A.C. or D.C. Resistance?

Radio Record, Volume IV, Issue 41, 24 April 1931, Page 32

A.C. or D.C. Resistance?

‘ TH phenomenon .known as skin -effect, or the peculiar property of alternating current: especially at. high frequencies to travel.only through the outer portion and not through the core of a conductor, is generally ignored in figuring resistance values for radio purposes. Thus the radio worker is frequently puzzled by the fact that a given solid resistor, rated at a given resistance, actually has considerably higher resistance value in actual use. He may hasten to blame the resistance manufacturer, whereas he has only a: wellknown electrical ‘phenomenon: to blame, A solid conductor offers considerably greater resistance to high-frequene’, current than to direct current, ‘due } the skin- effect. . oo A It is for the above-mentioned. reason that the metallised resistance is finding more and more applications in radio work. Such a resistance, having a metallic coating deposited: ona glass filament, presents. a virtually uniform resistance to either a.¢. or d.c.-energy. Since there is no. core to such a resistance unit, the a.c. or .d.c. energy flows through practically the same thin film or skin. Therefore, the resistance value is the same in either case, and there is no chance for error as when using solid resistance units. :