In normal 110-120 VAC wiring, black is by far the most likely color for
"hot." I teach it this way...
Black is death.
* * * * *
Perhaps the next most likely color to be hot, but usually in 4-wire
220-240 VAC wiring, is red. These 4-wire cables usually contain black,
red, white, green/bare. Here we can remember...
Red is redhot (as well as black is death).
* * * * *
As for green being ground, I tell students to remember...
Green grass grows on the ground.
* * * * *
It is correct, as Bernard pointed out, that the white wire should be
called neutral rather than ground. The reason is that a ground wire
(such as the chassis ground) is not supposed to carry any but negligible
current during normal operation. The neutral is a current carrying
wire, and that is why we should not call it ground even though it is
connected to ground at the circuit-breaker box. Think of it in the
following way...
If you have a device that is turned on and operating normally, and
somewhere between the device and circuit breaker you cut the green wire,
you should be able to touch (simultaneously)both cut ends and not be
shocked. By cutting the ground wire you have not broken a current path
(unless the device is defective).
On the other hand, if you cut the white (neutral wire) and touch both
cut ends simultaneously, you are in big trouble.
This is also similar to why you don't put the on/off switch in the
neutral wire. That turns the white wire from the device to the switch
into a hot wire whenever the switch is turned off. It also means that
when you turn off the switch and think it is safe to work on the device,
you are sadly mistaken, especially if there are any grounds around that
you might also touch while working on the device.
Anyway, even though we are not supposed to call white ground, I often
hear electricians say "snow falls on the ground." I suppose this is
appropriate at the circuit breaker box where you indeed want to connect
the white wire (and green wire) to the ground bus.
Better, from an electrical viewpoint, is to say "white is a neutral
color because it goes with anything." The problem is that colorwise
black probably goes with everything also.
* * * * *
Summary....
Black is death,
Red is redhot
Green grass grows on the ground
White is a neutral color
less good - White snow falls on the ground.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu
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