Recently I wrote about wiring wall outlets. This time I want to talk about wiring wall switches and light fixtures, If you're ever looked at an installed wall switch, you might see that there are two black wires attached to it, and no white. Or you might see a black and a white. Or there might be a black and a white with a black mark on it. Does it make a difference? And if so, what is the difference? Let's find out. Again, whenever you look at wires in walls or drawings of them, what you're seeing is the cables that contain the wires. It appears that there are a few big fat wires. Actually what counts are the smaller wires inside the cables. When you're looking at cables, it appears that there's one wire coming from the service panel, and none going back. The fact is that inside the cable are at least two wires. For simplicity's sake, I'll write here about two wires, even though in construction done in the last 40 years, there are three - one for grounding.
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