The Effect of Initial Velocity of Electrons Upon the Anode Current of a Vacuum Tube

Abstract

Effective initial velocity of electrons emitted from a tungsten filament at different temperatures.—The initial velocity of electrons causes deviation of anode-current, anode-voltage relation of vacuum tubes as derived from the space charge equation. By eliminating the other causes of deviation, the author measured the degree of deviation of the current-voltage curve from the three-halves power law at various filament temperatures, and found that the effective initial velocity of electrons varies from about 0.5 volt at 2250°K to 4 volts at 3000°K. The effective initial velocity seems to be independent of the dimensions of the electrodes.