Measurements of natural and artificial point discharge

Abstract

Assuming spherical symmetry, an approximate form of the current-voltage relationship has been derived for a single point and the constants involved verified experimentally in the laboratory, under controlled conditions. When a single point was replaced by a multiple-point system the total point-discharge current through the latter was found to be a function of the point separation and the clearance of the points from the H.T. plate. The current through a system of multiple-points of different starting voltages obeyed an approximate cube law, later derived theoretically, similar to the case of trees and small plants. The fraction of the point - discharge current in a living tree bypassed through a low resistance galvanometer has been found to increase with total point-discharge current, because the impedance of the tree in between the two electrodes increases and the reactance of the bypassing circuit decreases. The resistance of the tree was found to increase with time after application of the voltage and also to increase with decreasing voltage when measurements were made of steady currents; no such effect was observed with instantaneous currents. The effect of the wind on the point-discharge current through a single as well as multiple-point system has been studied. The relation between the point-discharge current, point voltage and wind speed has been derived empirically, using a method of multiple regression analysis. The quantity of charge per pulse, as calculated from the ratio of the average current and frequency of the pulses, was always found to be greater than that calculated by integrating the pulse over the time of decay. When a wind was applied parallel to the electron current, the quantity of charge per pulse increased linearly at first and then reached a saturation stage; a very high wind was however needed to get any noticeable effect.