The electricity as a form of energy is essentially linked to the phenomena caused by electrical charges when they are at rest are called electrostatic. The matter is formed by atoms, atoms are formed by the nucleus where protons and neutrals are found, and by the electrosphere composed of orbits where the electrons are rotating.
Among neutrons, protons, and electrons the main difference is in their electrical charges. Neutrons have no charges, protons have positive charges while electrons have negative charges. It is understood that all atoms are at first electrically neutral since the number of protons is equivalent to the number of neutrons, thus the positive charges are annual with the negative charges.
Attraction and repulsion
The principles of electrostatics are based on Dufay’s law, in this principle, called attraction and repulsion, Dufay explains that electrical charges of opposite signals are attracted, while charges if equal signals are repelled. The intensity or modulus of an electric charge, represented by Q, is measured in a unit called Coulomb (C).
For a given body to acquire an electric charge of 1C positive or negative, it is necessary to lose or gain, respectively, an amount of 62.5 × 1018 electrons, which makes us conclude that the electric charge of a single electron is 1 , 6 × 10-19 C.
In the atom, the protons, present in the nucleus, tend to attract electrons towards the nucleus, because they have opposite electrical charges. However, as the electrons rotate in circular orbits around the nucleus, there is also a centrifugal force, which tends to move it away from the nucleus. What happens is a balance between the attraction force and the centrifugal force, which keeps the electron in its orbit.
The distribution of electrons in orbits around the nucleus occurs according to the energy levels that each electron has. The further away an electron is from the nucleus, the greater its energy, but the weaker it is bound to the nucleus.
For the study of electricity, it is interesting to know only the characteristics of the last layer, also called the valence layer. It is in this layer that electrical phenomena occur. In metallic materials, the distribution of electrons in the layers occurs in such a way that there are few electrons in the valence layer. These electrons have a very weak connection with the nucleus, being easily removed from its orbit by an external agent, being called free electrons.
Electrical conductors, insulators and semiconductors.
The electrical conduction in these materials occurs through the movement of these free electrons between nearby atoms. In other materials, the valence layer may be almost complete. In this case, the bonding force of these electrons with the nucleus of the atom is great, causing them to not be easily removed from their orbits, that is, the electrons are not free.
The above statements converge to the conclusion that materials that have free electrons in their constitution are good electrical conductors, with metallic materials standing out in this category, while materials that do not have free electrons are poor conductors of electricity, also called insulators, among the which we can mention plastic, rubber, glass, air, among others.
There is also a third category of materials, called semiconductor materials, whose characteristics make them intermediate between conductors and insulators, which are used in the construction of electronic devices, among which are silicon and germanium.
Conductors are materials whose nature is such that electrical energy can pass easily. All metals and some liquids are conductive, such as salt and acid solutions. The conductive materials most used to transport electricity are copper and aluminum, in the form of wires and cables.
There are other materials, such as rubber, glass, porcelain, plastic, etc., that do not let electrical energy pass and therefore are called insulators. The insulating materials serve precisely to protect the electrical conductors through which electrical energy passes.