102. Electrical conductivity of various substances

Substances can be classified according to their various properties. For example, the ability to maintain volume and shape is divided into gaseous, liquid and solid substances.

When studying the passage of electric current through different substances, they are classified according to the nature of their electrical conductivity. This results in the division of substances into conductors and dielectrics (or insulators). There are charged particles in conductors which, under the action of an electric field, can move inside the conductor and thus generate electric current. In contrast, in a dielectric, the electric field does not generate current; this shows that there are no charged particles that can move through the substance.

The division of substances into conductors and insulators is largely conventional. In nature, there are no ideal insulators. Even the best known insulators have some, small number of free charged particles compared to conductors.

Among the best insulators are amber, porcelain, glass, ebonite, paraffin, kerosene. The best conductors are metals, and among them silver and copper. Electrolytes can also be good conductors, and ionized gas, which is plasma.

However, the vast majority of substances by their ability to conduct electric current forms an intermediate group. These substances do not conduct electricity well enough to be called conductors, nor are they bad enough to be classified as insulators. So they are called semiconductors.

Semiconductors didn't play any noticeable practical role in the early development of radio electronics. In electrical and radio engineering, only different conductors and insulators were used.

The situation has changed significantly, we can even say that there was a revolution in radio engineering, when the possibility of controlling the electrical conductivity of semiconductors was discovered and studied.

It goes without saying that conductors are still used to transmit electrical energy over wires. Semiconductors, on the other hand, are used as the elements that convert electrical current in radio receivers and transmitters, computers, robots, and other electronic devices.