house. The other side is the actual AC supply, known as the "hot" or "live" wire. Only one of the two wires is hot.

Originally, electricity used a single wire distribution system in many areas, and each house had their own grounding rod(s) to complete the return loop back to the supplier. But house grounding systems were (and are) often suspect, so now a pair of wires comes in from the utility company: the new wire is the "neutral" wire, which is actually grounded out on the utility company end of things.

But just to continue with the safety trend, we now have three wires, where the hot and neutral are now supplemented by a local earth ground, which is connected to grounding rods at the utility pole and at the house electrical panel -- often just connected to a copper water supply in older homes, or to grounding plates/rods in newer construction.

Cheers