Conductors in an electric field

Different bodies are divided into non-conductors (dielectrics) and conductors according to their electrical properties. One of the features that conductors have in an electric field is that when charges are in equilibrium on their surface, there will be no electric field inside them. How can I explain this?

The thing is that conductors have special electrical charges. Thus, for example, metals are carriers of charges such as electrons that have lost contact with atoms. They are called free electrons.

Such electrons in a metal conductor placed in an electric field under the influence of the forces of this field will move in a direction that will be opposite to the strength of the electric field.

We take a conductor in the electric field ABCD, which is placed in a homogeneous field, with a strain directed from left to right.

An excessive negative charge arises on the surface of the conductor AC, and an excessive positive one on the other DB. In this example, we see that the conductors in the electric field are electrified. Charges that appear on the surface of the conductor create an additional electric field inside it. Its lines of force have the opposite direction with respect to the lines of force of the main field. As a result, the strength of the main field in the conductor will decrease, i.e. The force that acts on free electrons, and also causes their movement will be weakened. Charges that have conductors in an electric field will stop moving when the intensity of the resultant field inside them becomes zero.

Thus, in the equilibrium of charges on a conductor, the field inside it is absent. Its absence can be used to protect bodies from the influence of an external electric field. To this end, it is sufficient to surround the body with a thin conducting layer, for example, place it in a metal box. There will be no field inside this drawer.

To prove the fact that there is no electric field in the charged conductor, in his experience, Faraday built a large wire cage, which he placed on insulators and recharged. Being inside this cell with a supersensitive electroscope, Faraday proved that inside it there are no electric forces, although a very significant charge was concentrated on the outer surface. Such a phenomenon is called electrization through influence or electrostatic induction. Its cause is the effect of an external electric field on unoccupied electrons in a conductor. And charges that have conductors in an electric field are called inducted charges.

The phenomenon of electrification through influence explains the attraction between electrified and non-electrified bodies, as well as the transfer of electric charge upon contact of such bodies.

When an electrified body is approached to an easy conductor, then inducted charges of both signs appear on it. Thus, charges of opposite signs will be attracted to the body, and charges of the same name will be repelled. Because the charges of the same name are on the side of a light conductor farther from the body, the resultant of these two forces is the force of attraction. Under the influence of this force, an easy conductor will be attracted to the body. At the time of contact, their inducted charge of the opposite sign will be neutralized by a part of the inductive charge, which is equal in magnitude to it. On a light conductor, the same charge will remain the same as on the body.

Because the light conductor now has the same charge as the body, it will push away from it; This is what we observe experimentally.

Conductors and dielectrics in an electric field have different properties. Thus, dielectrics have practically no free charges. When they are placed in an electric field, a phenomenon of polarization occurs.