The Electric Strength of Air under Continuous Potentials and as Influenced by Temperature

The paper describes a series of experiments on the influence of temperature on corona-forming continuous potentials. The observations have been made on three sizes of wire of diameters 0.0251 cm., 0.0803 cm., and 0.0933 cm., and in each case at several values of temperature within the range 5 deg. cent and 70 deg. cent. At each temperature the pressure has been varied from a value in the neighborhood of that of the atmosphere downwards, reaching in the extreme cases the value 6.03 cm. of mercury. Within the range of values reached, as indicated above, the general form of the law of corona, as developed experimentally by a number of other observers, is found to be fulfilled. There are separate families of curves for positive and negative potentials as obtained by varying the pressure for each constant value of temperature. The observations show that under constant conditions as to pressure and temperature a higher value of negative potential than positive potential is required to form corona. As plotted graphically, the results seem to indicate that when larger wires are used corona appears at the same values of both positive and negative potential. The observations, however, have not been extended sufficiently to show this identity of value. This conclusion is at variance with the observations, of a number of other experimenters, in particular those of W. S. Brown, who concludes that with larger values of diameter of wire negative corona may appear at lower values than positive corona.