Often in the electrical literature there is the concept of " electrical resistivity of copper." And you involuntarily wonder, what is it?
The concept of "resistance" for any conductor is continuously associated with an understanding of the process of electric current flowing through it. Since the article will focus on the resistance of copper, then we should consider its properties and the properties of metals.
When it comes to metals, you involuntarily remember that they all have a certain structure - a crystal lattice. Atoms are located in the nodes of such a lattice and perform periodic oscillations relative to them . The distances and locations of these nodes depend on the forces of interaction of atoms with each other (repulsion and attraction), and are different for different metals. And electrons revolve around atoms in their orbits. They are also held in orbit by a balance of forces. Only this is the force of attraction to the atom and centrifugal. Fancy a picture? You can call it, in some ways, static.
Now add the speakers. An electric field begins to act on a piece of copper. What happens inside the conductor? Electrons, plucked by the strength of the electric field from their orbits, rush to its positive pole. So much for the directional movement of electrons, or rather, electric current. But on the path of their motion, they stumble upon atoms in the nodes of the crystal lattice and electrons still continuing to rotate around their atoms. In doing so, they lose their energy and change direction. Now the meaning of the phrase "resistance of the conductor" is becoming a little clearer? These are lattice atoms and electrons rotating around them that resist the directional movement of electrons plucked from their orbits by an electric field. But the concept of conductor resistance can be called a common characteristic. Each conductor characterizes resistivity more individually. Copper including. This characteristic is individual for each metal, since it directly depends only on the shape and size of the crystal lattice and, to some extent, on temperature. As the temperature of the conductor increases, the atoms make a more intense oscillation at the lattice sites. And electrons revolve around nodes with greater speed and in orbits of a larger radius. And, of course, that free electrons encounter greater resistance when moving. This is the physics of the process.
Copper resistivity is a standard value. The values of this parameter for all metals and other substances measured at 20 ° C can be easily found in the reference table. For copper, it is 0.0175 Ohm * mm2 / m. Of the metals most widely found in nature, this value is close in value only to aluminum. He has it is 0.0271 Ohm * mm2 / m. The resistivity of copper is second only to silver, whose value is 0.016 Ohm * mm2 / m. This leads to its widespread use in electrical equipment, in the manufacture of power cables, various types of conductors, in the printed wiring of electronic devices. Without copper wires, it is impossible to create power transformers and motors for small household electrical appliances with the property of energy conservation. In this case, the requirements for the chemical purity of the substance increase significantly, since in the presence of even 0.02% aluminum in it, the resistivity of copper increases by 10%. Such copper, however, is considered technically pure and a number of certain products can be made from it.
Without knowledge of the resistivity values, it is impossible to calculate the total resistance of conductors by their size and shape when developing and designing electrical equipment. To calculate the total resistance of the conductor, the formula R = p * l / S is used, where the abbreviations encountered indicate the following:
R is the total resistance of the conductor;
p is the resistivity of the metal;
l is the length of the conductor;
S is the cross-sectional area of the conductor.
For the needs of the electrical industry, a wide production of metals such as aluminum and copper has been established, the resistivity of which is quite small. Cables and various types of wires are made from these metals, which are widely used in construction, for the production of household appliances, the manufacture of tires, transformer windings and other electrical products.