Mathematical expression of Boyle Marriott's law. Boyle-Mariotte law

The action of a charged body on surrounding bodies manifests itself in the form of forces of attraction and repulsion, tending to rotate and move these bodies in relation to the charged body. We observed the manifestation of these forces in the experiments described in the previous paragraphs. They can also be observed with the help of an instructive experiment, which we will now describe.

Let's pour some liquid dielectric (for example, oil) into a small glass cuvette (Fig. 25), to which powder with elongated grains is mixed. Let us place, for example, two metal plates in a cuvette and connect them to an electrical machine that allows us to continuously separate positive and negative charges. In order to conveniently monitor the behavior of grains suspended in oil, we project an image of the entire picture onto the screen or simply cast the shadow of the cuvette on the ceiling (Fig. 25). When charging the plates, you can see that individual grains, initially located completely randomly, begin to move and rotate and are eventually established in the form of chains stretching from one electrode to another. In Fig. Figure 26 shows an image of the arrangement of grains between two parallel metal plates, and in Fig. 27- between two metal balls.

Rice. 25. Diagram of the experimental setup for obtaining electric field patterns: 1 – cuvette containing castor oil with quinine crystals, 2 – conductors connected to an electrical machine and creating an electric field, 3 – light source, 4 – screen onto which the shadow of the crystals is projected

Rice. 26. Arrangement of grains between two parallel plates charged differently

Rice. 27. Arrangement of grains between two metal balls charged differently

In this experience, each grain is like a small arrow. The small size of the grains makes it possible to place them simultaneously at many points in the medium and thereby discover that the action of a charged body manifests itself at all points of space surrounding the charge. Thus, one can judge the existence of an electric charge in some place by the actions it performs at various points in the surrounding space.

Depending on the charge and shape of a charged body, its action at different points in space will be different. Therefore for full characteristics charge, you need to know what effect it produces at all possible points in the surrounding space, or, as they say, you need to know the electric field that arises around the charge. Thus, by the concept of “electric field” we designate the space in which the actions of an electric charge manifest themselves.

If there is not one, but several charges located in different places, then at any point in the surrounding space a joint action of these charges, the electric field created by all these charges.

Note that at the beginning of the study of electricity, there is often a desire to “explain” the electric field, that is, to reduce it to some other, already studied phenomena, just as thermal phenomena we reduce it to the random movement of atoms and molecules. However, numerous attempts of this kind in the field of electricity invariably ended in failure. Therefore, we should assume that the electric field is an independent physical reality, which is not reducible to either thermal or mechanical phenomena. Electrical phenomena represent a new class of natural phenomena that we become familiar with through experience, and our further task should be to study the properties of the electric field and its laws.

The action of a charged body on surrounding bodies manifests itself in the form of forces of attraction and repulsion, tending to rotate and move these bodies in relation to the charged body. We observed the manifestation of these forces in the experiments described in the previous paragraphs. They can also be observed with the help of an instructive experiment, which we will now describe.

Let's pour some liquid dielectric (for example, oil) into a small glass cuvette (Fig. 25), to which powder with elongated grains is mixed. Let's place, for example, two metal plates in a cuvette and connect them to an electrical machine that allows the continuous separation of positive and negative charges. In order to conveniently monitor the behavior of grains suspended in oil, we project an image of the entire picture onto the screen or simply cast the shadow of the cuvette on the ceiling (Fig. 25). When charging the plates, you can see that individual grains, initially located completely randomly, begin to move and rotate and are eventually established in the form of chains stretching from one electrode to another. In Fig. Figure 26 shows an image of the arrangement of grains between two parallel metal plates, and in Fig. 27- between two metal balls.

Rice. 25. Scheme experimental setup to obtain pictures of the electric field: 1 – a cuvette containing castor oil with quinine crystals, 2 – conductors connected to an electrical machine and creating an electric field, 3 – a light source, 4 – a screen on which the shadow of the crystals is projected

Rice. 26. Arrangement of grains between two parallel plates charged differently

Rice. 27. Arrangement of grains between two metal balls charged differently

In this experience, each grain is like a small arrow. The small size of the grains makes it possible to place them simultaneously at many points in the medium and thereby discover that the action of a charged body manifests itself at all points of space surrounding the charge. Thus, one can judge the existence of an electric charge in some place by the actions it performs at various points in the surrounding space.

Depending on the charge and shape of a charged body, its action at different points in space will be different. Therefore, to fully characterize a charge, you need to know what effect it produces at all possible points in the surrounding space, or, as they say, you need to know the electric field that arises around the charge. Thus, by the concept of “electric field” we designate the space in which the actions of an electric charge manifest themselves.

If there is not one, but several charges located in different places, then at any point in the surrounding space the combined action of these charges, the electric field created by all these charges, will appear.

Note that at the beginning of the study of electricity, there is often a desire to “explain” the electric field, that is, to reduce it to some other, already studied phenomena, just as we reduce thermal phenomena to the random movement of atoms and molecules. However, numerous attempts of this kind in the field of electricity invariably ended in failure. Therefore, it should be considered that the electric field is an independent physical reality that cannot be reduced to either thermal or mechanical phenomena. Electrical phenomena are new class natural phenomena that we become familiar with through experience, and our further task should be to study the properties of the electric field and its laws.

Lecture No. 1. The concept of electric charge. Interaction of charges. Electric field.

Target: provide students with knowledge of the basics of electrostatics.

Task: teach students the basic concepts of electrostatics.

1. Basic concepts about charge.

2. Interaction of charges.

3. Electric field.

Basic concepts about charge

The charge of an electron is the smallest electrical charge known in nature. A charge equal to 6.29 ∙ 10 18 electrons was taken as a unit of charge and called a coulomb. The unit of charge coulomb is written in abbreviation – Cl. The coulomb is a SI (System International) unit.

Charges are divided according to their properties into positive and negative. Like charges repel, unlike charges attract, uncharged objects are attracted to both positively and negatively charged bodies.

Charge interaction

It was experimentally established that the force of interaction between two charges is proportional to the value of these charges and inversely proportional to the square of the distance between them. The formula by which the interaction of charged bodies is calculated is called Coulomb’s law:

F=Q1Q2/є and R 2,

F – force of interaction between charges Q1 and Q2, (Newton).

Q1 and Q2 – charges, Cl.

R – distance between the centers of charged bodies, m;

є a - dielectric constant of the medium, equal to the productє 0 (dielectric constant of vacuum) and є r (dielectric constant of a given medium, shows how many times the interaction of charged bodies decreases if they are transferred from vacuum to given environment), measured in Farad per meter.

Electric field.

The electric field is special kind matter through which the interaction of charges occurs. The electric field of unchanging charges is called electrostatic.

Each point of the electric field is characterized by the electric field strength E. E = F/q, where – F is the force acting on the test charge placed at a given point in the field. A test charge is a charge that is much smaller than the charge creating the main field. Tension is measured in N/C.

Electric field strength – vector quantity, which characterizes the electric field and determines the force acting on a charged particle from the electric field. The electric field is represented by tension lines. The density of the lines is shown to be proportional to the electric field strength. The direction of the field at each point coincides with the direction of the tangent at that point. An electric field whose intensity vectors are the same at all points is called homogeneous.

Lecture No. 2. Potential. Voltage. Electrical capacity. Capacitors.

Target: restore and deepen students’ knowledge on the topic “electric field”.

Task: Learn to determine voltage and capacitance.

1. Concepts of potential and voltage.

2. The concept of electrical capacitance.

Charges distributed on bodies whose dimensions are significantly smaller than the distances between them can be called point, since in this case neither the shape nor the size of the bodies significantly influence the interactions between them.

The interaction of stationary electric charges is called electrostatic or Coulomb interaction. The forces of electrostatic interaction depend on the shape and size of the interacting bodies and the nature of the charge distribution on them.

The force of interaction between two point stationary charged bodies in a vacuum is directly proportional to the product of the absolute values ​​of the charges and inversely proportional to the square of the distance between them:

If bodies are in an environment with dielectric constant , then the interaction force will be weakened by a factor

Forces of interaction between two points stationary bodies directed along the straight line connecting these bodies.

The unit of electric charge in the international system is accepted pendant. 1 C is the charge passing through the cross section conductor at a current of 1 A.

The coefficient of proportionality in the expression of Coulomb's law in the SI system is equal to

Instead, a coefficient called electrical constant

Using electric permanent law the pendant looks like

If there is a system of point charges, then the force acting on each of them is defined as the vector sum of the forces acting on a given charge from all other charges in the system. In this case, the force of interaction of a given charge with a specific charge is calculated as if there were no other charges ( superproposition principle).

1. Electric field. (definition, tension, potential, electric field pattern) Electric field

The interaction of electric charges is explained by the fact that around each charge there is electric field. The electric field of a charge is material object, it is continuous in space and is capable of acting on other electric charges. Electric field stationary charges called electrostatic. The electrostatic field is created only electric charges, exists in the space surrounding these charges and is inextricably linked with them.

The electric field of a charge is a material object, it is continuous in space and is capable of acting on other electric charges. If you bring a charged rod at some distance to the electroscope without touching its axis, the needle will still bow. This is the action of the electric field.

Electric field strength

Charges, being at a certain distance from one another, interact. This interaction is carried out through an electric field. The presence of an electric field can be detected by placing electric charges at various points in space. If the charge at a given point is affected by electric force, then this means that there is an electric field at a given point in space. The strength characteristic of the electric field is tension E. If a charge q 0 located at a certain point is acted upon by a force F, then the electric field strength E is equal to: E=F/q 0 . Graphically force fields depict power lines. A line of force is a line whose tangent at each point coincides with the vector of the electric field strength at that point.

The electric field strength is physical quantity, numerically equal to strength, acting on a unit charge placed in this point fields. The direction of the tension vector is taken to be the direction of the force acting on a point positive charge.

Uniform electric field- this is a field at all points of which the intensity is the same absolute value and direction. The electric field between two oppositely charged metal plates is approximately uniform. Power lines such fields are straight lines of equal density.

If several electric fields act simultaneously on a charge, then the field strength is equal to the vector sum of the strengths of all fields (superposition principle):

ELECTRIC FIELD is:

Physical encyclopedic dictionary. - M.: Soviet encyclopedia. Editor-in-Chief A. M. Prokhorov. 1983.

ELECTRIC FIELD

Vector field that determines the force effect on the charge. particles, independent of their speeds. E. p. is one of the components of a single electromagnetic field.

In electrodynamic in a vacuum, the properties of electrical energy are fully described electric field strength E(t, r).

Force acting on the charge q from E. F=q E. In addition, the moving charge is also acted upon by a force from magnetic field(cm. Lorentz force).

There are potential E r and vortex (solenoidal) E s components E. E=E p+ E s). Source in tens. fields are charges:

where r is the electrical density. charge.

Vortex component E.

Where IN -magnetic induction vector.

With macroscopic description of el.-magn. phenomena in material environments power characteristic The e.p. remains the tension vector E (t, r), which is the result of averaging over a physically small volume and characteristic times of micropulsations of vacuum energy e( E= e>)(see Lorentz - Maxwell equations). Another averaged characteristic of electrical energy in a medium is the vector of electrical induction D (t, r) = E+ 4p P , Where R - electrical density dipole moment environment. Communication between D And E is established by the material level - in general case integral nonlinear relation. In the weak field approximation, when nonlinear effects can be neglected, the material equation has the form

where integration is carried out over the volume of the light cone - complex tensor dielectric constant(a, b=1, 2, 3). For harmonic exp( i w t - i kr )-processes, the material level is simplified:

where the dependences of the dielectric tensor. permeability of the medium e(w, k ) from cyclic frequency с and wave vector k determine the temporal and spatial dispersion of the medium, respectively.

In SI, the induction vector D is also introduced for vacuum: D = e 0 E , where e 0 -electric. vacuum permeability; however, a two-vector description E. M. A. Miller, G. V. Permitin.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-chief A. M. Prokhorov. 1988.

Define electric field strength

Electric field strength- vector physical quantity characterizing the electric field at a given point and numerically equal to the ratio force acting on a stationary point charge, placed at a given point in the field, to the magnitude of this charge:

From this definition it is clear why the electric field strength is sometimes called the force characteristic of the electric field (indeed, the entire difference from the force vector acting on a charged particle is only in a constant factor).

At every point in space at the moment time there is a vector value (generally speaking, it is different in different points space), thus, is a vector field. Formally, this is expressed in the notation

representing the electric field strength as a function of spatial coordinates (and time, since it can change with time). This field, together with the field of the magnetic induction vector, represents an electromagnetic field, and the laws to which it obeys are the subject of electrodynamics.

Electric field strength in International system units (SI) are measured in volts per meter [V/m] or newtons per coulomb [N/C].

Physics. What is an electric field?

Irina Kovalenko

Electric field - special shape matter that exists around bodies or particles with an electric charge, as well as in free form in electromagnetic waves. The electric field is directly invisible, but can be observed by its action and with the help of instruments. The main effect of the electric field is the acceleration of bodies or particles with an electric charge.
The electric field can be considered as mathematical model, describing the value of the electric field strength at a given point in space. Douglas Giancoli wrote: “It should be emphasized that the field is not some kind of substance; it is more correct to say that it is an extremely useful concept ... The question of the “reality” and existence of the electric field is in fact a philosophical, rather even a metaphysical question. In physics, the idea of the field turned out to be extremely useful - it is one of greatest achievements human mind."
The electric field is one of the components of a single electromagnetic field and a manifestation of electromagnetic interaction.
Physical properties of the electric field
At present, science has not yet reached an understanding physical entity fields such as electric, magnetic and gravitational, as well as their interactions with each other. The results have just been described so far. mechanical impact on charged bodies, and there is also a theory electromagnetic wave, described by Maxwell's Equations.
Field effect - The field effect is that when an electric field is applied to the surface of an electrically conducting medium, the concentration in its near-surface layer changes free media charge. This effect underlies the operation of field-effect transistors.
The main effect of the electric field is the force effect on stationary (relative to the observer) electrically charged bodies or particles. If a charged body is fixed in space, then it does not accelerate under the influence of force. The magnetic field (the second component of the Lorentz force) also exerts a force on moving charges.
Observing the electric field in everyday life
In order to create an electric field, it is necessary to create an electric charge. Rub some dielectric on wool or something similar, such as a plastic pen on your own hair. A charge will be created on the handle, and an electric field will be created around it. A charged pen will attract small pieces of paper. If you rub a larger object, such as a rubber band, on the wool, then in the dark you will be able to see small sparks caused by electrical discharges.
An electric field often occurs near the television screen when the television receiver is turned on or off. This field can be felt by its effect on the hairs on the hands or face.

Spacewolf

Electric field
private form of manifestation (along with magnetic field) electromagnetic field, which determines the effect on an electric charge of a force that does not depend on the speed of its movement. The concept of electromagnetic energy was introduced into science by M. Faraday in the 30s. 19th century According to Faraday, each charge at rest creates an electron field in the surrounding space. The field of one charge acts on another charge, and vice versa; This is how charges interact (the concept of short-range interaction). The main quantitative characteristic of electrical energy is the electric field strength E, which is defined as the ratio of the force F acting on the charge to the charge value q, E = F/q. The electrical energy in a medium, along with tension, is characterized by the vector of electrical induction (see Electrical and magnetic induction). The distribution of electrical energy in space is clearly depicted using the field lines of electrical energy intensity. The field lines of potential electrical energy generated by electric charges begin at positive charges and end in negative. The lines of force of the vortex electron generated by an alternating magnetic field are closed.

Alexander Kretov

These are words that people came up with to explain the interaction of certain objects.
By the way, they came up with a very successful idea: you can draw conclusions, build theories, and all this is confirmed in practice.
P.S. I am very glad that people know how to actively use reference books. This is useful!

Studying the mechanism of interaction of charges, scientists have long assumed the presence of an electric field. It has long been known that there is no direct interaction of electric charges with each other. A field is created around each charge, through which the electric charges act on each other. As you move away from the charge, the effect of the field begins to weaken.

What is an electric field

The electric field is not perceived by ordinary senses; it is determined only by its effect on electric charges. The consequences of these interactions can be determined using instruments, which means that the electric field has a material basis. It does not get stuck at any one point, but exists in certain space. Its presence is determined by the appearance of a certain force acting on a particular electric charge.

An electric field is a manifestation of a special form of matter surrounding bodies that have electric charges. If a charge is placed at any point in the field, it will experience a force. In order to actually determine the presence or absence of a field, it is necessary to place as many more charges. How larger number located in one place, so more chances For measuring instruments, register the electric field.

Electric field properties

The main property is the ability to influence electric charges with a certain force. Based on this effect, all the characteristics of the electric field are studied.

The electric field itself is part of the general electromagnetic field. Therefore, el. The field can be created not only with the help of electric charges, but also under the influence of alternating magnetic fields. However, an electrostatic field, constant in time, can only be created under the influence of stationary charges.

The existence of an electric field must be confirmed by certain quantitative characteristics. Such characteristics allow us to compare different fields with each other and study their properties more deeply. The main characteristic is the force acting on electric charges at any point in this field. Thus, the electric field is a quantity that is completely amenable to material measurement and study.