movement of electric current in the conductors is inevitably accompanied by the action of certain physical forces that hinder this movement.From the point of view of atomic and molecular structure of the substance theory behind this phenomenon is that the charged electrons during their movement collide with atoms of which consists of the conductor material.
As the results of numerous studies, the number of such collisions of electrons is directly related to the ability of a material to pass through an electric current with minimum losses.Accordingly, the resistance that a material has a conductor passing through it an electric current received physics called "electric resistance of the conductor."
resistance it is in direct proportion to the voltage and inversely proportional to the current.In accordance with the international system of units it is indicated by the letter R and is measured in ohms.
At the same time, often with the creation of certain materials become increasingly important not how actively resists the passage of a conductor of electric current through it, and the extent to which it is able to carry out this very current.The term inverse electrical resistance is conductivity.
Specific electrical conductivity, applied physics, describes the overall ability of a body is a conductor of electric current.In quantitative terms, the conductivity is the reciprocal of resistivity.It is denoted by the letter γ is measured in an amount equal to M / OD × mm ^ 2 or siemens / meter).
In accordance with the basic law of electrical engineering - Ohm's law - the value of conductivity shows the relationship between the current density that occurs in a given 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 a non-uniform conductivity of the layer is nothing but as a tensor.
From the highest conductivity of metals is characteristic of silver and copper.This is due primarily to the structural features of the crystal lattice, which allow relatively easy to move charged particles (electrons and ions).
Naturally, the pure metals have a higher conductivity than the alloy, so the electrical industry in order to try to use the most pure copper with a share of impurities not more than 0.05%.Incidentally, the conductivity of copper is 58.5 Simmons / mm ^ 2, much higher than the majority of other metals.
addition to metallic conductors in industry and everyday life have found wide application of non-metallic conductors, the most common of which is coal.From it, in particular, make special brushes for electric cars, the electrodes used in projectors and others.
