Vacuum Tube
In electronics, a vacuum tube, electron tube (in North America), thermionic valve, tube, or valve is a device controlling electric current through a vacuum in a sealed container. The container is often thin transparent glass in a roughly cylindrical shape. The simplest vacuum tube, the diode, is essentially an incandescent light bulb with an extra electrode inside. When the bulb's filament is heated white-hot, electrons are boiled off its surface and into the vacuum inside the bulb. If the extra electrode (also called a "plate" or "anode") is made more positive than the hot filament, a direct current flows through the vacuum to the anode (a demonstration of the Edison effect). As the current only flows in one direction, it makes it possible to convert from AC current applied to the filament to DC current.
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Famous quotes containing the words vacuum and/or tube:
“Teenagers who are never required to vacuum are living in one.”
—Fred G. Gosman (20th century)
“Even crushed against his brother in the Tube the average Englishman pretends desperately that he is alone.”
—Germaine Greer (b. 1939)