According to the general conception of the nature of electric current, gas in its normal state is an excellent insulator, since this space is very small positively or negatively charged particles.However, if dramatically increase the total voltage of the space filled with gas, the amount of ions and electrons therein increases considerably, resulting in the formation and appearance of emission current.
The above is the process when a dependent charge, that is, one in which the current arises only under the influence of external forces, is transformed into an independent.
Self-discharge is characterized in that the positively charged ions and negatively charged electrons appear in it as a result of processes that occur in the discharge space, that is, the number of charged particles in it is not reduced even if you remove the external voltage source.
Depending on the mechanism of transition into an independent non-self-discharge, the following types of discharges:
- corona discharge.This is one of the most interesting types of discharges that is formed when the gas pressure is very high, and the field in which it is extremely nonuniform.To this heterogeneity was formed, the surface of the electrode must be very large, and the surface of another - is very small.Corona discharge may occur as the voltage at the positive electrode and a negative test.If you increase the voltage, according to Ohm's law, and to increase the current, which will lead to the fact that it will increase dramatically in size.Corona discharge can be seen in the wild, when the electrical corona formed on the top of masts or trees.
2. glow discharge.To obtain such a discharge, it is necessary to start up current through electrodes of several hundred amperes, and then gradually to pump air from the cylinder.In this case, the air pressure is gradually decreased, and in the rarefied space of the breakdown of gas, which is reflected in the dim glow of a lace.If you continue to pump out the air, it takes all the space illumination of the cylinder.Glow discharge we can see in discharge tubes, as well as energy-saving lamps. - spark discharge.Type of discharge, which is a sudden, abrupt conversion of gas from the dielectric to the conductor.This happens in cases where there is between the electrodes sufficient capacity to gas breakdown occurred.It is accompanied by a bright flash, which can harm human health.
- arc.It was such a discharge is formed between the carbon electrodes used in the welding work.Temperature formed in the so-called "crater arc" reaches 4000 degrees Celsius.For arc must be permanent cathode heating to a certain temperature.When the temperature reaches a critical level, the thermionic emission starts, whereby an electric arc occurs.
and corona discharge and arc and glow are extremely dangerous to humans, so those whose work is related to these processes must comply with all safety regulations.
