As a result of long observations, scientists have found that oppositely charged bodies attract, and similarly charged bodies, on the contrary, repel. This means that interaction forces arise between bodies. The French physicist C. Coulomb experimentally studied the patterns of interaction between metal balls and found that the force of interaction between two point electric charges will be directly proportional to the product of these charges and inversely proportional to the square of the distance between them:

Where k is a coefficient of proportionality, depending on the choice of units of measurement of physical quantities that are included in the formula, as well as on the environment in which the electric charges q 1 and q 2 are located. r is the distance between them.

From here we can conclude that Coulomb’s law will only be valid for point charges, that is, for such bodies whose sizes can be completely neglected in comparison with the distances between them.

In vector form, Coulomb's law will look like:

Where q 1 and q 2 are charges, and r is the radius vector connecting them; r = |r|.

The forces that act on the charges are called central. They are directed in a straight line connecting these charges, and the force acting from charge q 2 on charge q 1 is equal to the force acting from charge q 1 on charge q 2 and is opposite in sign.

To measure electrical quantities, two number systems can be used - the SI (basic) system and sometimes the CGS system can be used.

In the SI system, one of the main electrical quantities is the unit of current - ampere (A), then the unit of electric charge will be its derivative (expressed in terms of the unit of current). The SI unit of charge is the coulomb. 1 coulomb (C) is the amount of “electricity” passing through the cross-section of a conductor in 1 s at a current of 1 A, that is, 1 C = 1 A s.

The coefficient k in formula 1a) in the SI is taken equal to:

And Coulomb’s law can be written in the so-called “rationalized” form:

Many equations describing magnetic and electrical phenomena contain a factor of 4π. However, if this factor is introduced into the denominator of Coulomb’s law, then it will disappear from most formulas of magnetism and electricity, which are very often used in practical calculations. This form of writing an equation is called rationalized.

The value ε 0 in this formula is the electrical constant.

The basic units of the GHS system are the GHS mechanical units (gram, second, centimeter). New basic units in addition to the above three are not introduced in the GHS system. The coefficient k in formula (1) is assumed to be equal to unity and dimensionless. Accordingly, Coulomb's law in a non-rationalized form will look like:

In the CGS system, force is measured in dynes: 1 dyne = 1 g cm/s 2, and distance in centimeters. Let's assume that q = q 1 = q 2 , then from formula (4) we get:

If r = 1 cm, and F = 1 dyne, then from this formula it follows that in the CGS system a unit of charge is taken to be a point charge, which (in a vacuum) acts on an equal charge, distant from it at a distance of 1 cm, with a force of 1 din. Such a unit of charge is called the absolute electrostatic unit of quantity of electricity (charge) and is denoted by CGS q. Its dimensions:

To calculate the value of ε 0, we compare the expressions for Coulomb’s law written in the SI and GHS systems. Two point charges of 1 C each, which are located at a distance of 1 m from each other, will interact with a force (according to formula 3):

In the GHS this force will be equal to:

The strength of interaction between two charged particles depends on the environment in which they are located. To characterize the electrical properties of various media, the concept of relative dielectric penetration ε was introduced.

The value of ε is a different value for different substances - for ferroelectrics its value lies in the range of 200 - 100,000, for crystalline substances from 4 to 3000, for glass from 3 to 20, for polar liquids from 3 to 81, for non-polar liquids from 1, 8 to 2.3; for gases from 1.0002 to 1.006.

The dielectric constant (relative) also depends on the ambient temperature.

If we take into account the dielectric constant of the medium in which the charges are placed, in SI Coulomb’s law takes the form:

Dielectric constant ε is a dimensionless quantity and it does not depend on the choice of units of measurement and for vacuum is considered equal to ε = 1. Then for vacuum Coulomb’s law takes the form:

Dividing expression (6) by (5) we get:

Accordingly, the relative dielectric constant ε shows how many times the interaction force between point charges in some medium, which are located at a distance r relative to each other less than in vacuum, at the same distance.

For the division of electricity and magnetism, the GHS system is sometimes called the Gauss system. Before the advent of the SGS system, the SGSE (SGS electrical) systems operated for measuring electrical quantities and the SGSM (SGS magnetic) systems for measuring magnetic quantities. The first equal unit was taken to be the electrical constant ε 0, and the second equal to the magnetic constant μ 0.

In the SGS system, the formulas of electrostatics coincide with the corresponding formulas of the SGSE, and the formulas of magnetism, provided that they contain only magnetic quantities, coincide with the corresponding formulas in the SGSM.

But if the equation simultaneously contains both magnetic and electrical quantities, then this equation written in the Gaussian system will differ from the same equation, but written in the SGSM or SGSE system by a factor of 1/s or 1/s 2 . The quantity c is equal to the speed of light (c = 3·10 10 cm/s) is called the electrodynamic constant.

Coulomb's law in the GHS system will have the form:

Example

Two absolutely identical drops of oil are missing one electron. The force of Newtonian attraction is balanced by the force of Coulomb repulsion. It is necessary to determine the radii of droplets if the distances between them significantly exceed their linear dimensions.

Solution

Since the distance r between the drops is significantly greater than their linear dimensions, the drops can be taken as point charges, and then the Coulomb repulsion force will be equal to:

Where e is the positive charge of the oil drop, equal to the charge of the electron.

The force of Newtonian attraction can be expressed by the formula:

Where m is the mass of the drop, and γ is the gravitational constant. According to the conditions of the problem, F k = F n, therefore:

The mass of a drop is expressed through the product of density ρ and volume V, that is, m = ρV, and the volume of a drop of radius R is equal to V = (4/3)πR 3, from which we obtain:

In this formula, the constants π, ε 0, γ are known; ε = 1; the electron charge e = 1.6·10 -19 C and the oil density ρ = 780 kg/m 3 (reference data) are also known. Substituting the numerical values ​​into the formula we get the result: R = 0.363·10 -7 m.

Just as in Newtonian mechanics gravitational interaction always takes place between bodies with masses, similarly in electrodynamics electrical interaction is characteristic of bodies with electric charges. Electric charge is indicated by the symbol “q” or “Q”.

One can even say that the concept of electric charge q in electrodynamics is somewhat similar to the concept of gravitational mass m in mechanics. But unlike gravitational mass, electric charge characterizes the property of bodies and particles to enter into force electromagnetic interactions, and these interactions, as you understand, are not gravitational.

Electric charges

Human experience in studying electrical phenomena contains many experimental results, and all these facts allowed physicists to come to the following unambiguous conclusions regarding electric charges:

1. Electric charges are of two types - they can be conditionally divided into positive and negative.

2. Electrical charges can be transferred from one charged object to another: for example, by contacting bodies with each other - the charge between them can be divided. Moreover, the electric charge is not at all an obligatory component of the body: under different conditions, the same object may have a charge of different magnitude and sign, or the charge may be absent. Thus, the charge is not something inherent in the carrier, and at the same time, the charge cannot exist without the charge carrier.

3. While gravitating bodies are always attracted to each other, electric charges can both attract and repel each other. Like charges attract each other, like charges repel each other.

The law of conservation of electric charge is a fundamental law of nature, it sounds like this: “the algebraic sum of the charges of all bodies inside an isolated system remains constant.” This means that inside a closed system it is impossible for charges of only one sign to appear or disappear.

Today, the scientific point of view is that initially charge carriers are elementary particles. The elementary particles neutrons (electrically neutral), protons (positively charged) and electrons (negatively charged) form atoms.

Protons and neutrons make up the nuclei of atoms, and electrons form the shells of atoms. The moduli of the charges of the electron and proton are equal in magnitude to the elementary charge e, but the charges of these particles are opposite in sign.

As for the direct interaction of electric charges with each other, in 1785 the French physicist Charles Coulomb experimentally established and described this basic law of electrostatics, a fundamental law of nature that does not follow from any other laws. In his work, the scientist studied the interaction of stationary point charged bodies and measured the forces of their mutual repulsion and attraction.

Coulomb experimentally established the following: “The forces of interaction between stationary charges are directly proportional to the product of the modules and inversely proportional to the square of the distance between them.”

This is the formulation of Coulomb's Law. And although point charges do not exist in nature, only in relation to point charges can we talk about the distance between them, within the framework of this formulation of Coulomb’s Law.

In fact, if the distances between the bodies greatly exceed their sizes, then neither the size nor the shape of the charged bodies will particularly affect their interaction, which means that the bodies for this task can rightly be considered point-like.

Let's consider this example. Let's hang a couple of charged balls on strings. Since they are somehow charged, they will either repel each other or attract each other. Since the forces are directed along the straight line connecting these bodies, these forces are central.

To denote the forces acting from each of the charges on the other, we write: F12 is the force of action of the second charge on the first, F21 is the force of action of the first charge on the second, r12 is the radius vector from the second point charge to the first. If the charges have the same sign, then the force F12 will be codirectional to the radius vector, but if the charges have different signs, F12 will be directed opposite to the radius vector.

Using the law of interaction of point charges (Coulomb's Law), you can now find the interaction force for any point charges or point charged bodies. If the bodies are not point-like, then they are mentally broken down into chalk elements, each of which could be mistaken for a point charge.

After finding the forces acting between all small elements, these forces are added geometrically and the resulting force is found. Elementary particles also interact with each other according to Coulomb's Law, and to this day no violations of this fundamental law of electrostatics have been observed.

In modern electrical engineering there is no area where Coulomb’s Law does not work in one form or another. Starting with electric current, ending with a simply charged capacitor. Especially those areas that relate to electrostatics - they are 100% related to Coulomb's Law. Let's look at just a few examples.

The simplest case is the introduction of a dielectric. The force of interaction of charges in a vacuum is always greater than the force of interaction of the same charges under conditions when some kind of dielectric is located between them.

The dielectric constant of a medium is precisely the quantity that allows us to quantify the values ​​of forces, regardless of the distance between the charges and their magnitudes. It is enough to divide the force of interaction of charges in a vacuum by the dielectric constant of the introduced dielectric - we obtain the force of interaction in the presence of the dielectric.

Complex research equipment - charged particle accelerator. The operation of charged particle accelerators is based on the phenomenon of interaction between the electric field and charged particles. The electric field does work in the accelerator, increasing the energy of the particle.

If we consider here the accelerated particle as a point charge, and the action of the accelerating electric field of the accelerator as the total force from other point charges, then in this case Coulomb’s Law is fully observed. The magnetic field only directs the particle by the Lorentz force, but does not change its energy, it only sets the trajectory for the movement of particles in the accelerator.

Protective electrical structures. Important electrical installations are always equipped with such a simple thing at first glance as a lightning rod. And a lightning rod cannot do its work without observing Coulomb’s Law. During a thunderstorm, large induced charges appear on Earth - according to Coulomb's Law, they are attracted in the direction of the thundercloud. This results in a strong electric field on the Earth's surface.

The intensity of this field is especially high near sharp conductors, and therefore a corona discharge is ignited at the pointed end of the lightning rod - a charge from the Earth tends, in obedience to Coulomb's Law, to be attracted to the opposite charge of a thundercloud.

The air near the lightning rod is highly ionized as a result of a corona discharge. As a result, the electric field strength near the tip decreases (as well as inside any conductor), induced charges cannot accumulate on the building and the likelihood of lightning occurring is reduced. If lightning happens to strike the lightning rod, the charge will simply go into the Earth and will not damage the installation.

Topic 1.1 ELECTRIC CHARGES.

Section 1 BASICS OF ELECTRODYNAMICS

1. Electrification of bodies. The concept of charge magnitude.

Law of conservation of charge.

2. Interaction forces between charges.

Coulomb's law.

3. Dielectric constant of the medium.

4. International system of units in electricity.

1. Electrification of bodies. The concept of charge magnitude.

Law of conservation of charge.

If two surfaces are brought into close contact, then possible electron transfer from one surface to another, and electrical charges appear on these surfaces.

This phenomenon is called ELECTRIZATION. During friction, the area of ​​close contact of surfaces increases, and the amount of charge on the surface also increases - this phenomenon is called ELECTRICATION BY FRICTION.

During the process of electrification, a redistribution of charges occurs, as a result of which both surfaces are charged with charges of equal magnitude and opposite in sign.

Because all electrons have the same charges (negative) e = 1.6 10 C, then in order to determine the amount of charge on the surface (q), it is necessary to know how many electrons are in excess or deficiency on the surface (N) and the charge of one electron.

During the process of electrification, new charges do not appear or disappear, but only occur redistribution between bodies or parts of a body, therefore the total charge of a closed system of bodies remains constant, this is the meaning of the LAW OF CONSERVATION OF CHARGE.

2. Interaction forces between charges.

Coulomb's law.

Electric charges interact with each other while located at a distance, while like charges repel, and unlike charges attract.

First time I found out experienced How does the force of interaction between charges depend? The French scientist Coulomb derived a law called Coulomb's law. Fundamental law i.e. based on experience. When deducing this law, Coulomb used torsion balances.

3) k – coefficient expressing dependence on the environment.

Formula of Coulomb's law.

The force of interaction between two stationary point charges is directly proportional to the product of the magnitudes of these charges and inversely proportional to the square of the distances between them, and depends on the environment in which these charges are located, and is directed along the straight line connecting the centers of these charges.

3. Dielectric constant of the medium.

E is the dielectric constant of the medium, depending on the surrounding medium charges.

E = 8.85*10 - physical constant, dielectric constant of vacuum.

E – relative dielectric constant of the medium, shows how many times the force of interaction between point charges in a vacuum is greater than in a given medium. In a vacuum, the interaction between charges is strongest.

4. International system of units in electricity.

The basic unit for electricity in the SI system is current in 1A, all other units of measurement are derived from 1Ampere.

1C is the amount of electric charge transferred by charged particles through the cross-section of a conductor at a current of 1A in 1s.

q=N;

Topic 1.2 ELECTRIC FIELD

1. Electric field – as a special type of matter.

6. Relationship between potential difference and electric field strength.

1. The electric field is like a special type of matter.

In nature, an electromagnetic field exists as a type of matter. In different cases, the electromagnetic field manifests itself in different ways, for example, near stationary charges only an electric field manifests itself, which is called electrostatic. Both electric and magnetic fields can be detected near moving charges, which together represent ELECTROMAGNETIC FIELDS.

Let's consider the properties of electrostatic fields:

1) The electrostatic field is created by stationary charges; such fields can be detected

using test charges (small positive charge), because only on them the electric field has a force effect, which obeys Coulomb’s law.

2. Electric field strength.

The electric field as a type of matter has energy, mass, propagates in space with a finite speed and has no theoretical boundaries.

In practice, it is considered that there is no field if it does not have a noticeable effect on the test charges.

Since the field can be detected using force on test charges, the main characteristic of the electric field is tension.

If test charges of different magnitudes are introduced into the same point of the electric field, then there is a direct proportional relationship between the acting force and the value of the test charge.

The coefficient of proportionality between the acting force and the magnitude of the charge is the tension E.

E = formula for calculating the electric field strength, if q = 1 C, then | E | = | F |

Tension is a force characteristic of electric field points, because it is numerically equal to the force acting on a charge of 1 C at a given point in the electric field.

Tension is a vector quantity, the vector of tension in direction coincides with the vector of the force acting on the positive charge at a given point in the electric field.

3. Electric field strength lines. Uniform electric field.

In order to clearly depict the electric field, i.e. graphically, use electric field strength lines. These are lines, otherwise called lines of force, the tangents to which in direction coincide with the intensity vectors at the points of the electric field through which these lines pass,

Tension lines have the following properties:

1) Start in position. charges end on negative, or begin on positive. charges and go to infinity, or come from infinity and end on positive charges..

2) These lines are continuous and do not intersect anywhere.

3) The density of lines (the number of lines per unit surface area) and the electric field strength are in direct and proportional dependence.

In a uniform electric field, the intensity at all points of the field is the same; graphically, such fields are represented by parallel lines at an equal distance from each other. Such a field can be obtained between two parallel flat charged plates at a small distance from each other.

4. Work on moving a charge in an electric field.

Let us place an electric charge in a uniform electric field. Forces will act on the charge from the field. If a charge is moved, work can be done.

Perfect work in areas:

A = q E d - formula for calculating the work of moving a charge in an electric field.

Conclusion: The work of moving a charge in an electric field does not depend on the shape of the trajectory, but it depends on the magnitude of the moved charge (q), field strength (E), as well as on the choice of the starting and ending points of movement (d).

If a charge in an electric field is moved along a closed circuit, then the work done will be equal to 0. Such fields are called potential fields. Bodies in such fields have potential energy, i.e. an electric charge at any point in the electric field has energy and the work done in the electric field is equal to the difference in the potential energies of the charge at the initial and final points of movement.

5. Potential. Potential difference. Voltage.

If charges of different sizes are placed at a given point in the electric field, then the potential energy of the charge and its magnitude are directly proportional.

-(phi) potential of an electric field point

let's accept

Potential is an energy characteristic of electric field points, because it is numerically equal to the potential energy of a charge of 1 C at a given point in the electric field.

At equal distances from a point charge, the potentials of the field points are the same. These points form a surface of equal potential, and such surfaces are called equipotential surfaces. On the plane these are circles, in space they are spheres.

Voltage

Formulas for calculating the work of moving a charge in an electric field.

1V is the voltage between points of the electric field when moving a charge of 1 C and doing 1 J of work.

- a formula establishing the relationship between the electric field strength, voltage and potential difference.

The tension is numerically equal to the voltage or potential difference between two points of the field taken along one field line at a distance of 1 m. The (-) sign means that the voltage vector is always directed towards the field points with decreasing potential.

It is known that every charged body has an electric field. It can also be argued that if there is an electric field, then there is a charged body to which this field belongs. So, if there are two charged bodies with electric charges nearby, then we can say that each of them is in the electric field of the neighboring body. And in this case, the force will act on the first body

F 1 =q 1E2,

Where q 1— charge of the first body; E 2— field strength of the second body. The second body, accordingly, will be acted upon by a force

F 2 =q 2E 1,

Where q 2— charge of the first body; E 1— field strength of the second body.

An electrically charged body interacts with the electric field of another charged body.

If these bodies are small (point-like), then

E 1 =k. q 1 / r 2 ,

E 2 =k.q 2 /r2,

The forces acting on each of the interacting charged bodies can be calculated by knowing only their charges and the distance between them.

Let's substitute the tension values ​​and get

F 1 = k. q 1 q 2 / r 2 And F 2 = k. q 2 q 1 / r 2 .

The value of each force is expressed only through the value of the charges of each body and the distance between them. Thus, it is possible to determine the forces acting on each body using only knowledge about the electric charges of bodies and the distance between them. On this basis, one of the fundamental laws of electrodynamics can be formulated - Coulomb's law.

Coulomb's law . The force acting on a stationary point body with an electric charge in the field of another stationary point body with an electric charge is proportional to the product of the values ​​of their charges and inversely proportional to the square of the distance between them.

In general terms, the meaning of the force referred to in the formulation Coulomb's law, can be written like this:

F = k. q 1 q 2 / r 2 ,

The formula for calculating the force of interaction contains the values ​​of the charges of both bodies. Therefore, we can conclude that both forces are equal in magnitude. However, in direction they are opposite. If the charges of the bodies are the same, the bodies repel (Fig. 4.48). If the charges of the bodies are opposite, then the bodies attract (Fig. 4.49). Finally we can write:

F̅ 1 = -F̅ 2.

The written equality confirms the validity of Newton's third law of dynamics for electrical interactions. Therefore, in one of the common formulations Coulomb's law it is said that

the force of interaction between two charged point bodies is proportional to the product of the values ​​of their charges and inversely proportional to the square of the distance between them.

If charged bodies are in a dielectric, then the force of interaction will depend on the dielectric constant of this dielectric

F=k.q 1q 2 /ε r 2.

For the convenience of calculations based on Coulomb’s law, the value of the coefficient k written differently:

k = 1/4πε 0 .

Magnitude ε 0 called electric constant. Its value is calculated in accordance with the definition:

9 . 10 9 N.m 2 /Cl 2 = 1 / 4π ε 0 ,

ε 0 = (1 / 4π) . 9 . 10 9 N.m 2 / Cl 2 = 8.85. 10 -12 C 2 / N.m 2. Material from the site

Thus, Coulomb's law in the general case can be expressed by the formula

F= (1 / 4π ε 0 ) . q 1 q 2 / ε r 2 .

Coulomb's law is one of the fundamental laws of nature. All electrodynamics is based on it, and not a single case has been noted in which Coulomb's law. There is only one limitation that concerns the action Coulomb's law at various distances. It is believed that Coulomb's law valid at distances greater than 10 -16 m and less than several kilometers.

When solving problems, it is necessary to take into account that Coulomb’s law concerns the interaction forces of point-like stationary charged bodies. This reduces all problems to problems about the interaction of stationary charged bodies, in which two static provisions are used:

1. the resultant of all forces acting on the body is equal to zero;
2. the sum of the moments of forces is zero.

In the vast majority of application tasks Coulomb's law it is enough to take into account only the first position.

On this page there is material on the following topics:

• Write down the formula for Coulomb's law

• Coulomb's law abstract

• Physics report on the topic of Coulomb's law

• Publications based on materials by D. Giancoli. "Physics in two volumes" 1984 Volume 2.

  There is a force between electric charges. How does it depend on the magnitude of the charges and other factors?
  This question was explored in the 1780s by the French physicist Charles Coulomb (1736-1806). He used torsion balances very similar to those used by Cavendish to determine the gravitational constant.
  If a charge is applied to a ball at the end of a rod suspended on a thread, the rod is slightly deflected, the thread twists, and the angle of rotation of the thread will be proportional to the force acting between the charges (torsion balance). Using this device, Coulomb determined the dependence of force on the size of charges and the distance between them.

  At that time, there were no instruments to accurately determine the amount of charge, but Coulomb was able to prepare small balls with a known charge ratio. If a charged conducting ball, he reasoned, is brought into contact with exactly the same uncharged ball, then the charge present on the first ball, due to symmetry, will be distributed equally between the two balls.
  This gave him the ability to receive charges of 1/2, 1/4, etc. from the original one.
  Despite some difficulties associated with the induction of charges, Coulomb was able to prove that the force with which one charged body acts on another small charged body is directly proportional to the electric charge of each of them.
  In other words, if the charge of any of these bodies is doubled, the force will also be doubled; if the charges of both bodies are doubled at the same time, the force will become four times greater. This is true provided that the distance between the bodies remains constant.
  By changing the distance between bodies, Coulomb discovered that the force acting between them is inversely proportional to the square of the distance: if the distance, say, doubles, the force becomes four times less.

  So, Coulomb concluded, the force with which one small charged body (ideally a point charge, i.e. a body like a material point that has no spatial dimensions) acts on another charged body is proportional to the product of their charges Q 1 and Q 2 and is inversely proportional to the square of the distance between them:

  

  Here k- proportionality coefficient.
  This relationship is known as Coulomb's law; its validity has been confirmed by careful experiments, much more accurate than Coulomb's original, difficult to reproduce experiments. The exponent 2 is currently established with an accuracy of 10 -16, i.e. it is equal to 2 ± 2×10 -16.

  Since we are now dealing with a new quantity - electric charge, we can select a unit of measurement so that the constant k in the formula is equal to one. Indeed, such a system of units was widely used in physics until recently.
  

  We are talking about the CGS system (centimeter-gram-second), which uses the electrostatic charge unit SGSE. By definition, two small bodies, each with a charge of 1 SGSE, located at a distance of 1 cm from each other, interact with a force of 1 dyne.

  Now, however, charge is most often expressed in the SI system, where its unit is the coulomb (C).
  We will give the exact definition of a coulomb in terms of electric current and magnetic field later.
  In the SI system the constant k has the magnitude k= 8.988×10 9 Nm 2 / Cl 2.

  The charges arising during electrification by friction of ordinary objects (combs, plastic rulers, etc.) are in the order of magnitude a microcoulomb or less (1 µC = 10 -6 C).
  The electron charge (negative) is approximately 1.602×10 -19 C. This is the smallest known charge; it has a fundamental meaning and is represented by the symbol e, it is often called the elementary charge.
  e= (1.6021892 ± 0.0000046)×10 -19 C, or e≈ 1.602×10 -19 Cl.

  Since a body cannot gain or lose a fraction of an electron, the total charge of the body must be an integer multiple of the elementary charge. They say that the charge is quantized (that is, it can take only discrete values). However, since the electron charge e is very small, we usually do not notice the discreteness of macroscopic charges (a charge of 1 μC corresponds to approximately 10 13 electrons) and consider the charge to be continuous.

  The Coulomb formula characterizes the force with which one charge acts on another. This force is directed along the line connecting the charges. If the signs of the charges are the same, then the forces acting on the charges are directed in opposite directions. If the signs of the charges are different, then the forces acting on the charges are directed towards each other.
  Note that, in accordance with Newton's third law, the force with which one charge acts on another is equal in magnitude and opposite in direction to the force with which the second charge acts on the first.
  Coulomb's law can be written in vector form, similar to Newton's law of universal gravitation:

  

  Where F 12 - vector of force acting on the charge Q 1 charge side Q 2,
  - distance between charges,
  - unit vector directed from Q 2 k Q 1.
  It should be borne in mind that the formula is applicable only to bodies the distance between which is significantly greater than their own dimensions. Ideally, these are point charges. For bodies of finite size, it is not always clear how to calculate the distance r between them, especially since the charge distribution may be non-uniform. If both bodies are spheres with a uniform charge distribution, then r means the distance between the centers of the spheres. It is also important to understand that the formula determines the force acting on a given charge from a single charge. If the system includes several (or many) charged bodies, then the resulting force acting on a given charge will be the resultant (vector sum) of the forces acting on the part of the remaining charges. The constant k in the Coulomb Law formula is usually expressed in terms of another constant, ε 0 , the so-called electrical constant, which is related to k ratio k = 1/(4πε 0). Taking this into account, Coulomb's law can be rewritten as follows:

  

  where with the highest accuracy today

  or rounded

  Writing most other equations of electromagnetic theory is simplified by using ε 0 , because 4π the final result is often shortened. Therefore, we will generally use Coulomb's Law, assuming that:

  

  Coulomb's law describes the force acting between two charges at rest. When charges move, additional forces are created between them, which we will discuss in subsequent chapters. Here only charges at rest are considered; This section of the study of electricity is called electrostatics.

  To be continued. Briefly about the following publication:

  Electric field is one of two components of the electromagnetic field, which is a vector field that exists around bodies or particles with an electric charge, or that arises when the magnetic field changes.

  Comments and suggestions are accepted and welcome!

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