Daily Facts
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The Edison Effect

July 4th Fact-of-the-Day

Thomas Edison created a vacuum-tube diode in 1883, but didn't understand how it worked or appreciate what could be done with it. There was a significant problem at that time with soot collecting inside electric light bulbs as filaments burned (that problem still exists, but soot is less of a problem with modern designs). Edison placed a metal plate inside an evacuated light bulb, brought a wire from it outside the bulb, and applied voltage between the wire and the filament in an attempt to attract soot particles to the plate. He discovered that current would flow between the filament and the plate in one direction, but not in the other. Neither he nor anyone else at that time could explain why that happened. He pursued other interests and didn't investigate the phenomena further, but his discovery became known as the Edison Effect and provided the fundamental basis for development of all vacuum tubes used by the electronics industry since that time. ©2005 Martek International All rights reserved.


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