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Old 02-12-2010, 06:40 PM   #1
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Hypothetically speaking, because you never work with wires hot,,,,,,,,,, when connecting say a ceiling light fixture, power is on, light switch is on, hot wires are nutted,, can you get a shock from the white/neutral wire? I have it in my mind that if the white completes the loop, once the black is connected, you have juice returning in the white.

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Old 02-12-2010, 06:42 PM   #2
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Try it & let us know

Yes the neutral completes the circuit

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Old 02-12-2010, 07:00 PM   #3
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No need to try it. You will get a shock, same as from the hot.
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Old 02-12-2010, 09:47 PM   #4
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Originally Posted by Jim Port View Post
No need to try it. You will get a shock, same as from the hot.
Same as from the hot? Voltage, yes...current, no. Correct?
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Old 02-12-2010, 09:52 PM   #5
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Yes the neutral carries a current and is possible to get a shock on the neutral but most likely you won't feel it.
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Old 02-12-2010, 09:54 PM   #6
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Yes the neutral carries a current and is possible to get a shock on the neutral but most likely you won't feel it.
Really ?

With power on to the light, hot wires connected & your body completing the circuit ???
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Old 02-12-2010, 10:00 PM   #7
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Under various different situations, you can be shocked by the black wire, the white wire, and even the bare ground wire!

Isn't that shocking?

That is why it is best to turn off *all* the power in the house before working on electrical wiring (including ground wires!).
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Old 02-12-2010, 10:16 PM   #8
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I was not stating that the grounded conductor (neutral) would not shock you, I was simply stating that a shock from the neutral would not theoretically be the "same" as a shock from the 'hot'. This is because the current passing through the neutral would be less than that from the hot, because the resistance of the device would reduce the current flow at the point of contact with the neutral. Isn't this true?

Again...I was only questioning the nature of the current at a point of contact of a hot conductor versus an energized neutral conductor.
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Old 02-12-2010, 10:32 PM   #9
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I guess another way to note the difference is to ask, Would an amp clamp give the same values if one measured the hot conductor and neutral conductor of any given device or circuit?
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Old 02-12-2010, 11:40 PM   #10
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Let's use ground as the reference point and we assign it a value of zero (volts). Relative to ground the hot wire is 120 volts. Some voltage drop occurs in the wire out to a light fixture, say one volt, so at the light hot terminal the voltage relative to ground is 119 volts. So the light itself gets 119 volts to work with. Wait a minute. The current going back on the neutral (the same number of amperes as came out on the hot wire) loses a volt there too so the light itself really gets 118 volts. At the panel the neutral is connected to ground so there is a zero volt difference there.

Out at the light, the terminal connected to the neutral (and which should be connected to the socket shell if it is incandescent or screw in compact fluorescent) is at one volt relative to ground. It is very unlikely to get electrocuted by touching that terminal with the light turned on using one hand and touching ground (for example a heating radiator) with your other hand but if you had two extra lengths of wire, one running to each of those places, and touched the loose ends of those two wires to your tongue you probably would feel a shock.

One characteristic of electricity is that a smaller current going through a wire or through a light bulb suffers a smaller voltage drop. Specifically the voltage dropped equals the current flowing times the resistance in that portion of the circuit such as a light bulb filament.

Suppose a loose connection develops in the neutral as it daisy chains back to the panel through a few receptacles. The current stops, the light goes out. We now have zero amperes flowing. Zero volts are dropped in the hot wire coming out from the panel. Zero volts are dropped in the light bulb where 118 volts were dropped a while ago. At the break in the neutral, the end coming back from the light is now at the full 120 volts and the other broken end going back to the panel is zero. It takes perhaps a hundredth of an ampere to kill a person depending on what parts of his body are touching two wires at different voltages and chances are the voltage drop in the rest of the circuit including the light bulb won't be that much leaving perhaps 90 to 100 volts across where the loose connection in the neutral (and a careless person working on it) are.

About the amp clamp. In a simple circuit, for example hot coming out to one light or appliance and neutral going back to the panel, measuring the hot and measuring the neutral will show the same current. Same idea with water in a recirculating fountain or forced hot water heating system, the volume of water returning equals the volume of water going out. The math gets a little complicated when we discuss branches in the circuit with differnet lights or appliances on the various branches.
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Last edited by AllanJ; 02-13-2010 at 12:05 AM.
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Old 02-12-2010, 11:56 PM   #11
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For the purposes of a DIY internet forum, I think it is a good policy to advise people that they could be shocked by any wire and to turn all the power off...

Of course the more knowledgable people here will know about different situations and how to test for this. (You guys know what is what.)

What I am worried about is MultiWire Branch Circuits (MWBC) and people who don't know the difference with what they are working on.

Or the case of a loose/disconnected main conductor.

Or situations where the ground wires were not connected to the main panel (like new additions to a house) and there is an appliance hot to ground malfunction. Etc.

MWBC Dangers...
http://www.google.com/#hl=en&source=...a94940edcea411
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Old 02-13-2010, 07:12 AM   #12
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I thank you for the replies, its not so much that I was trying to "win" the arguement about the white wire, I'm trying to understand electricity. I don't take it lightly.
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Old 02-13-2010, 04:29 PM   #13
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NEVER TRUST NEUTRALS! they could be shared with other circuits and unless all of the circuits that it is shared with are off, you have the potential to get shocked, or worse yet become the path that bonds the neutral to ground which can kill you if it travels through your body to ground, check double check, neutrals are actually more dangerous than hots because a 120 hot might hurt a little, but your probably on the line side and therefore not experiencing any portion of the load, but a neutral may have a load at one end and you could complete that circuit to ground and all the amperage goes through you.
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Old 02-13-2010, 06:49 PM   #14
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AllanJ got this right. If the neutral is PROPERLY connected, the maximum voltage on the neutral can only be created by the voltage drop from the device to the neutral grounding connection at the panel. As noted by AllanJ, V = IR, where V is the voltage drop, I is the current and R is the resistance. Since the resistance of a neutral wire is very low, the voltage drop is quite low. You receive a shock due to voltage potential difference between the wire you touch and ground, therefore touching a PROPERLY CONNECTED neutral will result in at most a shock from less than 1 volt. The current flowing in the neutral is totally irrelevant to the shock potential. Since the hot wire is at 120 volts (or 240 if it is 240 service), it is easy to receive a fatal shock by touching a hot wire and ground simultaneously.

As noted by several of the posters, unusual neutral connections or neutral faults can result in a wide variety of problems that can certainly lead to shocks by touching the neutral. However, that was not the question posted.
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Old 02-13-2010, 10:51 PM   #15
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While it was a mouthful, everything AllenJ is saying is right.

Technically, Danial made one mistake:
"The current flowing in the neutral is totally irrelevant to the shock potential."

Actually, the current flowing in the neutral sets the shock potential. Because of that equation V=IR, if you double the current in a circuit, you double the voltage drop. So in AllenJ's example of a 1v drop in the hot wire, 118v drop across the light, and a 1v drop in the neutral, if you add more lights such that the current doubles, you would then have a 2v drop in the hot, 116v drop across the lights, and a 2v drop in the neutral.

Now from a practical stand point, there isn't any difference in "shock potential" in 1v vs. 2v. But I hope it helps explain the THEORETICAL aspect.

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