A Qualitative Analysis Of Electrical Discharge In Air

Abstract

The purpose of this paper is to present the fundamental ideas of the gaseous electrical discharge and to experimentally verify those presented ideas. Chapter I deals with the theoretical description of the discharge in a manner that is easy to read accompanied by enough detail to enable various phases of the discharge to be experimentally preformed. Chapter II presents this experimental qualitative analysis. If a potential is applied across two electrodes of an evacuated tube, the phenomenon of electrical discharge through a gas may be observed. There are several general types of discharge that may be witnessed. If a high potential is used and the pressure within the tube is atmospheric, the discharge will take the form of a spark discharge with "explosive like" sounds or a sharp crack. As the pressure is decreased the discharge begins to take on thread like characteristics and then gradually assumes a continuous glow as the pressure is further decreased. This continuous discharge is known as the glow discharge. Another type of discharge which is usually affiliated with high current densities is called the arc discharge. The discharge here appears as a continuous arc from one electrode to the other. Under still other situations the discharge takes the form of streamers which appear on either electrode and extend out some distance and disappear, as shown in Figure 1. There is also one other type of discharge which occurs before any visible radiation and is known as the dark discharge. This phenomenon is termed a discharge since current is passing through the tube at this stage. This paper will deal primarily with the glow discharge since this was the discharge that was experimentally observed.