I was talking with a friend after a LASFS meeting yesterday, and the conversation turned to Thomas Edison and his famous quote, "I haven't had a thousand failures, I've discovered a thousand ways not to make a light bulb." (Or whatever the number is.)
I mentioned the other accidental discovery Edison made, when he ran a cold wire next to a hot filament. He discovered electricity would flow from the hot filament to the cold wire.
This "Edison Effect" turned out to be useful in circuits. If you wanted current to flow in only one direction, you cold put one of these bulbs in the circuit, and current would flow from the hot wire to the cold one, but not the other way. This gadget would be named, variously, a "valve", and eventually, a "diode".
If you put a grid between the two wires, you could change how much electricity got from the hot wire to the cold one at any given voltage. One of the applications was that, if you got the voltages right, you could impose a weak signal on the current going into the grid, and you would get a strong signal imposed on the current coming through the diode. (Well, now a "triode", because it has three elements.)
My friend realized, with some astonishment, that Edison had accidentally invented at least two major industries, radio and computers.
I took electronics in college in the early 80s, at which time vacuum tubes were relegated to an appendix in the textbook. Does anyone still study the things nowadays?
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