An Attempt to Verify the Theory of the Long Spark of Loeb and Meek

Abstract

In an attempt to verify the theory of the long spark of Loeb and Meek, d.c. sparking potentials in a plane parallel gap in air have been measured as a function of plate separation and pressure at and below atmospheric pressure. Below atmospheric pressure, the sparking-potential curve as a function of gap length at constant pressure, displays a peculiar levelling-off at large gap lengths. This has been shown to be due to field distortion of a pressure-dependent type. This field distortion is, in large measure, caused by the walls of the large chamber used in this study. This field distortion prevented the verification of the Loeb-Meek theory. However, there is considerable evidence for believing the results at atmospheric pressure to be valid. Meek's equation represents the data accurately at atmospheric pressure. Water vapor causes a small but definite scattering in sparking potentials.