how can the black wire be hot and the white wire not be hot if the electricity alternates back and forth from the black wire through my stuff and back over the white wire, if its not going back over the white wire then why have a white wire?
dont be mean when you answer
C

Hi Cindy;

white wires can be 'hot' in a switch loop, is that what you are refering to??

p.s.- most of us have had our rabbies shots !

ummmm, no actually this is a more basic question, my dumb meter is pegged on really really... ummmm, empty
i think i'm asking what is the difference between the white and black, i guess.
like why can i touch a white wire and not get shocked, assuming i can, i'm not going to try though
it just seems like you would get shocked by touching either the W or B wire if the switch is turned on to something and the electricity is going through both of them. know what i mean? seems like they would both have the same ouch factor, i think you call it potential maybe
C

Cindy,
In a 120V circuit, say to an outlet in your livingroom, you have a black, white and a bare or green wire connected to the outlet. The black wire is always "hot" as long as the circuit is turned on. You would always be shocked if you touched the exposed copper of the black wire whether you had anything plugged into the outlet or not. The white wire is the grounded conductor. As long as there wasn't anything plugged into the outlet, or any other outlet on this particular circuit, you could touch the exposed copper of the white wire and not be shocked. But, if there was something plugged into this circuit, using electricity such as a fan, you would be shocked by touching the exposed copper of the white wire.
Why?
Because when an appliance plugged into an outlet uses electricity, the electricity "flows" through the appliance making it work and has to return to it's source. Think of it as a water wheel on an old mill. When the water flows over the mill's wheel it makes the wheel turn and the excess water flows back into the river. When they stop the water from flowing the wheel stops moving and there isn't any water returning to the river. The water is still there, it has just been stopped from flowing over the wheel.

>why can i touch a white wire and not get shocked,
You could. But it is not usually likely because usually by a margin of 9999:1 the copper is a better conductor than you, so too little current travels through you for you to be able to feel it, i.e., <1 mA.

Hey, often one can touch a hot conductor and not get shocked, you know, like when standing on dry nylon carpet.

>it just seems like you would get shocked by touching either the W or B wire if the switch is turned on to something and the electricity is going through both of them.

That is somewhat true.

But juice on the black side is available in a large quantity. Juice on the white side is curtailed by the load and has a clear path to get back to the transformer already.

>seems like they would both have the same ouch factor
If you disconnect the neutral from the bus bar in the panel, that is pretty close to correct - at least as far as killing a human goes.

In the switch loop sparky mentioned, white is an ungrounded conductor, is on the line side (ahead of the load), and is actually an extension of black from the source at the fixture junction box, and in new installations should be marked to indicate that it is ungrounded.

sounds pretty simple i guess, so is that all there is to it? must be more. like why do you get sparks when the B and W wires touch each other accidently? seems to me like the waterwheel idea would mean that the water would just like to keep going down the river. you said the hot wire juice is hotter or there is more of it than in the white wire because some[?] of the electricity is used in the load. and you said that it is going back to a transformer. does the transformer not want to get all of it back or something like that? in any case, it sounds like the white wire is also hot when the fan or whatever is running, maybe just not as hot as the black, maybe, is that right?

Cindy,

Hey, I think you asked a good question!

Fred and the other posters have explained it nicely, and here's another way to look at it.

When the appliance or other load is "on", there's just as much electrical current flowing through the neutral as is flowing through the hot. What's different is the "pressure" or voltage behind the current. There's less "push" or voltage on the neutral side of the load because the load has used that energy to do whatever it does. Keep in mind that it's the current that's dangerous.

There are certain situations where you are more likely to get shocked if you touch the neutral. One is if there is a poor connection in the neutral anywhere between where you might contact the neutral and the common grounding point in the panel (the "ground bus"). A poor connection makes the neutral conductor a fairly poor pathway for the current to return to ground, and so YOU become a more "appealing" path for the current to flow on, back to earth potential.

This situation is made worse if you happen to be in contact with the neutral and standing on concrete (which is in turn in contact with the earth), or touching a water pipe or the like. It's even worse if you're barefoot, and you're wet or sweating. These things all make you a much better conductor of electricity.

Keep in mind that it takes VERY LITTLE current to interfere with the electrical signals that make your heart beat normally. For most people, 6 milliamps can cause electrocution. That's why GFIs (or GFCIs to be more exact) will open the circuit if there's 6 mA of current leaking to ground (not returning on the neutral wire) for more than a few seconds.

BE careful out there!

> why do you get sparks when the B and W wires touch each other...?
Because electric wants to travel from black to white. Black is the top half of the hill. White is the bottom half. We put loads in the middle.

>you said the hot wire juice is hotter or there is more of it than in the white wire because some[?] of the electricity is used in the load. and you said that it is going back to a transformer.
Correct. When the black wire comes from the transformer, that is the top of the hill. When the white wire returns to the transformer, that is the bottom of the hill.

>does the transformer not want to get all of it back or something like that?
If it were sentient, it would want it all back desperately. Actually, the electric power has been pushed out on the black side. It wants to get back in, but the white side is the only way back in.

>it sounds like the white wire is also hot when the fan or whatever is running, maybe just not as hot as the black, maybe, is that right?
Kind of. The white wire has current flowing in it. The white wire is its best hope for getting back to the transformer where it wants to be. If you touch it, and you offer it a path, it will take it. But a human is a lousy path compared to the white wire which is a metallic path straight back to the transformer.

Now when you touch the black wire, it's a different story. There is more current available there than can get by via the light bulb or whatever because the light bulb offers resistance and limits how much current can flow. So there is current available on the black wire waiting for any possible means to get back to the transformer.

If you touch the black wire, as much current as can travel through you will do so limited only by the amount of resistance you offer.
(On the white side, you are competing with a copper wire. And the copper wire has a better bid than you by a thousand times over - so it gets the bulk of the current. But if you cut the white wire, you can be the winning bidder.)


[This message has been edited by Dspark (edited 06-23-2001).]

>if the electricity alternates back and forth from the black wire through my stuff and back over the white wire
The white side is there passively (we call it neutral).

The black side is doing the pushing and pulling. So while it is true that the current alternates, power is coming from the black side only. (It's not like the black side pushes then the white side pushes it back.)

so if i use the water analogy some more here, you are calling the electrical pressure voltage like the water pressure in a hose maybe, but its still water, or current, or electricity, you are just describing it in different terms, maybe?
and after the hose is turned on and runs the sprinkler or whatever then just less of the water, or voltage and current, is left to deal with maybe? the water pressure stays at 40# like the voltage stays at 120 volts. you can feel the 40# and the actual effect of the cold water, so maybe the temperature effect of water is like the current effect of electricity, they both are in conduits, ones solid, ones liquid, they both have pressure behind them, then we want to use the effect of the pressure somehow..... maybe the water thing is getting crazy here whatever, just one more thing that i wanta know is if the 120 volts in the black wire just goes straight through the fan or something to the white wire trying to go back to the ground then would a circuit breaker trip in the garage? so does that mean that the white wire is never supposed to be able to let that much current or voltage go back to the ground or transformer or ground bus you referred to? after reading what everyone said, it sounds like the white wire has current whenever something is turned on, but not as much as the black wire because some is used by the fan or load but it looks like they're always the same size wire, seems like the white could be smaller. sorry, too many questions, but this is kinda interesting.
C

> why do you get sparks when the B and W wires touch each other...?
Because electric wants to travel from black to white. Black is the top half of the hill. White is the bottom half. We put loads in the middle.

so this is the wave form or sine wave thing? just looks like a hill on top of the line and an inverted hill under the line? if thats right then it appears that the white wire could have as much current on it as the black wire? in fact if this is the picture i have in my mind, then it looks like the 2 hills are always the same size??
how do you make bold type as a reply to my message?

>so this is the wave form or sine wave thing?
Sorry, no. The wave form has next to nothing to do with this. Please disregard any such inference.


>how do you make bold type as a reply to my message?
It's tough to explain. But there are bracket-boxes with B and /B in them around the bold text. Click on the edit icon (the one with the pencil) for my message and you can see how I put in the UBB codes. You can see how people put in faces too this way.


[This message has been edited by Dspark (edited 06-23-2001).]

>so if i use the water analogy some more here, you are calling the electrical pressure voltage like the water pressure in a hose maybe, but its still water, or current, or electricity, you are just describing it in different terms, maybe?
Yeah!

>after the hose is turned on and runs the sprinkler or whatever then just less of the water, or voltage ..., is left to deal with maybe?
Yeah, no water (current) is lost. It wants to get back to the ground.

>if the 120 volts in the black wire just goes straight through the fan or something
It doesn't exactly. The fan prevents much from flowing and it extracts power from the current.

>so does that mean that the white wire is never supposed to be able to let that much current or voltage go back to the ground or transformer or ground bus you referred to?
It's the device (fan, light, etc.) that impedes the path of the electricity. If you cross black with white with nothing in between, it will trip the CB.

>it sounds like the white wire has current whenever something is turned on,
Right.

>but not as much as the black wire
Same amount, exactly - just most of the power has been extracted.

Perhaps you would find a website on the topic to be interesting?
http://www.howstuffworks.com/power.htm
http://www.epelectric.com/apogee/foe_html/home.htm


[This message has been edited by Dspark (edited 06-23-2001).]

>it sounds like the white wire is also hot when the fan or whatever is running, maybe just not as hot as the black, maybe, is that right?
Kind of. The white wire has current flowing in it. The white wire is its best hope for getting back to the transformer where it wants to be. If you touch it, and you offer it a path, it will take it. But a human is a lousy path compared to the white wire which is a metallic path straight back to the transformer.

Now when you touch the black wire, it's a different story. There is more current available there than can get by via the light bulb or whatever because the light bulb offers resistance and limits how much current can flow. So there is current available on the black wire waiting for any possible means to get back to the transformer.

If you touch the black wire, as much current as can travel through you will do so limited only by the amount of resistance you offer.
(On the white side, you are competing with a copper wire

OOOOOOOOOOOOhhhhhhhhhhhhhhhhhh
duhhhh, i get it, the black wire is just the stored energy like a balloon blown up or water in a hose or a suspended weight, waiting for a way to release all of that pent up energy by getting to the transformer, and the white wire is made to be a very easy way to get there as opposed to going through me with more resistance then back into the white wire to the transformer. sorry i'm picking this up sorta slow, but the wave hill thing is not working for me too well yet. the sine wave is just a representation of the presence of current or voltage? if the top is hot and the bottom is neutral compared to the hot where the hot side is being pushed and the neutral side is being pulled then it doesnt seem like it would ever change whether there was a fan load or not in the middle. maybe i have this pictured wrong. it just seems like what goes out and back on these wires would balance out and look the same with the equal amounts on top and below, going and coming.
i talk too much so dont worry about replying if i'm too far out in left field thanks

one other thing though, sorry
>if the electricity alternates back and forth from the black wire through my stuff and back over the white wire
The white side is there passively (we call it neutral).
The black side is doing the pushing and pulling. So while it is true that the current alternates, power is coming from the black side only. (It's not like the black side pushes then the white side pushes it back.)
so this means like i said, i hope, that the black wire current still travels on the white wire because it wants to go back to the transformer that way, but its not like its really going that one direction from the black to the white, because you said that it alternates, as in a.c. alternating current. so i keep coming up with this dumb question about how come there could be more current on the black wire when it is alternating back and forth from the source through the black wire and load and white wire and to the transformer which is where it came from to begin with i assume. some how it seems that it should be equal on both the white and black since it alternates, but i remember making sense of a comment i made a little while ago that it made sense that there was more current on the black wire because after going through the fan there wasnt as much current remaining to come out on the white wire. one of me is wrong

WOW! that was a book, opps

just took a breath and reread some things:

When the appliance or other load is "on", there's just as much electrical current flowing through the neutral as is flowing through the hot. What's different is the "pressure" or voltage behind the current. There's less "push" or voltage on the neutral side of the load because the load has used that energy to do whatever it does.

to summarize:
1. Forget what i said about the wave thing, i misunderstood.
2. The current IS the same on the hot and neutral for the fan.
3. The voltage pressure is less on the neutral side of the fan.

[This message has been edited by Cindy (edited 06-23-2001).]

>i get it, the black wire is just the stored energy like a balloon blown up or water in a hose or a suspended weight, waiting for a way to release all of that pent up energy by getting to the back to transformer, and the white wire is made to be a very easy way to get there as opposed to going through me with more resistance then back into the white wire to the transformer.
You probably get it. But that energy is released all along the trip. Most of it is consumed the the load (light, fan, motor, etc.).


>but the wave hill thing is not working for me too well yet.
I think I can help you a little with that.

The sine wave merely means the the black side varies between pushing really hard, pulling really hard, and everything in between.

>the sine wave is just a representation of the presence of current or voltage?
Voltage. But if flowing, current flows in proportion to voltage, so for a simple resistive load like a lamp, the current also has the same wave.

>if the top is hot and the bottom is neutral compared to the hot where the hot side is being pushed and the neutral side is being pulled then it doesnt seem like it would ever change whether there was a fan load or not in the middle. maybe i have this pictured wrong.
I think so. Perhaps if you just forget about the pulling half for a while it will help.

>it just seems like what goes out and back on these wires would balance out
And indeed it does. Completely.

>and look the same with the equal amounts on top and below, going and coming.
Yes.

>so this means like i said, i hope, that the black wire current still travels on the white wire because it wants to go back to the transformer that way, but its not like its really going that one direction from the black to the white, because you said that it alternates, as in a.c. alternating current.

This is tough for me. The black is the source of the push and the pull. Both do useful work.

>how come there could be more current on the black wire when it is alternating back and forth from the source through the black wire and load and white wire
There can't be.


>and to the transformer which is where it came from to begin with i assume.
Correct.

>some how it seems that it should be equal on both the white and black since it alternates,
Good. Because you got that much right.

> there was more current on the black wire because after going through the fan there wasnt as much current remaining to come out on the white wire.
You just need some different words.
There is less power. And since the current on the white wire already has a good girlfriend (the white wire), it barely looks at you.

The potential current on the black wire is available and looking and desperate (sorry!).

>There's less "push" or voltage on the neutral side of the load because the load has used that energy to do whatever it does.
Not exactly.

>The current IS the same on the hot and neutral for the fan.
Yes.

>The voltage pressure is less on the neutral side of the fan.
Mainly because the white wire provides a free path back to the transformer and secondly because the load impedes the flow of additional current.

However, if you snipped the white wire, the voltage available from it would rise to the level of the black wire. In other words, it would be looking for any way at all to get back home.

Stick with the water analogies-they are the easiest to visualize and compare to electricity at a basic level.

Current = Gallons
Voltage/Potential = Pressure
Ohms/resistance = Water pipe size

When there is a gallon of water coming out of a hose and spraying you, this can be dangerous. (Imagine if you will those giant hoses used to tame riots)

But if the water is just sitting in a bucket(no pressure) it is not dangerous to you. (Disregard the temperature of the water)

So the hot/black wire is the hose and the white wire is the bucket.

To understand electricity(at least AC) any further, I think it is important to understand magnetism and how it causes electrons to flow.

Get a book on electronics basics. That is the best place to start. Trying to pick up bits and pieces from a bulletin board may have you believing something that is incorrect. The locations within the circuit are vital in understanding voltage and current.

The white wire may be at the end of circuit or it may be in the middle. This will make a difference in the dangers associated with touching the wire.

This is not a simple subject and somethings involved with electricity even good electricians and engineers don't understand.

Just want to urge caution in doing any type of electrical work if you're not 100% sure you know what you are doing. Your life is worth more than the couple hundred bucks it will cost hire a qualified electrician. P.S. Make sure your electrician gets a permit and calls for an inspection and shows you the report from the municipality saying the work is approved, if you ever need to get work done.

coulombs = gallons
current (coulombs per second) = flow

Cindy go outsdide, turn on the water faucet/volts, see the water flowing out/current. Now grab the hose in the center and crimp it/resistance, notice the flow/current reduce.

But there is much more than that to electricity, if you have 0 resistance in electricity the current would go to infinity without CB's. That's how you get electrical fires.

I got a good friend that knows everything (well within reason) electrical, even better than my father did, and that's saying plenty. But my Greek friend could not explain a thing understandable to me.

I also had an instructor that taught electricity well, but in the real world he would get you killed.

So take this info as good conversation and not as a tool for exploration.