Glow discharge - good shine

Electric current flows not only in metals, but in liquids and gases. True, the mechanism of electric current flow in these cases is different. In gases everything begins with an electrical discharge. It by its nature can be of several types, one of them - the so-called glow discharge.

To understand what it is, you can get acquainted with the description of the experiment conducted by scientists to demonstrate a similar phenomenon. To conduct it, use a glass tube of a certain length, which has two electrodes at the ends. A DC power supply is connected to them . Two variants of further experiment are possible here, either they begin to gradually increase the voltage to a value of several thousand volts, or they begin to pump air out of the tube to lower the pressure inside to a few mm. Gt; Pillar.

When the pressure is reduced to a certain value, a luminous cord flashes from the electrode to the electrode in the tube. It was a glowing discharge. Its appearance is promoted by a reduced pressure, and it is supported by the secondary emission of electrons from the cathode. The matter is that under normal conditions the gas does not conduct electric current, but under special conditions, for example, such as described, an electric current flows between the electrodes. In this case, positive ions bombard the cathode and knock out electrons from there.

The current flow is due to the formation of such free charge carriers, but the mechanism of their appearance is different. Now the following types of discharges in gases are known: spark, corona, arc and smoldering. The reasons for the current to flow are also different. When we evacuate air from a glass tube, we will eventually get a glow discharge, and when we increase the voltage at the leads of the electrodes - a spark.

In order not to return more to classification, we note that there are independent and non-self-sustaining categories. The types of independent discharges are already listed, and the non-self-sustaining ones arise with any additional external influences.

All kinds of categories are interesting and possess extremely curious properties, but for now let us dwell on one of them. Let's see what the glow discharge is. If you study its external manifestation, you can establish two areas - non-luminous and luminous. Non-luminous is called the dark cathode space, and the luminous one is called the positive column, and it occupies practically the entire volume of the tube.

The color of the glow depends on the gas in which the discharge occurs. Such luminous tubes are used as lamps, so-called fluorescent lamps. Yes, and advertising lights, too, are performed using similar tubes. And the process of decoration and lighting is almost impossible without such products.

However, this is by no means all possible applications of a glow discharge. There are such industries as laser technology and plasma chemistry. In addition, due to the use of a glow discharge, the surface of the tool is hardened to increase its wear resistance, hardness, cavitation resistance.

From other possible applications of the described effect, it can be noted its use in special devices based on the effect of a glow discharge. They can be used to regulate current and voltage, in device protection and amplification devices, oscillators. However, an electric discharge can also be an undesirable phenomenon. Thus, a corona electric discharge with a power line causes power losses, but this does not apply to a glow discharge, which we are now interested in.

Consideration of the electric current in gases made it possible to establish the mechanism of its occurrence, including understanding what the glow discharge is. The variants of its use in industry and engineering are described.