Читать книгу Roentgen Rays and Phenomena of the Anode and Cathode онлайн

16 страница из 42

8. Wheatstone’s Experiment. Duration of Spark. Phil. Tran. 1834.—The short duration of an electric spark produced by a single disruptive discharge is easily made apparent by a rapidly rotating disc, having radial sectional areas of different colors. With reflected sunlight, the colors seem to blend into one tint upon the principle of the persistence of vision; (See Swain’s experiment. Trans. R. So. Edin. ’49 and ’61.); but when viewed by the flash of a spark, the colors are seen as distinctly separated as if the disc were at rest. By calculation, based directly upon a series of experiments, he found the duration of the spark to be about .000042 sec. It was discovered also, by the rotating mirror, that the apparently single spark was composed of several following each other in quick succession, and he concluded that the current during the discharge was intermittent. He considered each of the divisions of the spark as an electric discharge. Prof. Nichols, of Cornell University, and McKittrick obtained curves indicating the variation of E. M. F. during the existence of a spark. Trans. Amer. Inst. Elect. Eng. May 20, ’96.