An oscillograph study of corona

A method of obtaining oscillograms of the charging current of a ten-foot (3 m.) length of wire is described. The method is to multiply this charging current — which is of the order of 0.005 amperes — by 100, by passing the current through the primary of a 1 to 100 milliampere current transformer, the secondary of which is closed through an oscillograph vibrator. The paper contains a series of oscillograms obtained by this method, showing the wave form of the charging current of wire surrounded by corona. These oscillograms were taken at air pressures from atmospheric to 0.13 cm. of mercury. They show the marked asymmetry in the current after corona forms, the relation between power loss and impressed voltage, the start of corona after switching, the marked difference in the results at high and low air pressures, etc.