Today, 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 proliferation of electric machines, which made us take a different look at the properties of the surrounding materials of both artificial and natural origin. The concept of "electrical resistance" has become as important as heat capacity, etc. It applies 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 be answered only if the meaning of the term “electric current” is known. Let's start from this ...
The material manifestation of energy is an atom. Everything consists of them connected in groups. The current physical model claims that the atom is like a reduced model of a stellar system. In the center is the 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 in circular orbits - electrons that carry a negative charge. The number of protons always corresponds to the number of electrons, so the total charge is zero. The farther away from the nucleus is the orbit of the electron (valence), the weaker the attractive force that holds it in the structure of the atom.
In a current-generating machine, a magnetic field releases valence electrons from orbits . Since the “extra” proton remains in the nucleus of an atom that has lost an electron, the attractive force “tears” another valence electron from the outer orbit of the neighboring atom. The whole structure of the material is drawn into the process. As a result, the movement of charged particles (atoms with a positive charge and free electrons with a negative one) appears, which is called an electric current.
A material in whose structure the electrons of the outer orbits can easily leave an atom is called a conductor. Its electrical resistance is small. This is a group of metals. For example, aluminum and copper are mainly used for wire production. According to Ohm's law, the electrical resistance of a conductor is the ratio of the voltage generated 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 there are very few valence electrons or atoms are far removed from each other (gas), so their internal structure cannot ensure the passage of current. They are called dielectrics and are used to isolate conductive lines in electrical engineering. The electrical resistance in them is very high.
Everyone knows that a wet dielectric begins to conduct an electric current. In light of this fact, the question “is there an electrical resistance of water” is of particular interest. The answer to it is contradictory: yes and no. As mentioned earlier, if there are practically no valence electrons in the material, and the structure itself consists of more emptiness than particles (recall the periodic table and hydrogen with a single electron in orbit), then under ordinary conditions, conductivity cannot exist. Water is ideal for this description: 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 salt solutions are always present in nature in water, the electrical conductivity is provided by them. Its level is affected by the saturation of the solution and temperature (state of aggregation). That is why there can be no definite answer to the question, because water can be different.