According to the general idea of the nature of electric current, gas in its normal state is an excellent insulator, since there are very few positively or negatively charged particles in this space. However, if the total voltage of a given space filled with gas is sharply increased, the number of ions and electrons in it will increase noticeably, which will lead to the formation of a current and the appearance of a glow.
The above is a process when a non-self-sufficient charge, that is, one in which the current arises only under the influence of external forces, turns into an independent one.
Self-discharge is characterized by the fact that positively charged ions or negatively charged electrons arise in it as a result of processes that occur in the discharge space itself, that is, the number of charged particles in it does not decrease, even if the external voltage source is removed.
Depending on the mechanism of transition of a non-self-sustained discharge to an independent one, the following types of discharges are distinguished:
- Corona discharge. This is one of the most interesting types of discharges, which is formed when the gas pressure is very high, and the field in which itis found to be extremely heterogeneous. For such an inhomogeneity to form, the surface of one electrode must be very large, and the surface of the other must be extremely small. Corona discharge can occur both with a positive voltage on the electrode, and with a negative one.
- Spark discharge. A type of discharge that is a sudden, spasmodic transformation of a gas from a dielectric to a conductor. This happens when there is sufficient potential between the electrodes to cause gas breakdown. It is accompanied by a bright flash that can harm human he alth.
- Arc discharge. It is this discharge that is formed between the carbon electrodes used in weldingworks. The temperature formed in the so-called "arc crater" reaches 4000 degrees Celsius. To obtain an arc discharge, it is necessary to constantly heat the cathode to a certain temperature. When this temperature reaches a critical level, thermionic emission will begin, resulting in an electric arc.
If you increase the voltage, then, according to Ohm's law, the current strength will also increase, which will lead to the fact that it will sharply increase in size. Corona discharge can also be seen in natural conditions, when an electric corona is formed on the tops of masts or trees.2. Smoldering discharge. To obtain such a discharge, it is necessary to run a current of several hundred amperes through the electrodes, and then gradually pump air out of the cylinder. In this case, the air pressure gradually decreases, and a gas breakdown occurs in the rarefied space, which is expressed in a dim glow in the form of a lace. If you continue to pump out air, then this glow will occupy the entire space of the cylinder. We can see a glow discharge in gas discharge tubes, as well as in energy-saving lamps.
Both corona, arc, and smoldering are extremely dangerous for humans, so those whose work is related to these processes must comply with all safety regulations.
