Specific conductivity as the most important characteristic of conductors of electric current

The movement of electric current in conductors is inevitably accompanied by the action of certain physical forces that impede this movement. From the point of view of the atomic-molecular theory of the structure of matter, the basis of this phenomenon lies in the fact that charged electrons collide with the atoms that make up the material of the conductor during their movement.

As the results of numerous studies show, the number of such electron collisions is directly related to the ability of a material to pass an electric current through itself with minimal losses. Accordingly, the counteraction exerted by the material of the conductor through the electric current passing through it, was called in physics the "electrical resistance of the conductor."

The resistance is in direct proportion to the voltage and inversely proportional to the current strength. In accordance with the international system of units of measurement, it is denoted by the letter R and is measured in Ohms.

At the same time, often with the creation of certain materials, the importance is not so much how actively the conductor resists the passage of an electric current through it, but how much it is capable of carrying this current. The concept, the reverse of the electrical resistance, is the conductivity.

Specific electric conductivity, used in physics, characterizes the general ability of a body to be a conductor of an electric current. Quantitatively, the conductivity is the reciprocal of the resistivity. It is denoted by the letter γ and is measured in terms of m / ohm mm2 or in simens / meter.

In accordance with the basic law of electrical engineering - Ohm's law - the value of specific conductivity shows the interdependence between the current density that arises in a particular conductor and the numerical value of the electric field that appears in this or that medium. However, this position is valid only for a homogeneous medium, in a nonuniform layer the specific conductivity is nothing else than a tensor.

Of metals, the highest specific conductivity is characteristic for silver and copper. This is due primarily to the structural features of their crystal lattices, which make it possible to move relatively easily to charged particles (electrons and ions).

It is quite natural that pure metals have a higher conductivity than alloys, therefore, in industry, for electrical purposes, they try to use the maximum pure copper with an admixture fraction of not more than 0.05%. By the way, the conductivity of copper is 58.5 symmetry / mm ^ 2, which is much higher than the vast majority of other metals.

In addition to metallic conductors, conductors from non-metals, the most common of which is coal, have found wide application in industry and everyday life. From it, in particular, special brushes are made for electric machines, electrodes used in searchlights, etc.