Phenomena such as dielectric susceptibility and permittivity are found not only in physics, but also in ordinary life. In this regard, it is necessary to determine the values of these phenomena in science, their influence and application in ordinary life.
Determination of tension
Tension is a vector quantity in physics, which is calculated by the force affecting the unit positive charge located at the studied point of the field. After the dielectric is placed in an external electrostatic field, it acquires a dipole moment, in other words, it becomes polarized. In order to quantitatively describe the polarization in a dielectric, polarization is used - a vector physical indicator calculated as the dipole moment of the dielectric volume value.
The tension vector after passing through the face between two dielectrics undergoes a jump-like change, causing this interference during the calculation of electrostatic fields. In this regard, an additional characteristic is introduced - the electric displacement vector.
Using permittivity, you can find out how many times a dielectric can weaken an external field. For the most rational explanation of electrostatic fields in dielectrics, an electric displacement vector is used.
Key Definitions
The absolute dielectric constant of the medium is a coefficient that is included in the mathematical notation of the Coulomb law and the equation of the relationship of electric field strength and electric induction. The absolute dielectric constant can be represented as the product of a relative indicator of the dielectric constant of the medium and constant electricity.
The dielectric susceptibility, called the polarizability of a substance, is a physical quantity that can polarize under the influence of an electric field. It is also a linear coupling coefficient of an external electric field with the polarization of a dielectric in a small field. The dielectric susceptibility formula is written as follows: X = na .
In most cases, dielectrics have a positive dielectric susceptibility, and this value is dimensionless.
Ferroelectricity is a physical phenomenon present in certain crystals, called ferroelectrics, at certain temperature values. It consists in the appearance of spontaneous polarization in a crystal even without an external electric field. The difference between ferroelectrics and pyroelectrics is that in certain temperature ranges their crystalline modification changes, and random polarization disappears.
Electricians in the field do not behave like conductors, but they have common features. The dielectric differs from the conductor in the absence of free charged carriers. They are present there, but in minimal quantities. In a conductor, an electron that moves freely in the metal crystal lattice will become such a charge carrier. However, electrons in a dielectric are bound to their own atoms and cannot easily move. After dielectrics are introduced into the field with electricity, electrification appears in it, like a conductor. The difference from the dielectric is that the electrons do not move freely throughout the volume, as it flows in a conductor. However, under the influence of an external electric field, a slight displacement of charges arises from the inside of the molecule of the substance: the positive will be displaced in the direction of the field, and the negative will be displaced.
In this regard, the surface acquires a certain charge. The procedure for the appearance of a charge on the surface of a substance under the influence of electric fields is called the polarization of the dielectric. If in a homogeneous and non-polar dielectric with a certain concentration of molecules all the particles are the same, then the polarization will also be the same. And in the case of the dielectric susceptibility of a dielectric, this value will be dimensionless.
Bound Charges
Due to the polarization process, uncompensated charges appear in the volume of the dielectric substance, called polarization or bound. Particles having these charges are present in the charges of molecules and, under the influence of an external electric field, are displaced from the equilibrium position without leaving the molecule in which they are located.
Bound charges are characterized by surface density. The dielectric susceptibility and permeability of the medium determines how many times the binding force of two electric charges in space is less than the same indicator in a vacuum.
The relative air susceptibility and permeability of most of the other gases under standard conditions is close to unity (due to the small plane). The relative dielectric susceptibility and permittivity in ferroelectrics is tens and hundreds of thousands on the separation surface of a pair of dielectrics with different absolute permittivity and susceptibility parameters of the substance, as well as equal tangential components between them.
Among many practical situations, there is a meeting with the transition of a current from a metal body into the surrounding world, while the specific conductivity of the latter is several times less than the conductivity of this body. Similar situations can occur, for example, during the passage of current through metal electrodes buried in the ground. Often use steel electrodes. If the task is to determine the dielectric susceptibility of glass, then the task will be somewhat complicated by the fact that this substance has an ion-relaxation property, due to which a slight delay appears.
At the boundary of a pair of dielectrics with different permittivities in the presence of an external field, polarization charges with different exponents with different surface densities appear. Thus, a new condition is obtained for the refraction of a field line during the transition from an insulator to another.
The law of refraction in the case of streamlines can be considered in its form to be similar to the law of refraction of displacement lines on the boundary of two dielectrics in electrostatic fields.
Each body and substance of the surrounding world has certain electrical properties. The reason for this lies in the molecular and atomic structure - the presence of charged particles, which are in an interconnected or free state.
If the external field does not affect the substance, then such parts are arranged, balancing each other, in the total total volume, without creating additional electric fields. If the application of electric energy occurs outside, inside the existing molecules and atoms there will be a redistribution of charges, which will lead to the appearance of its own internal field, which will be directed towards the external.
When designating the applied external field as E0, and the internal E ', then the entire field E will be the sum of these quantities.
All substances in electricity are usually divided into:
This classification has existed for a long time, but is not entirely accurate, since science has long discovered bodies with new or combined properties of matter.
Conductors
Conducting substances can be media in which free charges are present. Often metals are considered such materials, since their structure implies a constant presence of free electrons capable of moving inside the entire cavity of a substance. The dielectric susceptibility of the medium allows you to be a participant in the thermal process
If the conductor is isolated from the influence of an external electric field, then a balance between positive and negative charges appears inside it. This state immediately disappears when a conductor appears in an electric field, which redistributes charged particles with its energy and provokes the appearance of unbalanced charges with a positive and negative value on the outer surface
This phenomenon is called electrostatic induction. The charges appearing under its action on the metal surface are called induction charges.
The induction charges arising in the conductor create their own field, compensating for the influence of the external field inside the conductor. In this regard, the total total electrostatic field index will be compensated and equal to 0. The potentials of each point inside and outside are equal.
This result indicates that inside the conductor (even with an external field connected) there is no difference in potentials and no electrostatic field. This fact is used in shielding due to the use of the electro-optical protection method for humans and field-sensitive electrical equipment, in particular high-precision measuring instruments and microprocessor technology.
The relationship between permittivity and susceptibility is also there. However, it can be expressed using the formula. So the relationship of dielectric constant and dielectric susceptibility has the following notation: e = 1 + X.
Principle of electrostatic protection
With the help of shielding, clothes and shoes made of materials with conductive properties, including hats, are used in the energy sector for the safety of personnel performing work in conditions of high tension provoked by high-voltage devices. The electrostatic field does not penetrate into the conductor, because when the conductor is introduced into the electric field, it will be compensated by the field, which occurs due to the movement of free charges.
Dielectrics
This name belongs to substances with insulating qualities. Only interconnected charges are in their composition, and not free. Each positive particle in them will be bonded to the negative inside the atom with a common neutral charge without free movement. They are distributed from the inside of dielectrics and cannot change their position under the influence of external fields. In this case, the dielectric susceptibility of the substance and the energy received nevertheless entails certain changes in the structure of the substance. Inside the atom and the molecule, the ratio of the positive and negative charges of the particle changes, and on the surface of the substance extra unbalanced interconnected charges appear, creating an internal electric field. It is directed towards the externally applied tension.
This phenomenon is called the polarization of the dielectric. It can be characterized by the fact that an electric field appears inside the substance, caused by the influence of external energy, but weakened by the reaction of the internal field.
Polarization types
Inside dielectrics, it can be represented by two types:
The first type also has an additional name - dipole polarization. This property is inherent in dielectrics with displaced centers at the positive and negative charge, which create molecules from small dipoles - a neutral collection of a pair of charges. This phenomenon is characteristic of a liquid, hydrogen sulfide, denounced nitrogen.
Without the influence of an external electric field in these substances, molecular dipoles are randomly oriented under the influence of current temperature changes, while on the outside the dielectric does not have an electric charge.
This picture changes under the action of the energy applied from the outside, when the dipoles do not change their own orientation much and uncompensated macroscopic bound charges appear on the surface, creating a field with a counter direction to the field applied from the outside.
Electron polarization, elastic mechanism
This phenomenon occurs in non-polar dielectrics - materials of a different type with molecules in which there is no dipole moment, which under the influence of an external field is deformed so that only positive charges are oriented in the direction of the external field vector, and negative ones - in the opposite direction.
As a result, each molecule functions as an electric dipole oriented along the axis of the applied external field. In a similar way, an own field appears in the opposite direction on the external surface.
Nonpolar Dielectric Polarization
For these substances, a change in the molecules and subsequent polarization from the influence of the field outside is not dependent on their movement under the influence of temperature. Methane CH4 can be used as a nonpolar dielectric. The numerical parameters of the internal field of both dielectrics in magnitude will initially vary in proportion to the change in the external field, and after saturation, nonlinear effects appear. They appear when each molecular dipole is lined up along the lines of force near polar dielectrics or changes in non-polar substances occur due to the strong deformation of atoms and molecules from a large amount of energy applied externally. In practical cases, this is extremely rare.
The dielectric constant
Among the insulating materials, a significant role is given to electrical indicators and such a characteristic as dielectric constant. Both are priced according to two different characteristics:
- absolute value;
- relative indicator.
The term absolute permittivity of a substance is understood as an appeal to the mathematical notation of the Coulomb law. With its help, the relationship between the induction vector and the intensity is described in the form of a coefficient.