Basic Home Electrical Question

[wardellcastles]

I've been reading up on basic home wiring. After I few pages I have one basic question that I need to get a good answer to before I read more.

All my reading refers to the black wire as the "hot" wire and the white wire as the "neutral" wire. Polorized plugs force the black wire on the outlet to connect to the black wire on the appliance.

The reason all this is supposedly done is because current flows from the black wire in the fuse box to the white wire the neutral bus bar in the fuse box.

Now why I may buy this "current flow" for direct current, it seems to run against the concept of alternating current.

Can someone set me straight on this topic? What EXACTLY do the terms "hot" and "neutral" mean?

Thanks

[wardellcastles]

Rich,

Not that I would do this (AND I RECOMMEND NO ONE ELSE DO THIS EITHER), but does that mean that when replacing a switch or an outlet, that I could turn the power back on and touch the NEUTRAL (white) wire and not receive a shock?

Wardell

..panix.com/~richgr/ Asst Owner:Sibernet-L

[wardellcastles]

I think I understand this a little better now thanks to everyone's responses.

Let me restate what I think some people have said plus what else I've managed to google.

If I pretend the electron flow was water instead of electrons, then what's happening is that the electric company is pushing and pulling "water" through the black wires at the rate of 60 cycles per second at an energy level of 120 volts, hence this is "hot".

The white wire, e.g. "pipe" is connected to a large calm lake, e.g. ground potential.

Now If I were to touch the white wire (assuming it was wired correctly to the "calm lake", it's just connected a resevoir of electrons at ground potential so there's no flow. However if I were to touch the black wire and provide a path to ground, then this "water" would be flowing through me, e.g. an electrical shock.

Is this at least a reasonable analofy of why black is "hot" and why white is "neutral"?

Thanks to everyone for their response.

[Robertm]

No, not quite. Single phase oscillates between 169 positive peak and 169 volts negative peak, not 120 Volts. This yields the effective voltage of 120 volts (RMS). RMS voltage is .707 x peak. Peak is 1.414 x RMS.

Bob

[Don Young]

[Toller]

I was confused about this once myself. Do a google search; I am sure you will find some nice diagrams that explain it better than I can. (Hint: the neutral is always 0v, the hot alternates...)

[Rich Greenberg]

The "neutral" wire is at ground potential. The "hot" is (usually)

120vac relative to the neutral. The hot doesn't have to be black, although thats the most commonly used color. White must be the neutral. Green must be the ground. Any other color can be used for the hot. True with A.C. the current flow goes back and fourth. Its the voltage relative to neutral that defines the hot.

[Ralph Mowery]

If the outlet is wired correctly you could touch the Neutral (usually white) while grounded and not get shocked. The Neutral is suspose to be grounded back at the service entrance/panel box.

To answer your question above, the electricity does not actually come out of the black wire and return on the white wire. That is just simple thinking to make it easy to explain the circuit.

In most homes in the US there are 3 wires comming in. There are 2 hot wires and one neutral. There are 240 volts across the two Hot wires and 120 volts from the neutral and either hot wire. If only 240 volt devices are used then there is no need for the neuteral wire. If you start adding 120 volt devices , some on one side and some on the other side then the current will be unbalanced on the hot wires and the neuteral will have some current on it. If you could put the same current load on each side of the two circuits then there would again bo no current flow on the neutral wire and it could be disconnected and the devices would continut to work normally.

[Colbyt]

On a properly wired system that is working properly you are able to touch the bare/green wire or the white wire and not receive any shock. Only the hot wire, usually black has any shock potential.

And please don't try this at home kiddies, as long as you aren't grounded you can handle the hot wire with the juice on. Electricians do it all the time while standing on a fiberglass ladder. You can get a nasty shock changing an outlet live because the ground wire connect to the part of the device you are holding. Please remember that even a 110V circuit can kill you it the right situation.

And for the OP: I am not qualified to explain it to you but the term alternating current refers to what happens before the electricity enters your home. There are two generators working in a 60HZ cycle that feed juice to the line. Somehow this permits more juice to flow farther at a lower cost. That is an extremely simplified explanation. But it is about all I can explain.

Colbyt

[FDR]

As long as there's nothing connected to the circuit that is drawing power. However, if there's current going through the circuit, anwhere on that particular circuit (wires connected to the same breaker) there's going to be some voltage potential because there's a resistance from that white wire back to the breaker box. Now the voltage is most likely low (less than a volt) so unless you are sticking a white wire in your mouth and the ground wire up your ass, the likely hood is nearly zero that you will feel a shock.

The best thing to do is wear rubber bottom sneakers and synthetic gloves if you plan on working on a powered circuit and you are a novice.

[Brad Bruce]

"FDR" wrote in news:BcB6f.1287$ [e-mail]:

If you're a novice (or anything less than a pro...) TURN OFF THE POWER!!!

Brad

[Toller]

Heck, my wife (and millions of others) does it several times a day. The chassis of our stove and dryer are connected to the neutral. Unless the neutral connection has come loose, it is an almost infinitely better ground than the person touching it; so the toucher gets close to 0v.

In the situation you describe is even safer; a (presumably open) switch or a unused outlet, you could lick the neutral and get nothing; unless the ground bus has come loose, it is absolutely 0v.

[Jeff]

Yes it may be somewhat confusing. As Einstein (100 years ago last month) said, it's all relative. Try to picture an oscillating wave representing

120VAC. The difference between the top and bottom of the waves is 120 V. Now if we force one side to be grounded the other side must be oscillating between plus 120 V and minus 120 V. But remember there never is more than 120 V relative to ground.

On Navy ships all 120 VAC power has no neutral. Each leg is hot and is 60 VAC relative to ground similar to the way 240 VAC in your house is set up. This is for safety since you will only get a 60 V shock between a hot and ground. We always had to check out test gear we took ships to make sure that the neutral was not connected to ground.

If you really want to be confused try to understand 3 phase power. Ever notice how all high voltage lines are in sets of three. With three phase power the sum of the power supplied to a load is constant so motors and generators run much more smoothly.

[Toller]

The first time I tightened the connections on my main breaker I did exactly that, while holding an insulated allen wrench. I knew it was silly, but it was the MAIN BREAKER.

[Edwin Pawlowski]

3 Phase is really easy to explain. You put a volt meter across any two wires and you get 277 volts. but across the three is 480. Simple math huh? Then there is power factor . . . . . .

[Ralph Mowery]

Any two will get you 480 volts. If wired in the Y configuration and the center is grounded , then you get 277 to ground from any wire.

[Edwin Pawlowski]

Oops, that's right of course. 2 x 277 = 480

[FDR]

Then there's the whole Y or Delta configuration. Hated those classes in college.

[Beachcomber]

I think you might be confused with the terms AC and DC, current flow and electron flow.

In a DC circuit, current flow was described as flowing from the (+) terminal to the minus terminal (-). This convention existed since the days of Ben Franklin. However, electrons flow from the (-) terminal to the (+) terminal (the opposite direction to current flow). Electricians and circuit designers are interested in current flow. Electron flow might be of interest to a scientist.

In an AC circuit, the poles are changing 50 or 60 times a second. This has no effect on the magnitude of the current flow. The electron flow (unlike a DC circuit) will effectively be zero, but the AC current flow could be huge. Usually (just for convention) we say the current is flowing from the hot wire and back through the neutral, but this is just a concept, it actually does not have a direction.

Beachcomber

[RBM]

Now If I were to touch the white wire (assuming it was wired correctly to the "calm lake", it's just connected a resevoir of electrons at ground potential so there's no flow. However if I were to touch the black wire and provide a path to ground, then this "water" would be flowing through me, e.g. an electrical shock.

Not exactly, when the white wire or neutral is part of a circuit, there is "flow", and if you were to cut that neutral wire and get between the two wires, or the live end and ground, there will be flow through you.