Plug Explanation

Thanks for the Ebay tip, to all who suggested it. I just ordered 3 wall sockets, 1 extension cord socket, and 5 plugs for 71 bucks. That is a much better price than I expected to pay.

Thanks,
Chris
 
This thread has been very helpful to me. I too vote for it to become a sticky.

Our house, shop included, is a mixture of old (circa 1947) and newer wiring. All typical single phase 120/240 residential service.
I have done most of my own electrical work with the guidance of an electrician when necessary. I follow instructions carefully but I don't always understand why things have to be done a certain way.

For example our power comes in on two insulated wires carried by a bare cable that is structural. Does this bare cable become the white wire or the ground?

Also, why are 120v receptacles and plugs polarized? With alternating current does the polarization not change at the rate of 60 cycles per second?

Sorry for the silly questions but I am very challenged when it comes to understanding electricity.
 
Tozguy said:
This thread has been very helpful to me. I too vote for it to become a sticky.

Our house, shop included, is a mixture of old (circa 1947) and newer wiring. All typical single phase 120/240 residential service.
I have done most of my own electrical work with the guidance of an electrician when necessary. I follow instructions carefully but I don't always understand why things have to be done a certain way.

For example our power comes in on two insulated wires carried by a bare cable that is structural. Does this bare cable become the white wire or the ground?

Also, why are 120v receptacles and plugs polarized? With alternating current does the polarization not change at the rate of 60 cycles per second?

Sorry for the silly questions but I am very challenged when it comes to understanding electricity.
Click to expand...

The bare cable in your overheat power company service drop is the neutral. It is connected to ground at your main breaker panel. Ground for your house is provided by either a ground rod or by buried metal water piping.

The distinction between neutral and ground is tricky. They are both connected to ground, but they serve different purposes. The National Electric Code (NEC) refers to neutral as the "grounded" conductor, and safety ground as the "grounding" conductor. Not a good choice of words for the casual reader! The way I think of it is that the white neutral aka "grounded" conductor is a load carrying wire that just happens to be grounded. The green "grounding" conductor does NOT carry load, its only purpose is to provide safety grounding for the exposed metal parts of equipment.

So going back to your service drop - the load current returns to the utility pole thorough that bare neutral wire. But load current does NOT flow in the wire going to the ground rod or water pipe.

The reason for polarized plugs is not about the polarity of the voltage - as you say, AC switches back and forth all the time. It is a safety thing. The hot side is swinging positive and negative, but except for the brief instants when it crosses zero, it is always at a dangerous voltage. The neutral side of the circuit is grounded at the main panel and usually within a volt or so of ground everywhere else, so it is much safer. Now think about a lamp with a switch. If the switch is in the hot side, when you turn the lamp off, both sides of the socket are safe to touch (for example when changing the bulb). But if you plug it in backwards, the switch is in the neutral and turning it off doesn't actually remove power from the socket. If you touch the inside of the socket and ground at the same time you get zapped. Polarized plugs are an attempt to keep the switch on the hot side of the circuit.
 
I thought I was pretty well versed on plug types. Learned some new things, thanks very much for sharing this thread.
 
JMK, a big thank-you!
Now I get it and it feels GOOD to finally see the light, no pun intended.
This place is GREAT!
 
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