While replacing the plug on an extension cord I noticed that one of the main wires had a couple of silver strands in it. The other main wire was all copper strands. Corrospondingly the plug had one silver screw, one copper screw, and of course a green one for the ground wire.

Here is the question. Why does it make any difference which side of the plug the main wires are attached to? With alternating current would it not operate the same no matter which wire was used for each side of the plug as long as the green wire was attached to the ground screw?

I'll stab at this one.  The reason there is dedicated hot and grounded conductor(neutral) is to protect idiots from getting lit.

 The Neutral is ALWAYS connected to the screw shell on a light bulb, NOT the live "HOT," wire.  The Hot wire is on the bottom of the screw shell way down in there.

Dedicating conductors is safer.

It won't make a difference in operation, BUT you
're looking at a safety issue.  The copper screw on the plug should connect to the all-copper strand on the cord.  That's the hot lead; on some cords the lead will also have small ribs on the insulation.  If your plug is polarized, the copper screw will connect to the narrow prong.

Silver screw on the plug goes to the conductor with the silver strands...that's the neutral lead.  It's grounded at the electrical box, but NOT at the plug.  With a polarized plug, you'll be connecting to the wide prong.

Green goes to ground.

Important thing is that the off-on switch on the appliance needs to break the HOT wire.  If it breaks the neutral, the appliance will work fine, BUT hot current is applied to it at all times.

For an explanation of why this is important, see...[url]http://www.handymanjim.com/d.htm[/url]  page down to "The Way It All Works".



-hanko

Neutral switch legs =[shock]

The silver strands are Zinc coated.

In a single phase AC box you have hot and neutral. For now, we will ignore the 3 conductor, earth ground.
On a outlet receptacle: The left slot is usually neutral (larger blade) and the other is "hot" (smaller blade).
The earth ground and neutral can be considered the same however, when the ground is absent, polarity can matter because......
Most two-prong electrical equipment will not ground parts of the chassis. If it were to ground the chassis to the neutral, you can see the problem if you were to reverse the plug.

All 3 prong equipment will ground the chassis to the earth ground (the round conductor prong). Especially important if this equipment is mostly a metal chassis or body.

If you peer into a breaker box, the inside railes are the "unfused" and the outside are "fused" (because of safety breaker), the breakers connect across the two. The bare copper dedicated ground will connect to a rail that also shares the neutral connection. The rail will follow a braided conductor to the box. There is always also a dedicated real earth ground per most electrical codes.

In theory if all of the sockets are wired the same and two near by devices have a short, then both devices would be at the same potential.  You could then touch both of them and not get shocked.  In theory.

Do not refer to right or left on a 110 volt nominal recept.  If it is up side down it will be wrong.  It is legal to install (green lug) equipment ground up or down.  

It looks like another electrical engineer is trying to kill people. [}:D]

Your right. My bad.
I just was trying to point out that when looking at a outlet receptacle, the left one is always the wider blade. This is the neutral.

Now if your installing wires to a plug it may be helpful to know that the fatty is neutral. As NEKKID80 pointed out; it is not good to wire ANYTHING in reference to a arbitrary reference (up, down, right, left).

Other than the "arbitrary," screw up Boomholzer is CORRECT in his posts.[peep]

If I am installing outlets at waist high or higher.......(like in garage) I like to install the receptacle "upside down" with the ground conductor on top.
At one time, I thought this was better because it combated the weight of the cord pulling on the plug and kept the plug seated in the receptacle. Now I think that I am just NUTZ.

BTW; My EE knowledge taught me nuttin about this stuff. I know about chips, electronics, and other garbage.
I learned what little knowledge I have from hands on work and by working with residental contractors. Plus, my pop can doing and everything when it comes to houses. He is the true jack-of-all-trades and master of all.

If it was really important the NEC would require one way.

IMO face up (ground on bottom) is correct due to the fact that the ground prong being longer then the conductors, will be last to fall out if the cord is pulled.  

There are arguements for and against both ways and after analyzing it all I determined face up is best.  

I probably just flip-em upside down to make me feel cool, like I know what I'm doing [:D]. Plug

IIRC the standard electrical outlet (20Amp) was designed to have the ground lug in the up position (an upside down face if you look at it) of course this was way back when it was designed ...
The problems that can occur (and it happens with electricians.. ask the one that bought me a new laptop 3 years ago) is that when two devices are plugged in to different receptacles and polarity is not observed and one has the hot on left and the other has hot on right (both with the ground lug down)and a GROUND is connected between the 2 devices (IE: an RS232 connected cable for data transfer or programming) there is a complete circuit that ends up with AC on the ground and that can be disastrous to the equipment on both ends of the connecting cable as well as usually causing the connecting cable to flare and become a fuse link and open...
That electrician ended up buying (thru his insurance I am sure) a new telephone PBX system for the tune of $250,000.00 and replacing my measly old laptop for $2,100.00...
I never plug in again without first checking with one of those cheap 3 prong circuit testers...
Ted...

you'll also note, that when putting a connector on your extention cord (3 cond) that you have the right one if the wires as they twist will line up with the corosponding lug on the connector. in otherwords, the wires should not cross to make proper connection with the lugs.

Always a good idea.

When I bought my 70 year old house I replaced everything but the entrance panel, which had been replaced around 1970. Unfortunately, they just spliced in all the old stuff to the new panel. The original wiring was first rate knob and tube, but was trashed in various renovations throughout the years. I found all kinds of wonderful things like splices inside walls with no wire nuts or even electrical tape and bare #14 wire fused at 30 amps, buried under blown in fiberglass insulation. I'm amazed the place didn't burn down.

I know what you mean MadMatt. We bought a house in CA that had been worked on by the owner, who was supposedly a licensed contractor. I saw stuff that kept me up nights even after I had it fixed. Like you said, I don't know what kept it from burning.

coyote3