Absolutely everyone knows such a concept as the law of conservation of energy. Energy does not arise from nothing and does not disappear into anywhere. It only passes from one form to another.
This is the fundamental law of the universe. It is thanks to this law that the Universe can exist stably and continuously.
The formulation of the law of conservation of charge
There is another similar law, which is also one of the fundamental ones. This is the law of conservation of electric charge.
In bodies that are at rest and electrically neutral, charges of opposite signs are equal in magnitude and mutually cancel each other out. When some bodies are electrified by others, charges are transferred from one body to another, but their total total charge remains the same.
In an isolated system of bodies, the total total charge is always equal to some constant value: q_1 + q_2 + ⋯ + q_n \u003d const, where q_1, q_2,…, q_n are the charges of bodies or particles included in the system.
What about the transformation of particles?
There is one point that can raise questions about particle transformation. Indeed, particles can give birth and disappear, while passing into other particles, radiation or energy.
Moreover, such processes can occur with both neutral and charge-carrying particles. What about the law of conservation of charge in this case?
It turned out that the birth and disappearance of particles can only occur in pairs. That is, particles pass into a different type of existence, for example, into radiation only by a pair, when both positive and negative particles disappear simultaneously.
In this case, a certain type of radiation and a certain energy appear. In the opposite case, when charged particles are born under the influence of some radiation and energy consumption, then they are also born only as a pair: positive and negative.
Accordingly, the total charge of the newly appeared pair of particles will be equal to zero and the law of conservation of charge is fulfilled.
Experimental confirmation of the law
The fulfillment of the law of conservation of electric charge has been confirmed experimentally many times. There is not a single fact that would say otherwise.
Therefore, scientists believe that the total electric charge of all bodies in the Universe remains unchanged and, most likely, is equal to zero. That is, the number of all positive charges is equal to the number of all negative charges.
The nature of the existence of the charge conservation law is still unclear. In particular, it is not clear why charged particles are born and annihilated only in pairs.
The law of conservation of charge states that during the interaction of a closed system with the surrounding space, the amount of charge that leaves the system through its surface is equal to the amount of charge that entered the system. In other words, the algebraic sum of all charges in the system is zero.
Formula 1 - Law of conservation of charge
As you know, there are two types of charges in nature. These are positive and negative. Also, the amount of charge is discrete, that is, it can only change in portions. An elementary charge is the charge of an electron. If one electron is added to an atom, then it becomes a negatively charged ion. And if you take it away then positive.
The main idea of \u200b\u200bthe law of conservation of charge is that the charge does not arise from nowhere and does not disappear into nowhere. When a charge of the same sign appears, a charge of the opposite sign of the same magnitude appears immediately.
To confirm this law, we will conduct an experiment. For it we need two electrometers. These are devices that show electrically charge. It consists of a rod on which an axle is fixed. There is an arrow on the axis. All this is placed in a cylindrical case, closed on both sides by glass.
There is a metal disc on the rod of the first electrometer. On which we will place another similar disk. It is necessary to lay an insulator between the discs. For example, cloth. The top disc has a dielectric handle. Grasping this handle, rub the discs together. Thus, electrifying them.
Figure 1 - Electrometers with disks fixed on them
After we remove the top disc, the electrometer will show the presence of a charge. The arrow will deviate from him. Next, we take the disc and touch it to the rod of the second electrometer. It also has an arrow deflecting, indicating the presence of a charge. Although the charge will be of the opposite sign. Further, if we connect the electrometer rods, the arrows will return to their original position. That is, the charges cancel each other out.
Figure 2 - compensation of disk charges
What happened in this experiment. When we rubbed the discs against each other, there was a charge separation in the metal of the discs. Initially, each disc was electrically neutral. One of them received an excess of electrons, that is, a negative charge. The other got a shortage of electrons, that is, he became, positively charged.
The charges in this case did not appear out of nowhere. They were already inside the conductive discs. Only they were compensated among themselves. We just separated them. By placing it on different disks. When we connected the electrometer rods, the charges were again compensated with each other. What the arrows testified to.
If we consider electrometers and disks as a single system. That despite all our manipulations, the total charge of this system was constant all the time. Initially, the discs were electrically neutral. After separation, volumetric positive and negative charges appeared. But they were the same in size. This means that the charge in the system remains the same. After connecting the rods, the system returned to its original state.
Electrostatics studies the properties and interactions of charges that are motionless in the frame of reference in which they are considered.
There are only two types of electric charges in nature - negative and positive. A positive charge can appear on a glass rod rubbed with leather, and a negative charge on amber rubbed with a woolen cloth.
It is known that all bodies are composed of atoms. In turn, an atom consists of a positively charged nucleus and electrons that revolve around it. Since electrons have a negative charge, and the nucleus is positive, the atom as a whole is electrically neutral. When exposed to it from outside, it can lose one or more electrons and turn into a positively charged ion. If an atom (or molecule) attaches an additional electron to itself, it will turn into a negative ion.
Thus, an 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 some body has a positive charge, it does not have enough electrons, and if it is negative, then it has an excess.
The electrical properties of any substance are due to its atomic structure. Atoms can even lose several electrons, in which case they are called multiply ionized. The nucleus of an atom consists of protons and neutrons. Each proton carries a charge that is equal to the charge of an electron, but opposite in sign. Neutrons are electrically neutral particles (they 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 a charge equal to the charge of an electron. It is also called the elementary charge, which is 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 amount of the electron charge.
If a positively charged body begins to recharge (charge with negative electricity), then its charge will not change instantly, but at first it will decrease to zero, and only then will it acquire a negative potential. Hence 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.
During electrification by friction, the negative and positive "elements" contained in the "uncharged body" are separated. As a result of the movement of negative elements of the body (electrons), both bodies are electrified, one of them being negative and the other positive. The amount of charges "flowing" from one element to another remains constant throughout the entire process.
Hence, we can conclude that charges not are created and do not disappear, but simply "flow" from one body to another or move inside it.This is the essence of the law of conservation of electric charges. Many materials are subject to electrification during friction - ebonite, glass and many others. In many industries (textiles, paper and others), the presence of static electricity is a serious engineering problem, since electrification of elements caused by friction of paper, fabric or other manufactured products against machine parts can cause fires and explosions.
The charge conservation law can be formulated in a shorter form - 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.
Electric charge is the ability of bodies to be a source of electromagnetic fields. This is the encyclopedic definition of an important electrical quantity. The main laws associated with it are the Coulomb and conservation of charge law. In this article we will consider the law of conservation of electric charge, we will try to define in simple words and provide all the necessary formulas.
The concept "" was first introduced in 1875 this year. The wording claims that the force that acts between two charged particles directed in a straight line is directly proportional to the charge and inversely proportional to the square of the distance between them.
This means that by moving the charges 2 times, the force of their interaction will decrease four times. And this is how it looks in vector form:
Applicability limit of the above:
- point charges;
- uniformly charged bodies;
- its action is valid at large and short distances.
Charles Coulomb's merits in the development of modern electrical engineering are great, but let's move on to the main topic of the article - the law of conservation of charge. He claims that the sum of all charged particles in a closed system is unchanged. In simple words, charges cannot arise or disappear just like that. At the same time, it does not change in time and it can be measured (or divided, quantized) in parts that are multiples of an elementary electric charge, that is, an electron.
But remember that in an isolated system, new charged particles appear only under the influence of certain forces or as a result of any processes. So ions arise as a result of the ionization of gases, for example.
If you are concerned about the question, who and when discovered the law of conservation of charge? It was confirmed in 1843 by the great scientist - Michael Faraday. In experiments confirming the conservation law, the amount of charges is measured by electrometers, its appearance is shown in the figure below:
But let's confirm our words with practice. Take two electrometers, put a metal disk on the rod of one, cover it with a cloth. Now we need another metal disc on the dielectric handle. There are three of it on a disk lying on an electrometer, and they become electrified. When the disk with the dielectric handle is removed, the electrometer will show how charged it has become, with the disk with the dielectric handle we touch the second electrometer. Its arrow will also deviate. If we now close two electrometers with a rod on the dielectric handles, their arrows will return to their original position. This suggests that the total or resultant electric charge is zero, and its value in the system remains the same.
From here follows a formula describing the law of conservation of electric charge:
The following formula says that the change in the electric charge in the volume is equivalent to the total current through the surface. This is also called the "equation of continuity".
And if we go to a very small volume, we get the law of conservation of charge in differential form.
It is also important to tell how charge and mass number are related. When talking about the structure of substances, words such as molecules, atoms, protons and the like are often heard. So the mass number is the total number of protons and neutrons, and the number of protons and electrons in the nucleus is called the charge number. In other words, the charge number is called the charge of the nucleus, and it always depends on its composition. Well, the mass of an element depends on the number of its particles.
Thus, we briefly examined the issues related to the law of conservation of electric charge. It is one of the fundamental laws of physics along with the laws of conservation of momentum and energy. Its action is flawless and over time and the development of technology it is not possible to refute its validity. We hope that after reading our explanation, all the key points of this law have become clear to you!
Materials
Electrodynamics- the science of the properties of the electromagnetic field.
Electromagnetic field- is determined by the movement and interaction of charged particles.
Manifestation of electric / magnetic fieldis the action of electric / magnetic forces:
1) frictional forces and elastic forces in the macrocosm;
2) the action of electric / magnetic forces in the microcosm (the structure of the atom, the cohesion of atoms into molecules, the transformation of elementary particles)
Discovery of the electric / magnetic field - J. Maxwell.
ELECTROSTATICS
Section of electrodynamics, studies electrically charged bodies at rest.
Elementary particles may have email. charge, then they are called charged;
- interact with each other with forces that depend on the distance between particles, but many times exceed the forces of mutual gravity (this interaction is called electromagnetic).
Electric charge- a physical quantity that determines the intensity of electromagnetic interactions.
There are 2 signs of electric charges: positive and negative.
Particles with charges of the same name are repelled, with opposite charges, they are attracted.
The proton has a positive charge, the electron is negative, and the neutron is electrically neutral.
Elementary charge- the minimum charge, which cannot be divided.
How to explain the presence of electromagnetic forces in nature? - all bodies contain charged particles.
In the normal state, bodies are electrically neutral (since the atom is neutral), and electromagnetic forces are not manifested.
Body chargedif it has an excess of charges of any sign:
negatively charged - if there is an excess of electrons;
positively charged - if there is a lack of electrons.
Electrifying bodies - this is one of the ways to obtain charged bodies, for example, by contact).
In this case, both bodies are charged, and the charges are opposite in sign, but equal in magnitude.
In a closed system, the algebraic sum of the charges of all particles remains unchanged.
(... but not the number of charged particles, since there are transformations of elementary particles).
Closed system- a system of particles, which does not enter from the outside and do not leave charged particles.
The basic law of electrostatics.
The force of interaction of two point immobile charged bodies in a vacuum is directly proportional to the product of the charge modules and inversely proportional to the square of the distance between them.
When bodies are considered point? - if the distance between them is many times greater than the size of the bodies.
If two bodies have electric charges, then they interact according to the Coulomb's law.
Unit of electrical charge:1 C is a charge passing through the cross-section of the conductor in 1 second at a current of 1 A
1 Cl - very large charge
Elementary charge:
It is customary to write the coefficient of proportionality in the Coulomb's law in vacuum in the form
where is the electric constant
Coulomb's law for the magnitude of the interaction force of charges in an arbitrary medium (in SI):
The dielectric constant of a medium characterizes the electrical properties of the medium. In a vacuum
Thus, the Coulomb force depends on the properties of the medium between charged bodies.
Electrostatics and DC Laws - Classy Physics