As you know, characteristic of conductors is, they always have a large number of mobile charge carriers, t. e. free electrons or ions.

Inside the conductor, these charge carriers, generally speaking, move randomly. However, if the conductor has an electric field, on chaotic motion of the carriers imposed their orderly movement in the direction of the action of electric forces. This directional movement of mobile charge carriers in the conductor in the field is it always like this, that the field inside the conductor is attenuated. Since the number of mobile charge carriers in the conductor is great (in 1 cm³ metal contains about 10²² free electrons), their movement under the action of the field going as long, while the field inside the conductor will not disappear altogether. Find out more, as it happens.

Let a metallic conductor, consisting of two tightly pressed to each other parts, placed in an external electric field E (rice. 15.13). For free electrons in the conductor, there is the force field F₁, directed to the left, t. e. opposite to the electric field vector. As a result of displacement of electrons under the action of these forces on the right end of the conductor occurs an excess of positive charges, and on the left is an excess of electrons. Therefore, between the ends of the conductor there is an internal field (field offset charges), which on rice. 15.13 depicted in dashed lines. Inside the conductor this field is directed towards the outside and on each remaining within the conductor free electron acts with the force F₂) pointing to the right.

First force F₁ more power F₂ and their resultant is directed to the left. Therefore, the electrons inside the conductor continues to shift to the left, and inner margin is gradually strengthening. When the left end of the conductor will accumulate a lot of free electrons (they are still a tiny fraction of their total number), power F₂ equal to the force F₁ and their resultant will be zero. After that, remaining inside the conductor the free electrons will move randomly only. This means, the field strength inside the conductor is zero, t. e. that the field inside the conductor has vanished.

So, when the conductor enters the electric field, he so electrified, on one end occurs a positive charge, and another — same magnitude negative charge. Such static charges is called electrostatic induction or static effect. Note, in this case, redistributed, only the charges of a conductor. So, if such a conductor be removed from field, its positive and negative charges are again uniformly distributed throughout the volume of the conductor and all of it will be electrically neutral.

It is easy to verify, on the opposite ends of the conductor, electrified by influence, truly, there are an equal number of charges of opposite sign. Divide this guide into two parts (rice. 15.13) and then remove them from the field. Combining each part of the conductor with separate the electroscope, we make sure, they are charged with. If you re-join the two parts so, so they were single conductor, we find, what charges are neutralized. So, to connection the charges on both parts of the conductor are equal in magnitude and opposite in sign.

Time, in the course of which the electrification of the conductor influence, so little, the balance of charges on the conductor occurs almost instantly. Tensions, so, and the potential difference inside the conductor everywhere be equal to zero. Then for any two points inside a conductor is true, the ratio:

ϕ₁‒ϕ₂=0, ie. ϕ₁=ϕ₂

Therefore, when the balance of charges on the conductor the potential of all its points the same. This also applies to the conductor, electrified by contact with a charged body. Take a conducting sphere and place the point M on the surface of the charge q (rice. 15.14). Then in Windows Explorer for a short time there is a field of, while at the point M is the excess charge. Under the influence of this field the charge is evenly distributed over the entire surface of the ball, which leads to the disappearance of the field inside the conductor.

So, regardless, how electrified conductor, in equilibrium of charges inside the conductor the field is not, and the potential of all points of a conductor are the same (inside, and on the surface of the conductor). At the same time outside an electrified conductor, of course, there is, and the line tension normal (perpendicular) to the surface of the conductor. It is clear from the following reasoning. If the line tension was ever inclined to the surface of the conductor (rice. 15.15), the force F, acting on a charge e at this point the surface, could be decomposed into components F₁ and F₂. Then under the action of force F₂, directed along the surface, the charges would move along the surface of the conductor, what if the balance of charges should not be. Therefore, when the balance of charges on the conductor surface is equipotential surface.

If the field inside a charged conductor is missing, volumetric density of charges in it (the quantity of electricity per unit volume) everywhere should be equal to zero. Indeed, if in any small volume) the conductor was charge q, it is around this volume would exist an electric field.

In field theory proven, what at equilibrium, all excess charge of an electrified conductor is on its surface. This means, all the interior of this conductor can be removed at the location of charges on the surface nothing will change. For example, if equally to electrify two equal-size solitary metal ball, one of which is solid, and the other hollow, the field around the balls will be the same. To experience it for the first time proved M. Faraday.

So, if a hollow conductor placed in an electric field or to electrify by contact with a charged body, when the equilibrium of the charges field inside the cavity will not exist. This is based on electrostatic protection. If any instrument be placed in a metal case, the external electric field to penetrate into the case will not be, t. e. the work and testimony of such a device will depend on the availability and changes of external electric fields.

Find out now, how are the charges on the outer surface of the conductor. Take a metal grid on two insulating handles, to which the glued paper leaves (rice. 15.16). If you charge the net and then stretch it (rice. 15.16, and), the leaves on both sides of the grids will differ. If Flex mesh ring, we only deviate the leaves from the outside of the grid (rice. 15.16, b). Giving the grid a different bend, you can see, that the charges are located only on the convex side of the surface, and in those places, where the surface is more curved (smaller the radius of curvature), accumulates more charges.

So, the only charge is distributed uniformly on the conductor surface of the spherical shape. For an arbitrary shape conductor surface density of charge σ, so, and the field strength near the surface of the conductor over there, more where the curvature of the surface. Especially high charge density on the protrusions and on edges of the conductor (rice. 15.17). You can verify this, touching the probe to various points on the electrified conductor, and then the electroscope. Electrified conductor, having or provided with a blunt tip, quickly loses its charge. Therefore, the conductor, on which charge you want to save for a long time, must not have pointed.