Before the advent of solid-state electronics, vacuum tubeswere widely used in ra

Question

Before the advent of solid-state electronics, vacuum tubeswere widely used in radios and other devices. A simple type ofvacuum tube known as a diode consists essentially of twoelectrodes within a highly evacuated enclosure. One electrode, thecathode, is maintained at a high temperature and emitselectrons from its surface. A potential difference of a few hundredvolts is maintained between the cathode and the other electrode,known as the anode, with the anode at the higherpotential. Express your answer numerically in meters per second.

Explanation / Answer

   Distance between cathode andanode   =   radiusof anode   -   radiusof cathode   =   0.5580   -   0.06200          d   =   0.4960   cm   =   4.960* 10-3   m    Strength of electric field between anode andcathode   E   =   V /d   =   230 / 4.960 *10-3    E   =   4.637* 104   V/m    Force onelectron   F   =   E *e   =   4.637 * 104 * 1.6* 10-19   =   7.42 *10-15   N    Acceleration   a   =   F/ m   =   7.42 * 10-15 /9.1 * 10-31   =   8.15 *1015   m/s2    Third equationis      vfinal2   =   vinitial2   +   2* a * d    =>   vfinal2   =   02   +   2* 8.15 * 1015 * 4.96 * 10-3          vfinal   =   (8.085* 1013)   =   8.99 *106   m/s          vfinal   =   (8.085* 1013)   =   8.99 *106   m/s

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