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.