- #106
sophiecentaur
Science Advisor
Gold Member
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Evil Bunny said:Most houses (if not all) in the US are wired with single phase. Yes, it originates as three phase (upstream) but we're only using one of the phases. This third prong on the plug receptacles that people are calling the "ground wire" (whose technical term is an "equipment grounding conductor") has absolutely nothing to do with the neutral whatsoever. It is used for bonding the metal parts in your house.
I know that you're only using one of the phases but other users are using the other two phases and the neutral is common to all users and the system has to work as a whole. This neutral conductor is sure to be near Earth potential, for symmetry reasons. If you look at massive electrical distribution lines there is one tiny 'fourth conductor' which is strung from pylon to pylon.
As you say, the reason for a local ground / Earth is to give you something to hang all exposed metal onto. This means that you can never get many volts between yourself, your feet and anything you are likely to touch as long as you are not actually poking about inside some equipment.