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|electron tube |
A sealed glass tube containing either a vacuum or a small amount of gas, in which electrons move from a negatively charged electrode, the cathode, to a positively charged one, the anode. The cathode is usually heated by an electric current to free the electrons. Other electrodes in the tube can vary the electric or magnetic fields in the tube to control the strength and direction of the moving electrons. Electron tubes are used to amplify signals, rectify AC currents, and produce x-rays, among other uses. They have been mostly replaced by transistors but are still used in television screens, computer monitors, and microwave technology. Also called valve. See also vacuum tube.
device usually consisting of a sealed glass or metal-ceramic enclosure that is used in electronic circuitry to control a flow of electrons. Among the common applications of vacuum tubes are amplification of a weak current, rectification of an alternating current (AC) to direct current (DC), generation of oscillating radio-frequency (RF) power for radio and radar, and creation of images on a television screen or computer monitor. Common types of electron tubes include magnetrons, klystrons, gyrotrons, cathode-ray tubes (such as the thyratron), photoelectric cells (also known as phototubes), and neon and fluorescent lamps.