What are the types of dielectric polarization and what are the engineering implications of dielectri

Dielectrics can produce the following 3 types of polarization under the action of an external electric field:

Distribution of electron clouds outside the nucleus.

Distortion is generated, resulting in an electric dipole moment that is not equal to zero, which is called distortion polarization;

Molecules with overlapping positive and negative electric centers are separated from each other under the action of an external electric field, which is called displacement polarization.

The original orientation of the molecule with the intrinsic electric dipole moment is chaotic, the sum of the electric dipole moments on the macroscopic level is equal to zero, and under the action of the external electric field, the electric dipoles tend to be arranged in a consistent manner, so that the macroscopic electric dipole moment is not equal to zero, which is called steering polarization.

Extended Materials. Polarization is a phenomenon in which the movement of an electric current eventually causes the potential to deviate from the electrode open circuit potential. When the current is constantly moving, both the cathode and the anode will be polarized.

Polarization reduces the potential difference between the anode and cathode, which reduces the corrosion current and corrosion rate. At first, there are a large number of reactants around the cathode, which can reduce the electrons on the cathode in time.

However, with the increasing cathodic reaction, there are fewer and fewer reactants around the cathode, and more and more products are deposited after the reaction. Because the reaction products cannot be moved quickly, it prevents new reactants from approaching the cathode. The end result is that more and more excess electrons in the cathode region are not digested.

1. Electronic displacement polarization.

All dielectrics are made up of molecules, which in turn are made up of atoms, and each atom is made up of a positively charged nucleus and negatively charged electrons surrounding the nucleus.

2. Ionic polarization.

The polarization of ions was first proposed by Fajans. Ion polarization refers to the phenomenon that the electron clouds of positive and negative ions are deformed under the action of the electric field of the opposing ions in ionic compounds. Ionic polarization energy has an effect on the properties of metal compounds.

3. Dipole polarization.

Dipole polarization means that under the action of the electric field, the intrinsic dipole moments of the molecules that make up the medium will be arranged along the direction of the electric field, and the vector sum of all dipole moments is not zero, and the medium produces macroscopic polarization intensity.

4. Space charge polarization.

Space charge polarization often occurs in an inhomogeneous medium, under the action of an external electric field, the positive and negative gap ions in the inhomogeneous dielectric move to the negative and positive electrodes respectively, causing a change in the ion density at each point in the dielectric and producing an electric dipole moment, which is called space charge polarization.

5. Sandwich polarization.

Sandwich polarization is a special type of space charge polarization that occurs in composite insulation composed of multiple dielectrics.

Under the action of an external electric field, dielectric.

Shows the phenomenon of electrical properties. There is no free charge inside the ideal insulating medium, and there is always a small amount of free charge inside the actual dielectric, which is the cause of dielectric leakage. In general, the positive and negative bound charges inside a dielectric that is not acted upon by an electric field are canceled out on average, and the electrical properties are not shown macroscopically.

Under the action of an external electric field, the local movement of the bound charge leads to the macroscopic display of electrical properties, the appearance of a charge on the surface of the dielectric and in the internal unevenness, this phenomenon is called polarization, and the charge that appears is called polarization. These polarized charges change the original electric field. A capacitor filled with a dielectric has a larger capacitance than a vacuum capacitor due to the polarization of the dielectric.

Think of the dielectric as a charge system composed of a large number of microscopic charged particles, from electromagnetism.

Based on the basic formula, using vector analysis and the relevant formulas of electrodynamics, the electric potential generated by a single atom somewhere in space is equivalent to the potential of an electric dipole is obtained through quantitative calculation, and the existence of the intrinsic moment of molecules or atoms, the classification of dielectric molecules, the polarization model of dielectric in the external electric field and the law of dielectric polarization are explained from the theoretical level.

Electron polarization, which is the nucleus of an atom under the action of an electric field.

with a negative electron cloud.

between relative displacements, their equivalent centers no longer coincide and are separated by a certain distance l to form an electric dipole moment pe=el (l from the negative center to the positive center, e is the amount of charge.

See electric dipoles). When the electric field is not too strong, the electric dipole moment pe is proportional to the effective electric field, pe = ee, where e is called the electron polarizability.

Ion polarization, also known as atomic polarization, is the displacement of heteropolar ions in the opposite direction along the electric field in a substance composed of positive and negative ions to form an electric dipole moment proportional to the effective electric field, Pa = ae, a is called ion polarizability, both polarizations are independent of temperature.

The dipole turns to polarization, and some dielectric molecules have an intrinsic polar moment p due to structural asymmetry. In the absence of an external electric field, the orientation of these molecules is completely random due to thermal motion, and the dielectric does not show electrical properties macroscopically. Under the action of the external electric field, the electric moment of each molecule is affected by the moment of the electric field bending and tends to be parallel to the external field, that is, it tends to be ordered. On the other hand, thermal motion causes the electric moment to tend to be disordered.

At a certain temperature and a certain external electric field, the two reach equilibrium. The orientation polarization of the intrinsic moment can also be described by the orientation polarizability d when the electric field strength.

When it is not too large and the temperature is not too low, , k is the Boltzmann constant.

t is the thermodynamic temperature.

This polarization is closely related to temperature.

Due to the inhomogeneity of the dielectric components and other incompleteness, such as the presence of impurities and defects, a small amount of free charge in the dielectric stays in the trapping center or the uneven interface of the dielectric and cannot be neutralized with each other, forming a space charge layer, thereby changing the electric field of the space. In effect, it is equivalent to enhancing the dielectric strip performance of the dielectric.

The polarization of the dielectric is the macroscopic total effect of these four polarization mechanisms.

Factors affecting electrolyte polarization: electric field strength; mains frequency; Temperature (the low temperature section increases with temperature and decreases when the temperature is high).

1.Electron displacement polarizationUnder the action of an external electric field, the electron orbitals on the periphery of the atom are displaced relative to the nucleus, and the center of gravity of the positive and negative charges in the atom is relatively displaced. This polarization is called electron-displacement polarization (also known as electron-deformation polarization).

2.Ion displacement polarizes the movement of the ion to offset the equilibrium position under the action of the electric field, which is equivalent to the formation of an induced dipole moment; It can also be understood as the elongation of the bonds between ions under the action of an electric field in ionic crystals, as is the case with alkali halide crystals. According to the classical theory of elastic vibration, the ionic displacement polarizability can be estimated.

3.When there are weakly connected electrons, ions, dipoles and other relaxation particles in the material, the thermal motion caused by temperature makes the distribution of these particles chaotic, while the electric field causes them to be distributed in an orderly manner, and the polarization state is established in equilibrium. This polarization is statistical in nature and is called thermal relaxation (relaxation) polarization.

The distance of movement of the charged particles caused by polarization can be comparable to the size of the molecule, or even larger.

Polarization of Dieletries Under the action of an external electric field, an induced electric dipole moment is generated inside the dielectric along the direction of the electric field, and a bound charge appears on the surface of the dielectric. According to the microscopic mechanism of polarization, dielectric polarization can be summarized into four basic forms: (1) Under the action of an external electric field, the electron cloud around the nucleus of the electron cloud in the dielectric constituent particles (atoms, ions, or molecules) produces an induced electric dipole moment.

Since the mass difference between the two is very large, and the main displacement is done by the electron, this polarization is called the electron displacement polarization port. (2) Under the action of the external electric field, the relative elastic displacement between the atoms (or alien reeds) that make up the molecule produces an induced electric dipole moment, which is called atomic (or orange mountain ion) displacement polarization. (3) Under the action of the external electric field, the intrinsic electric dipole moment of the dielectric polar molecule is turned along the direction of the electric field to produce a macroscopic induced electric dipole moment, which is called steering polarization.

4) The movement of the conductive carriers in the dielectric under the action of the electric field may be captured by defects in the medium or the interface of different media, resulting in an uneven distribution of charges in the dielectric and the generation of macroscopic induced electric dipole moments, which is called space charge polarization or sandwich polarization.

The conductor ball will shout to reach electrostatic equilibrium, and the internal field strength of the conductor ball is zero everywhere.

The dielectric ball is different from the conductor ball, and there is no free-moving charge inside the beam slag, and the internal field strength of the dielectric ball can be infiltrated quietly under the external field strength, which will produce the phenomenon of polarization.

Dielectric:The charged particles of the dielectric are tightly bound by the internal or intermolecular forces of atoms and molecules, and under the action of the external electric field, these charges can only move in the microscopic range, resulting in polarization.

In an electrostatic field, an electric field can be present inside the dielectric, which is the basic difference between a dielectric and a conductor.

Dielectrics come in gas, solid, and liquid forms, and dielectric materials are used as insulating materials in electrical equipment. All dielectrics exhibit electrophysical phenomena such as polarization, conductivity, and loss under the action of an electric field.

The polarization of the dielectric is the elastic displacement of the charge that binds the lead and the steering displacement of the dipole produced by the electric field of the dielectric, which is called the polarization of the dielectric.

Effect: Weakens the external electric field and increases the equivalent capacitance of the dielectric.

Simply put, there is no electric field, and the positive and negative charges are mixed together in a disorderly manner, that is, the rice and millet are mixed in a bag and stirred evenly, and after a uniform electric field, the positive and negative charges are polarized and separated, and the positive charges are gathered in the direction of the electric field, and the negative charges are gathered in the opposite direction, just like the mixed rice and millet in this bag are separated and gathered on both sides.