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, this phenomenon is based on the fact that charged electrons collide with the atoms that make up the conductor material during their movement.
As the results of numerous studies show, the number of such electron collisions is directly related to the ability of a particular material to pass an electric current through itself with minimal loss. Accordingly, the reaction that the conductor material exerts to the electric current passing through it is called the “electrical resistance of the conductor” in physics .
This resistance is directly dependent on 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 when creating certain materials, it becomes more important not just how actively the conductor resists the passage of electric current through it, but how it is able to conduct this current. The concept opposite to electrical resistance is conductivity.
The 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 quantities equal to m / ohm × mm ^ 2 or in siemens / meter).
In accordance with the basic law of electrical engineering - Ohm's law - the conductivity value shows the relationship between the current density that occurs in a particular conductor and the numerical value of the electric field that appears in a particular medium. However, this position is valid only for a homogeneous medium; in a nonuniform layer, conductivity is nothing but a tensor.
Of metals, the highest conductivity is characteristic of silver and copper. This is primarily due to the structural features of their crystal lattices, which make it possible to relatively easily move charged particles (electrons and ions).
It is natural that pure metals have a higher conductivity than alloys, therefore, in industry, they strive to use the most pure copper with an impurity content of not more than 0.05% for industrial purposes. By the way, the specific conductivity of copper is 58.5 simmens / mm ^ 2, which is significantly higher than that of the vast majority of other metals.
In addition to metal conductors, non-metal conductors are widely used in industry and everyday life, the most common of which is coal. In particular, special brushes for electric machines, electrodes used in searchlights, and others are made from it.