Different bodies are divided intononconductors (dielectrics) and conductors by 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 the conductors have specialelectric charges. Thus, metals, for example, 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 an electric field ABCD, which is placed in a homogeneous field, with a strain directed from left to right.
On the surface of the conductor AC there is an excessivenegative charge, and excessive positive - 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 weaken. Charges that have conductors in an electric field will stop moving when the intensity of the resultant field inside them becomes zero.
Thus, when the charges on the conductor are in equilibrium, the fieldinside it is missing. Its absence can be used to protect bodies from the influence of an external electric field. For this purpose, it is sufficient to surround the body with a thin conducting layer, for example, place it in a box of metal. There will be no field inside this drawer.
To prove the fact that in a chargedconductor there is no electric field, in his experience, Faraday built a large wire cage, which he installed on the insulators and recharged. Being inside this cell with a supersensitive electroscope, Faraday proved that inside it there are no electrical forces, although a very significant charge was concentrated on the outer surface. This 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 at the contact of such bodies.
When the electrified body is brought closer to the lungconductor, then on it appear the inducted charges of both signs. Thus, charges of opposite signs will be attracted to the body, and charges of the same name will be repelled. Due to the fact that 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 portion 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 in our experience.
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.
