Electrostatics studies the properties and interactions of charges that are stationary in the reference frame in which they are considered.
In nature, there are only two types of electric charges - negative and positive. A positive charge can occur on a glass rod rubbed with skin, and a negative charge can occur on amber rubbed with a woolen cloth.
We know that all bodies are made up of atoms. In turn, an atom consists of a positively charged nucleus and electrons that revolve around it. Since the electrons have a negative charge and the nucleus is positive, the atom as a whole is electrically neutral. When exposed to it from the outside, it can lose one or more electrons and turn into a positively charged ion. In the event that an atom (or molecule) attaches an additional electron to itself, it will turn into a negative ion.
Thus, electric charge can exist in the form of negative or positive ions and electrons. There is one kind of "free electricity" - negative electrons. Therefore, if a body has a positive charge, it does not have enough electrons, and if it has a negative charge, then it has an excess.
The electrical properties of any substance are determined by its atomic structure. Atoms can lose even a few electrons, in which case they are called multiply ionized. The nucleus of an atom is made up of protons and neutrons. Each proton carries a charge that is equal to that of the electron, but opposite in sign. Neutrons are electrically neutral particles (have no electrical charge).
In addition to protons and electrons, other elementary particles also have an electric charge. Electric charge is an integral part of elementary particles.
The smallest charge is considered to be the charge equal to the charge of the electron. It is also called the elementary charge, which is equal to 1.6 10 -19 C. Any charge is a multiple of an integer number of electron charges. Therefore, the electrification of the body cannot occur continuously, but only in steps (discretely), by the value of the electron charge.
If a positively charged body begins to be recharged (charged with negative electricity), then its charge will not change instantly, but will first decrease to zero, and only then acquire a negative potential. From this we can conclude that they compensate each other. This fact led scientists to the conclusion that in "uncharged" bodies there are always charges of positive and negative signs, which are contained in such quantities that their action completely compensates for each other.
When electrified by friction, the negative and positive "elements" contained in the "uncharged body" are separated. As a result of the movement of the negative elements of the body (electrons), both bodies are electrified, and one of them is negative, and the second is positive. The amount of "flow" from one element to another charges remains constant throughout the entire process.
From this it can be concluded that charges are not are created and do not disappear, but only “flow” from one body to another or move inside it. This is the essence of the law of conservation of electric charges. During friction, many materials are subject to electrification - ebonite, glass and many others. In many industries (textile, paper and others), the presence of static electricity is a serious engineering problem, since the electrification of elements caused by the friction of paper, fabric or other production products on machine parts can cause fires and explosions.
The law of conservation of charge can be formulated more briefly - in an isolated system, the algebraic sum of charged elements remains constant:
This law is also valid for the mutual transformations of various elementary particles that make up the atom and the nucleus as a whole.
Leads to the fact that the law of conservation of charge has local character: the change in charge in any predetermined volume is equal to the flow of charge through its boundary. In the original formulation, the following process would be possible: the charge disappears at one point in space and instantly arises at another. However, such a process would be relativistically non-invariant: due to the relativity of simultaneity, in some frames of reference, the charge would appear in a new place before it disappeared in the previous one, and in some, the charge would appear in a new place some time after disappearing in the previous one. That is, there would be a length of time during which the charge is not conserved. The requirement of locality allows us to write down the law of conservation of charge in differential and integral form.
The law of conservation of charge in integral form
Recall that the electric charge flux density is simply the current density. The fact that the change in charge in the volume is equal to the total current through the surface can be written in mathematical form:
Here Ω is some arbitrary region in three-dimensional space, is the boundary of this region, ρ is the charge density, is the current density (flux density of electric charge) through the boundary.
The law of conservation of charge in differential form
Passing to an infinitesimal volume and using the Stokes theorem as necessary, we can rewrite the law of conservation of charge in a local differential form (continuity equation)
Law of conservation of charge in electronics
Kirchhoff's rules for currents follow directly from the law of conservation of charge. The combination of conductors and radio-electronic components is represented as an open system. The total influx of charges into a given system is equal to the total output of charges from the system. Kirchhoff's rules assume that an electronic system cannot significantly change its total charge.
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See what the "Law of Conservation of Electric Charge" is in other dictionaries:
LAW OF CONSERVATION OF ELECTRIC CHARGE- one of the basic laws of nature, consisting in the fact that the algebraic sum of electric charges of any closed (electrically isolated) system remains unchanged, no matter what processes take place inside this system ... Great Polytechnic Encyclopedia
law of conservation of electric charge
Law of conservation of charge- the law of conservation of electric charge - the law according to which the algebraic sum of electric charges of all particles of an isolated system does not change during the processes occurring in it. The electric charge of any particle or system of particles ... ... Concepts of modern natural science. Glossary of basic terms
Conservation laws are fundamental physical laws, according to which, under certain conditions, some measurable physical quantities that characterize a closed physical system do not change over time. Some of the laws ... ... Wikipedia
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The law of conservation of electric charge states that the algebraic sum of the charges of an electrically closed system is conserved. The law of conservation of charge is absolutely true. At the moment, its origin is explained as a consequence of the principle ... ... Wikipedia
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When electrifying bodies, law of conservation of electric charge. This law is valid for a closed system. In a closed system, the algebraic sum of the charges of all particles remains unchanged . If the particle charges are denoted by q 1 , q 2 etc., then
q 1 + q 2 + q 3 + … + q n= const.
The basic law of electrostatics is Coulomb's law
If the distance between the bodies is many times greater than their size, then neither the shape nor the size of the charged bodies significantly affect the interactions between them. In this case, these bodies can be considered as point bodies.
The force of interaction of charged bodies depends on the properties of the medium between the charged bodies.
The force of interaction of two point motionless charged bodies in vacuum is directly proportional to the product of the charge modules and inversely proportional to the square of the distance between them. This force is called the Coulomb force.
|q 1 | and | q 2 | - modules of charges of bodies,
r- the distance between them,
k- coefficient of proportionality.
F- interaction force
The interaction forces of two motionless point charged bodies are directed along the straight line connecting these bodies.
Unit of electric charge
The unit of current is the ampere.
One pendant(1 Cl) - this is the charge passing in 1 s through the cross section of the conductor at a current strength of 1 A
g [Coulomb=Cl]
e=1.610 -19 C 
- electrical constant
CLOSE AND DISTANCE ACTION
The assumption that the interaction between bodies distant from each other is always carried out with the help of intermediate links (or medium) that transfer the interaction from point to point, is the essence of the theory of short-range action. Distribution with final speed.
Theory of direct action at a distance directly across the void. According to this theory, action is transmitted instantaneously over arbitrarily long distances.
Both theories are mutually opposed to each other. According to theories of action at a distance one body acts on another directly through the void and this action is transmitted instantly.
Short range theory states that any interaction is carried out with the help of intermediate agents and propagates with a finite speed.
The existence of a certain process in space between interacting bodies, which lasts a finite time, is the main thing that distinguishes the theory short-range action from the theory of action at a distance.
According to Faraday's idea electric charges do not act directly on each other. Each of them creates an electric field in the surrounding space. The field of one charge acts on another charge, and vice versa. As you move away from the charge, the field weakens.
Electromagnetic interactions must propagate in space at a finite speed.
The electric field exists in reality, its properties can be studied empirically, but we cannot say what this field consists of.
About the nature of the electric field, we can say that the field is material; it is noun. independently of us, from our knowledge of it;
The field has certain properties that do not allow it to be confused with anything else in the surrounding world;
The main property of an electric field is its action on electric charges with a certain force;
The electric field of stationary charges is called electrostatic. It doesn't change with time. An electrostatic field is created only by electric charges. It exists in the space surrounding these charges and is inextricably linked with it.
Electric field strength.
The ratio of the force acting on a charge placed at a given point of the field to this charge for each point of the field does not depend on the charge and can be considered as a characteristic of the field.
The field strength is equal to the ratio of the force with which the field acts on a point charge to this charge.
Field strength of a point charge.
.
Field strength modulus of a point charge q o on distance r from it is equal to:
.
If at a given point in space, various charged particles create electric fields, the strengths of which 
etc., then the resulting field strength at this point is:
POWER LINES OF THE ELECTRIC POL.
FIELD STRENGTH OF THE CHARGED BALL
An electric field whose intensity is the same at all points in space is called homogeneous.
The density of field lines is greater near charged bodies, where the field strength is also greater.
- field strength of a point charge.
Inside the conducting ball (r > R), the field strength is zero.
CONDUCTORS IN ELECTRIC FIELD.
Conductors contain charged particles that can move inside the conductor under the influence of an electric field. The charges of these particles are called free charges.
There is no electrostatic field inside the conductor. The entire static charge of a conductor is concentrated on its surface. Charges in a conductor can only be located on its surface.
Under normal conditions, microscopic bodies are electrically neutral because the positively and negatively charged particles that form atoms are connected to each other by electrical forces and form neutral systems. If the electrical neutrality of the body is violated, then such a body is called electrified body. To electrify a body, it is necessary that an excess or deficiency of electrons or ions of the same sign be created on it.
Methods of electrification of bodies, which represent the interaction of charged bodies, can be as follows:
- Electrification of bodies upon contact. In this case, with close contact, a small part of the electrons passes from one substance, in which the bond with the electron is relatively weak, to another substance.
- Electrization of bodies during friction. This increases the contact area of the bodies, which leads to increased electrification.
- Influence. Influence is based phenomenon of electrostatic induction, that is, the induction of an electric charge in a substance placed in a constant electric field.
- Electrification of bodies under the action of light. This is based on photoelectric effect, or photoelectric effect when, under the action of light, electrons can fly out of the conductor into the surrounding space, as a result of which the conductor is charged.
Numerous experiments show that when body electrification, then electric charges appear on the bodies, equal in magnitude and opposite in sign.
negative charge body is due to an excess of electrons on the body compared to protons, and positive charge due to a lack of electrons.
When the electrification of the body occurs, that is, when the negative charge is partially separated from the positive charge associated with it, law of conservation of electric charge. The law of conservation of charge is valid for a closed system, which does not enter from the outside and from which charged particles do not go out. The law of conservation of electric charge is formulated as follows:
In a closed system, the algebraic sum of the charges of all particles remains unchanged:
q 1 + q 2 + q 3 + ... + q n = const
where q 1 , q 2 etc. are the particle charges.
Interaction of electrically charged bodies
Interaction of bodies, having charges of the same or different signs, can be demonstrated in the following experiments. We electrify the ebonite stick by rubbing against the fur and touch it to a metal sleeve suspended on a silk thread. Charges of the same sign (negative charges) are distributed on the sleeve and ebonite stick. Approaching a negatively charged ebonite rod to a charged cartridge case, one can see that the cartridge case will be repelled from the stick (Fig. 1.2).
Rice. 1.2. Interaction of bodies with charges of the same sign.
If we now bring a glass rod rubbed on silk (positively charged) to the charged sleeve, then the sleeve will be attracted to it (Fig. 1.3).
Rice. 1.3. Interaction of bodies with charges of different signs.
It follows that bodies with charges of the same sign (like charged bodies) repel each other, and bodies with charges of a different sign (oppositely charged bodies) attract each other. Similar inputs are obtained if two sultans are brought closer, similarly charged (Fig. 1.4) and oppositely charged (Fig. 1.5).
Law of conservation of charge
Not all natural phenomena can be understood and explained on the basis of the concepts and laws of mechanics, the molecular-kinetic theory of the structure of matter, and thermodynamics. These sciences do not say anything about the nature of the forces that bind individual atoms and molecules, hold the atoms and molecules of matter in a solid state at a certain distance from each other. The laws of interaction of atoms and molecules can be understood and explained on the basis of the idea that electric charges exist in nature.
The simplest and most everyday phenomenon, in which the fact of the existence of electric charges in nature, is the electrification of bodies upon contact. The interaction of bodies detected during electrization is called electromagnetic interaction, and the physical quantity that determines electromagnetic interaction is called electric charge. The ability of electric charges to attract and repel indicates the presence of two different types of charges: positive and negative.
Electric charges can appear not only as a result of electrification when bodies come into contact, but also during other interactions, for example, under the influence of force (piezoelectric effect). But always in a closed system, which does not include charges, for any interactions of bodies, the algebraic (ie, taking into account the sign) sum of electric charges of all bodies remains constant. This experimentally established fact is called the law of conservation of electric charge.
Nowhere and never in nature do electric charges of the same sign arise and disappear. The appearance of a positive charge is always accompanied by the appearance of a negative charge equal in absolute value, but opposite in sign. Neither positive nor negative charges can disappear separately from each other if they are equal in absolute value.
The appearance and disappearance of electric charges on bodies in most cases is explained by the transitions of elementary charged particles - electrons - from one body to another. As you know, the composition of any atom includes a positively charged nucleus and negatively charged electrons. In a neutral atom, the total charge of the electrons is exactly equal to the charge of the atomic nucleus. A body consisting of neutral atoms and molecules has a total electric charge equal to zero.
If, as a result of any interaction, part of the electrons passes from one body to another, then one body receives a negative electric charge, and the second - a positive charge equal in absolute value. When two oppositely charged bodies come into contact, usually electric charges do not disappear without a trace, and an excess number of electrons passes from a negatively charged body to a body in which some of the atoms had an incomplete set of electrons on their shells.
A special case is the meeting of elementary charged antiparticles, for example, an electron and a positron. In this case, positive and negative electric charges really disappear, annihilate, but in full accordance with the law of conservation of electric charge, since the algebraic sum of the charges of an electron and a positron is equal to zero.
