A conductor in an electrostatic field. Conductors, semiconductors, dielectrics

A substance having free particles with a charge moving along the body due to the acting electric field in an ordered manner is called a conductor in an electrostatic field. And the particle charges are called free. Dielectrics, on the other hand, do not. Conductors and dielectrics have different nature and properties.

Conductor

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 metals are conductors without charge, motion will begin in a 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.

Uncompensated charges

Electrification, when charges are redistributed between 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 is located outside. This fact is used to get electrostatic protection, which protects devices from the influence of fields. They are placed in grids or grounded housings made of metal.

Dielectrics

Substances without free electric charges under 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 depending 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 which the molecules have a symmetrical structure. It is paraffin, oxygen, nitrogen. Positive and negative charges in them have a similar meaning. 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 crystalline 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 a force, each of which 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.

There is no external electric field in the nonpolar dielectric. Therefore, the molecules are devoid of electrical 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.

Dielectric in a homogeneous electric field

We place the dielectric in a homogeneous electric field. We already know that dipoles are molecules of polar and nonpolar dielectrics that 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 own electric field, which has the opposite direction to the external one. Therefore, the intensity of the electrostatic field, which is formed by charges placed in a dielectric, is less than in a vacuum.

Conductor

A different picture will develop with the conductors. If the conductors of the electric current are introduced into the electrostatic field, a short-time current will appear in it, since the electric forces acting on the free charges will contribute to the appearance of motion. But also the law of thermodynamic irreversibility is known to everyone, when any macro process in a closed system and movement must end up in the end, and the system is balanced.

The conductor in the electrostatic field is a body of metal, where the electrons start moving against the lines of force and begin to accumulate on the left. The conductor to the right will lose electrons and receive a positive charge. With the separation of charges, it will find its electric field. This is called electrostatic induction.

Inside the conductor, the electrostatic field strength is zero, which is easy to prove by moving from the reverse.

Features of charge behavior

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 curvature most at the points of the angle, edges and roundings. 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. A corona charge appears, which causes charges from the conductor to flow.

If we consider a conductor in an electrostatic field, which has 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.

Conclusion

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.