A substance having free particles with a charge,moving through the body due to the acting electric field in an orderly manner, is called the conductor in the electrostatic field. And the particle charges are called free. Dielectrics, on the other hand, do not. Conductors and dielectrics have different nature and properties.
In the electrostatic field, conductors - metals, alkaline, acidic and salt solutions, as well as ionized gases. Carriers of free charges in metals are free electrons.
When entering a homogeneous electric field,where the metals are conductors without charge, motion will begin in the direction that is opposite to the field voltage vector. Accumulating on one side, the electrons will create a negative charge, and on the other side an insufficient amount will cause an excess positive charge. It turns out that the charges are divided. Uncompensated different charges arise under the influence of an external field. Thus, they are induced, and the conductor in the electrostatic field remains without charge.
Electrification when charges are redistributedbetween parts of the body, is called electrostatic induction. Uncompensated electric charges form their body, the internal and external stresses are opposite to each other. Separating and then accumulating on opposite parts of the conductor, the intensity of the internal field increases. As a result, it becomes null. Then the charges are balanced.
In this case, the entire uncompensated charge isoutside. This fact is used to obtain electrostatic protection, which protects devices from the influence of fields. They are placed in grids or grounded housings made of metal.
Substances without free electric charges inThe standard conditions (that is, when the temperature is not too high and not low) are called dielectrics. Particles in this case can not move around the body and are displaced only slightly. Therefore, the electric charges are connected here.
Dielectrics are divided into groups independence on the molecular structure. The molecules of the first group of dielectrics are asymmetric. These include ordinary water, and nitrobenzene, and alcohol. Their positive and negative charges do not match. They act as electric dipoles. Such molecules are considered polar. Their electric moment is equal to the final value under all different conditions.
The second group consists of dielectrics, in whichthe molecules have a symmetrical structure. It is paraffin, oxygen, nitrogen. Positive and negative charges in them are of similar importance. If there is no external electric field, then the electric moment is also absent. These are nonpolar molecules.
Different charges in molecules in an external field have biased centers, directed in different directions. They turn into dipoles and get another electrical moment.
Dielectrics of the third group have a crystal structure of ions.
It is interesting how the dipole behaves in an external homogeneous field (in fact it is a molecule consisting of nonpolar and polar dielectrics).
Any charge of a dipole is endowed with power, each ofwhich has the same module, but a different direction (opposite). Two forces are formed, having a rotational moment, under the action of which the dipole tends to rotate in such a way that the direction of the vectors coincides. As a result, he receives the direction of the external field.
In the nonpolar dielectric of the external electricthere is no field. Therefore, the molecules are devoid of electric moments. In a polar insulator, thermal motion is formed in complete disorder. Because of this, the electrical moments have a different direction, and their vector sum is zero. That is, the dielectric does not have an electric moment.
We place the dielectric in a homogeneous electricfield. We already know that dipoles are molecules of polar and nonpolar dielectrics, which are directed depending on the external field. Their vectors are ordered. Then the sum of the vectors is not zero, and the dielectric has an electric moment. Inside it there are positive and negative charges, which are mutually compensated and are close to each other. Therefore, the dielectric does not receive a charge.
Opposite surfaces have uncompensated polarization charges, which are equal, that is, the dielectric is polarized.
If we take an ion dielectric and place it in an electric field, then the crystal lattice of the ions in it will slightly shift. As a result, an ionic dielectric will receive an electrical moment.
Polarization charges form their ownan electric field that has the opposite direction to the outside. Therefore, the intensity of the electrostatic field, which is formed by charges placed in a dielectric, is less than in a vacuum.
A different picture will develop with the conductors.If the conductors of the electric current are introduced into the electrostatic field, a short current will appear in it, since the electric forces acting on the free charges will contribute to the appearance of motion. But also everyone knows the law of thermodynamic irreversibility, when any macroprocess in a closed system and movement must end up in the end, and the system is balanced.
A conductor in an electrostatic field is a body ofmetal, where the electrons begin to move against the lines of force and begin to accumulate on the left. The conductor on the right will lose electrons and receive a positive charge. When the charges are divided, it will find its electric field. This is called electrostatic induction.
Inside the conductor, the strength of the electrostatic field is zero, which is easy to prove by moving from the opposite.
The conductor charge accumulates on the surface. In addition, it is distributed in such a way that the charge density is oriented to the curvature of the surface. Here it will be more than in other places.
Conductors and semiconductors have a curvature greaterall on the points of the corner, edges and rounds. Here, too, a large charge density is observed. Along with its increase, tension is also growing side by side. Therefore, a strong electric field is created here. There is a corona charge, because of what the charges from the conductor flow.
If we consider a conductor in electrostaticA field with an internal part removed, a cavity is revealed. From this nothing will change, because the field as it was not, it will not. After all, in the cavity it is absent by definition.
We examined conductors and dielectrics. Now you can understand their differences and the features of the manifestation of qualities under similar conditions. So, in a homogeneous electric field they behave quite differently.
