Energy conversion in electronic devices

摘要

An electronic oscillator is a ????????machine???????? for the conversion of d.c. power into a.c. power, with electrons as moving parts. By means of the Maxwell-Poynting theory the conversion process can be localized, and analysed into the elementary contributions of volume elements. Integral relations for the whole valve can be expressed in various forms of which the following lends itself best to physical interpretation: The power consists of three parts. The first is ????????collector power,???????? determined entirely by the potentials and currents of the electron collectors. The second is ????????transit power,???????? produced by changes of space potential during the flight of the electrons. The third power component is due to electric fields induced by alternating currents. This is negligible under quasi-static conditions, but becomes of the same order as the transit power when the valve itself begins to emit radiation. All methods of producing alternating electron currents can be reduced to emission, deflection or transit time modulation. A threefold division is adopted also for the sources of the electromagnetic field. Space charges and their complementary surface charges play no direct part in power conversion. An exhaustive classification of all power-producing processes under nine headings is obtained, and is applied to a few special examples.