Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!think.com!spool2.mu.edu!samsung!uakari.primate.wisc.edu!dali.cs.montana.edu!milton!whit From: whit@milton.u.washington.edu (John Whitmore) Newsgroups: sci.electronics Subject: Re: ANOTHER house wiring question (this one's basic) Summary: Current-carrying wire has voltage drop Message-ID: <14404@milton.u.washington.edu> Date: 15 Jan 91 00:41:07 GMT References: <1948@umriscc.isc.umr.edu> Organization: University of Washington, Seattle Lines: 41 In article <1948@umriscc.isc.umr.edu> robf@mcs213k.cs.umr.edu (Rob Fugina) writes: >In article mrapple@quack.sac.ca.us (Nick Sayer) writes: >>Now ground and neutral clearly are not the same thing. I would >>expect negative side effects were I foolish enough to hook >>a light bulb between hot and ground. One easily seen effect would be the tripping of the GFI (ground- fault interrupter) on that circuit. All kitchens, baths, and outdoor sockets (including sockets in unheated garages) must be GFI-connected nowadays. The GFI looks at the current in the HOT minus NEUTRAL wires, and if the difference is nonzero, it trips just like a breaker would trip during a short circuit. > >Ground and neutral are exactly the same thing. If you were to trace the >wires back to your breaker box, you would find bare wires (ground) and white >wires (neutral) both connected to a grounding strip. Wrong place to look. The appliances take current from HOT and return the current through NEUTRAL to complete the circuit, NEVER putting any current through GROUND except in a sparks-flying fault condition. As a result, the far end (away from the breaker panel) of the NEUTRAL wire will exhibit I*R voltage due to the current drawn (and a cheap Skilsaw can easily top 50 amperes for a few milliseconds in normal starting). The resistance and inductance of the neutral wire will cause some voltage drop (16VAC is not unheard of). Just because ONE end is connected to ground, doesn't mean the wire is grounded! The ground wire has no other connections, barring faults, so connecting one end to ground IS sufficient. > The two wires that come from the pole are both hot, Miscount! Three wires come from the pole: two phases of 120 VAC and neutral. That neutral wire is grounded to the same water pipe and grounding block in your breaker box as the ground and neutral wires connect to. The omission of the neutral wire would require perfect current balance between 120V appliances on the two phases (not likely.) All the houses on the block will typically have ground connections for that neutral wire, so losing one connection might not have immediate consequences, though. I am known for my brilliance, John Whitmore by those who do not know me well.