The movement of electric current in conductors is inevitably accompanied by the action of certain physical forces that prevent this movement. From the point of view of the atomic-molecular theory of the structure of matter, this phenomenon is based on the fact that charged electrons during their movement collide with the atoms that make up the material of the conductor.
As the results of numerous studies show, the number of such collisions of electrons is directly related to the ability of a material to pass an electric current through itself with minimal losses. Accordingly, the resistance that the material of the conductor has to the electric current passing through it has received the name "electrical resistance of the conductor" in physics.
Resistance is directly proportional to voltage and inversely proportional to 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 when creating certain materials, it is not how actively the conductor resists passing through it that becomes more importantelectric current, but how much it is able to conduct this very current. The opposite of electrical resistance is conductivity.
Specific electrical conductivity, used in physics, characterizes the general ability of a body to be a conductor of electric current. In quantitative terms, conductivity is the reciprocal of resistivity. It is denoted by the letter γ and is measured in units of m/ohm×mm^2 or siemens/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 occurs in a particular conductor, and the numerical value of the electric field that appears in a particular environment. However, this provision is valid only for a homogeneous medium; in an inhomogeneous layer, the specific conductivity is nothing but a tensor.
Of the metals, the highest specific conductivity is characteristic of silver and copper. This is primarily due to the peculiarities of the structure of their crystal lattices, which make it possible for charged particles (electrons and ions) to move relatively easily.
It is quite natural that pure metals have a higher conductivity than alloys, therefore, in the industry for electrical purposes, they tend to use the purest copper with an impurity content of no more than 0.05%. By the way, the specific conductivity of copper is 58,5 Simmens/mm^2, which is significantly higher than the vast majority of other metals.
In addition to metal conductors, non-metal conductors, the most common of which is coal, are widely used in industry and everyday life. From it, in particular, special brushes for electric machines, electrodes used in searchlights, etc. are made.
