What is electrical resistance?

To date, one of the most important characteristics of any material is its electrical resistance. This fact is explained by the unprecedented in the history of mankind of the spread of electric machines, which led to a different look at the properties of surrounding materials of both artificial and natural origin. The concept of "electrical resistance" has become as important as heat capacity, etc. It is applicable absolutely to everything that surrounds us: water, air, metal, even vacuum.

Every modern person should have an idea about this characteristic of materials. The question "what is electrical resistance" can only be answered if the meaning of the term "electric current" is known. With this and begin ...

The material manifestation of energy is the atom. Everything consists of them, grouped together. The present physical model asserts that the atom is like a reduced model of the stellar system. In the center is a nucleus, which includes particles of two types: neutrons and protons. The proton carries an electric positive charge. At different distances from the nucleus, other particles rotate along circular orbits-electrons carrying a negative charge. The number of protons always corresponds to the number of electrons, so the total charge is zero. The more distant from the nucleus is the orbit of the electron (valence), the weaker the force of attraction that keeps it in the structure of the atom.

In a current-generating machine, the magnetic field releases valence electrons from the orbits . Since an "extra" proton remains in the nucleus of the atom that has lost the electron, the attractive force "tears" the other valence electron from the outer orbit of the neighboring atom. The entire structure of the material is attracted to the process. As a result, there appears a motion of charged particles (atoms with a positive charge and free electrons with a negative charge), which is called the electric current.

A material in whose structure the electrons of external orbits can easily leave an atom is called a conductor. Its electrical resistance is small. This is a group of metals. For example, for the production of wires, aluminum and copper are mainly used. According to Ohm's Law, the electrical resistance of a conductor is the ratio of the voltage created by the generator to the strength of the passing current. By the way, resistance is measured in "Ohms".

It is easy to guess that there are materials in which the valence electrons are very small or the atoms are far removed from each other (gas), so their internal structure can not ensure the passage of current. They are called dielectrics and are used to insulate conductive lines in electrical engineering. The electrical resistance in them is very high.

Everyone knows that a wet dielectric starts to conduct an electric current. In the light of this fact, the question of whether there is an electrical resistance of water is of particular interest. The answer to it is contradictory: yes and no. As mentioned earlier, if there is practically no valence electrons in the material, and the structure itself consists more of a void than particles (remember the periodic table and hydrogen with a single electron in orbit), then under normal conditions, conductivity can not exist. This description is ideally suited for water: the combination of two gases, which we call a liquid. Indeed, being completely purified from dissolved impurities, it is a very good dielectric. But since in nature in the water there are always salt solutions, the electric conductivity is provided by them. Its level is affected by the saturation of the solution and the temperature (the aggregate state). That's why an unambiguous answer to the question can not be, because water is different.