All bodies are composed of indivisible tiny particles called elementary. They have mass and are able to attract each other. According to the law of universal gravitation, with increasing distance between particles , the attractive force decreases relatively slowly (it is inversely proportional to the square of the distance). The force of interaction of particles exceeds the force of gravity. This interaction is called the "electric charge", and the particles are charged.
Particle interaction is called electromagnetic. It is characteristic of most elementary particles. If it is not between them, then they say that there is no charge.
An electric charge determines the degree of intensity of electromagnetic interaction. It is the most important characteristic of elementary particles, which determines their behavior. It is designated by the letters "q" or "Q".
There is no macroscopic standard for an electric charge unit, since it is not possible to create it because of its inevitable leakage. In atomic physics, the charge of an electron is taken as a unit. In the International System of Units, it is set using current strength. A charge of 1 pendant (1 C) means that it passes at a current strength of 1 A in 1 s through the cross section of the conductor. This is a fairly high charge. It is impossible to tell a small body. But in a neutral conductor to set in motion a charge of 1 C is quite realistic.
An electric charge is a scalar physical quantity that characterizes the ability of particles or bodies to enter into electromagnetic force interaction with each other.
When studying the interaction, the idea of a point charge is important. It is a charged body, the dimensions of which are much smaller than the distance from it to the point of observation or other charged particles. In the interaction of two point charges, the distance between them is much larger than their linear dimensions.
Particles have opposite charges: protons - positive, electrons - negative. These signs (plus and minus) reflect the ability of particles to attract (with different signs) and repel (with one). In nature, positive and negative indicators are offset among themselves.
The electric charge of the particles is the same in absolute value, regardless of whether it is positive, like a proton, or negative, like an electron. The minimum charge is called elemental. All charged particles possess it. It is impossible to separate part of the particle charge. The minimum value is determined experimentally.
Electric charge and its properties can be measured using an electrometer. It consists of an arrow rotating around a horizontal axis and a metal rod. If you touch the rod with a positively charged stick, the arrow will deviate by a certain angle. This is due to the charge distribution along the arrow and the rod. The rotation of the arrow is due to the action of the repulsive force. With increasing charge, the angle of deviation from the vertical also increases. That is, it shows the value of the charge that is transmitted to the rod of the electrometer.
The following properties of an electric charge are distinguished. They can be positive and negative (the choice of names is random), which attract and repel. Charges are capable of being transferred upon contact from one body to another. One body in different conditions can have different charges. An important property is discreteness, which means the existence of the smallest, universal charge, to which the similar indices of any bodies are multiple. Inside a closed system, the algebraic sum of all charges remains constant. In nature, charges of the same sign do not arise and do not disappear simultaneously.