Abstract
THE control of energy at distances of thousands of miles without any other medium than the aether has been made possible by the evolution of the thermionic valve. This remarkable invention can be described briefly as a highly exhausted glass bulb, in which is mounted a tungsten or tantalum filament heated by a battery giving about 6 volts. Electrons are emitted by the heated filament. The filament is surrounded by a grid or gauze cylinder, which is insulated and kept at the negative potential of the filament, while a plate of metal mounted inside the bulb is kept at a high potential of from fifty to several hundred volts by means of a battery or some other source of continuous current. The bulb is highly exhausted, and while the grid is kept at a normal negative potential, steady current passes from the filament to the plate or anode, but as soon as the grid is made slightly positive or negative, the current passing between the filament and anode by virtue of the electronic conductivity is increased or decreased. A valve can be used as a rectifier, as it can be made unilateral in conductivity by suitable adjustments of “grid potential.” It can also be regarded as an inertialess relay, it being only necessary for the grid to be affected by the most minute change of potential for the valve to become more or less conductive, when it may be used indirectly to close a circuit and control magnetic or electrical operations.
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JOSEPH, J. Applications of the Thermionic Valve1. Nature 109, 522–523 (1922). https://doi.org/10.1038/109522a0
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DOI: https://doi.org/10.1038/109522a0