Dielectric is a material or substance that practically does not transmit electric current. This conductivity is due to the small number of electrons and ions. These particles are formed in a non-conductive material only when high temperature properties are achieved. About what a dielectric is and will be discussed in this article.
Description
Each electronic or radio conductor, semiconductor or charged dielectric passes an electric current through itself, but the peculiarity of a dielectric is that even at a high voltage over 550 V, a small current will flow in it. An electric current in a dielectric is the movement of charged particles in a certain direction (it can be positive or negative).
Types of currents
The electrical conductivity of dielectrics is based on:
- Absorption currents - a current that flows in a dielectric at a constant current until it reaches an equilibrium state, changing direction when it is turned on and when voltage is applied to it and when it is turned off. With alternating current, the tension in the dielectric will be present in it all the time while it is in the action of an electric field.
- Electronic conductivity - the movement of electrons under the influence of a field.
- Ionic electrical conductivity - is the movement of ions. It is found in electrolyte solutions - s alts, acids, alkali, as well as in many dielectrics.
- Molion electrical conductivity is the movement of charged particles called molions. It is found in colloidal systems, emulsions and suspensions. The phenomenon of molion movement in an electric field is called electrophoresis.
Insulating materials are classified according to their state of aggregation and chemical nature. The first are divided into solid, liquid, gaseous and solidifying. By chemical nature, they are divided into organic, inorganic and organoelement materials.
Electrical conductivity of dielectrics by state of aggregation:
- Electrical conductivity of gases. Gaseous substances have a rather low current conductivity. It can occur in the presence of free charged particles, which appears due to the influence of external and internal, electronic and ionic factors: X-ray and radioactive species, collision of molecules and charged particles, thermal factors.
- Electrical conductivity of a liquid dielectric. Dependence factors: molecular structure, temperature, impurities, the presence of large charges of electrons and ions. The electrical conductivity of liquid dielectrics largely depends on the presence of moisture and impurities. The conductivity of electricity of polar substances is created even with the help of a liquid with dissociated ions. When comparing polar and non-polar liquids,the former have a clear advantage in conductivity. If the liquid is cleaned of impurities, this will contribute to a decrease in its conductive properties. With an increase in the conductivity of a liquid substance and its temperature, a decrease in its viscosity occurs, leading to an increase in the mobility of ions.
- Solid dielectrics. Their electrical conductivity is determined as the movement of charged dielectric particles and impurities. In strong electric current fields, electrical conductivity is detected.
Physical properties of dielectrics
When the resistivity of the material is less than 10-5 Ohmm, they can be attributed to conductors. If more than 108 Ohmm - to dielectrics. There are cases when the resistivity will be many times greater than the resistance of the conductor. In the interval 10-5-108 Ohmm there is a semiconductor. Metal material is an excellent conductor of electric current.
From the entire periodic table, only 25 elements belong to non-metals, and 12 of them, perhaps, will have the properties of a semiconductor. But, of course, in addition to the substances of the table, there are many more alloys, compositions or chemical compounds with the property of a conductor, semiconductor or dielectric. Based on this, it is difficult to draw a certain line between the values of various substances with their resistances. For example, with a reduced temperature factor, a semiconductor will behave like a dielectric.
Application
The use of non-conductive materials is very extensive, as it is one of the most popular gradeselectrical components. It has become quite clear that they can be used thanks to the properties in an active and passive form.
In a passive form, the properties of dielectrics are used for use in electrical insulating material.
In their active form, they are used in ferroelectrics, as well as in materials for emitters of laser technology.
Basic dielectrics
Common species include:
- Glass.
- Rubber.
- Oil.
- Asph alt.
- Porcelain.
- Quartz.
- Air.
- Diamond.
- Clean water.
- Plastic.
What is a liquid dielectric?
Polarization of this type occurs in the electric current field. Liquid non-conductive substances are used in engineering for pouring or impregnating materials. There are 3 classes of liquid dielectrics:
Petroleum oils are low viscosity and mostly non-polar. They are often used in high-voltage equipment: transformer oil, high-voltage water. Transformer oil is a non-polar dielectric. Cable oil has found application in the impregnation of insulating paper wires with a voltage of up to 40 kV, as well as metal-based coatings with a current of more than 120 kV. Transformer oil has a cleaner structure than capacitor oil. This type of dielectric is widely used in production, despite the high cost compared to analog substances and materials.
What is a synthetic dielectric? Currently, it is banned almost everywhere due to its high toxicity, as it is produced on the basis of chlorinated carbon. A liquid dielectric based on organic silicon is safe and environmentally friendly. This type does not cause metal rust and has the properties of low hygroscopicity. There is a liquefied dielectric containing an organofluorine compound that is especially popular for its non-flammability, thermal properties, and oxidative stability.
And the last kind is vegetable oils. They are weakly polar dielectrics, these include flaxseed, castor, tung, hemp. Castor oil is highly heated and is used in paper capacitors. The rest of the oils are evaporated. Evaporation in them is not caused by natural evaporation, but by a chemical reaction called polymerization. Actively used in enamels and paints.
Conclusion
The article discussed in detail what a dielectric is. Various species and their properties have been mentioned. Of course, to understand the subtlety of their characteristics, you will have to study the section of physics about them in more depth.
