The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Cocking, W.T. Television Receiving Equipment. New York: Iliffe, 1940.||"A supply of some 3,000-6,000 volts is needed for the final anode lower voltages for the other anodes."||3–6 kV|
|Middleton, H.A. Master Receiving-Picture Tube Substitution Guide Book. New York: Rider, 1959.||"Therefore, a design Center Maximum Rating of 16,000 volts is equivalent to and absolute maximum rating of 17,600 volts."||16–17 kV|
|Cutnell, John D. & Kenneth W. Johnson. Physics. 4th ed. New York: Wiley, 1998.||"In a television picture tube, electrons strike the screen after being accelerated from rest through a potential difference of 25,000 V."||25 kV|
|Goldwasser, Samuel M. Repair: Safety! sci.electronics FAQ. 30 July 1996.||"TVs and monitors may have up to 35 KV on the CRT but the current is low -- a couple of milliamps."||35 kV|
|Sprott, J.C. Magnetism. Physics Demonstrations University of Wisconsin, Madison. 30 May 1997.||"One should stress the fact that the electron beam consists of a large number of negatively charged electrons moving at a good fraction of the speed of light (about 0.25 c for a typical acceleration voltage of 17 kV)."||17 kV|
The experimentation of creating a television system began in the late Nineteenth Century. In 1884, a German scientist, Paul Nipkow proposed the first workable television system. In 1900-1920 early versions of the picture tube started appearing. Methods of amplifying electronic signals and the formulation of the electronic scanning principle became the basis of modern television. A television is an electronic system that produces images on a screen. This is currently done with a cathode-ray tube, which contains an electron gun that must be operated at a high voltage. The electron gun shoots a high-energy beam of electrons toward a phosphorescent screen, creating a bright spot that appears where the beam hits the screen.
A full screen image is formed when the electron beam is deflected in the vertical and horizontal directions either by magnetic fields or the electrostatic effect of electrodes within the tube. The magnetic fields and the electrostatic effect of electrodes within the tube are produced by coils found in the neck of the tube.
Some cathode-ray tubes use multiple beams of electrons, displaying more than one color. These are made for television, oscilloscopes, computer terminals, automated teller machines and radar displays.
The voltage of a television picture tube has increased gradually. In the 1940s only 3000-6000 volts were needed for the final anode. Today, 25,000 volts are typical as television has advanced from small black and white sets to larger color screens.
Michelle Hong -- 2000
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