THE FUNCTION OF BATTERIES

Radio Record, Volume I, Issue 30, 10 February 1928, Page 2

THE FUNCTION OF BATTERIES

1 To explain why we have ‘A’? and "B" batteries in a receiving set, the functions of each, and why one highvoltage and one low-voltage battery is used, it is neeessary to go into an explanation of the principle of the vacuunt tube (or valve) as used for radio purposes. We will attempt to make this explanation as clear and nontechnical as possible. Through the researches of scientists, such as ‘Fhomson, Richardson and Millikan, we know now that when certain metals are heated to incandescence, particles of matter are thrown off. These particles are called electrons and the theory explaining this phenomenon is called the ‘Electron Theory." Incidentally, these electrons are negative particles, and at present the smallest particles of matter known. In 1004 [leming (another scientist) was granted a patent on the device called a ‘‘ieming yalve,’’ which consists of a filament-and-plate clement enclosed in am evacuated glass vessel. In school, in the physics or science class, we learned that positive attracts negative, or vice versa, depending upon which has greater strength. Fleming inserted in his device a battery of high potential. The positive side of this battery was connected to the plate within the vessel, thus making the plate highly positive, thereby enabling it to attract the electrons which were thrown off by the heated filament. This device was of little practical use as far as radio (in those days called ‘‘wireess’) was concerned, until 1906 when DeForest inserted the third element called the "grid," thereby making the most sensitive detector known Now to show how "A" and ‘'B" batteries are concerned. The battery reGuired to heat the filament to imeandescence is called the ‘‘A" battery (probably because it is the first battery to be taken into consideration, of primary battery}. The battery . required to give the plate its positive potential is called the "B" hattery. However, since the filament consumes an enormous amount of current compared to that used by the plate element of the tube, the battery necessary to heat the filament must have a high amperage cepaciy, ranging from 28 to 120 ampetes, depending upon the number of valves used in the receiving set, and the type of valves. In the early davs valves were manufacturcd with _ filaments which required 3ix volts and cot‘sumed about ait ampere At present, due to research and developments made by electrical engineers, we have radio valves which operate from a dry cell or two, and consume only front .u6 to 25 »f an ampere. The "plate" of the yalves consumes very little current, as aforementioned, Int requires an extremely high potential, varying from 225 volts for a ‘soft’ or detector valye, to 90 volts for the erdinary amplifier valve, and about 180 volts for a power-amplifier valve. Ordinary "B" hatteries are constructed (consisting of a number of very small cells) so that, although their amperage capacity is very low, ranging from two to seven amperes (of total ontput) the voltage delivered is high because of the small cells, each delivering 1} volts, being connected in series, it