Explain why uncharged bodies are attracted to charged ones. Why are uncharged bodies attracted to charged ones? Purpose of the lesson for the teacher

Electric field

1 Electric charge

Electromagnetic interactions are among the most fundamental interactions in nature. The forces of elasticity and friction, the pressure of liquid and gas, and much more can be reduced to electromagnetic forces between particles of matter. Electromagnetic interactions themselves are no longer reduced to other, deeper types of interactions. Equally fundamental type interaction is gravitation - the gravitational attraction of any two bodies. However, there are several important differences between electromagnetic and gravitational interactions.

1.Not any, but only charged bodies (having electric charge).

2.Gravitational interaction is always the attraction of one body to another. Electromagnetic interactions can be either attractive or repulsive.

3. Electromagnetic interaction is much more intense than gravitational interaction. For example, the force of electrical repulsion between two electrons is 10 42 times greater than the force of their gravitational attraction to each other.

Each charged body has a certain amount of electric charge q. Electric charge is physical quantity, which determines the strength of the electric magnetic interaction between natural objects. The unit of charge is the coulomb (C).

1.1 Two types of charge

Since gravitational interaction is always attraction, the masses of all bodies are non-negative. But this is not true for charges. Two types electromagnetic interaction- attraction and repulsion - it is convenient to describe by introducing two types of electrical charges: positive and negative.

Charges of different signs attract each other, and charges of the same sign repel each other. This is illustrated in Fig. 1; The balls suspended on threads are given charges of one or another sign.

Rice. 1. Interaction of two types of charges

The widespread manifestation of electromagnetic forces is explained by the fact that the atoms of any substance contain charged particles: the nucleus of an atom contains positively charged protons, and negatively charged electrons move in orbits around the nucleus. The charges of a proton and an electron are equal in magnitude, and the number of protons in the nucleus is equal to the number of electrons in orbits, and therefore it turns out that the atom as a whole is electrically neutral. That's why under normal conditions we don't notice electromagnetic influence from others ( The charge unit is determined through the current unit. 1 C is the charge passing through cross section conductor in 1 s at a current of 1 A.) bodies: the total charge of each of them equal to zero, and charged particles are evenly distributed throughout the volume of the body. But if electrical neutrality is violated (for example, as a result of electrification), the body immediately begins to act on the surrounding charged particles.

Why are there exactly two types of electric charges, and not some other number of them, in at the moment not known. We can only assert that accepting this fact as primary provides an adequate description of electromagnetic interactions.

The charge of a proton is 1.6 · 10 −19 C. The charge of the electron is opposite in sign and equal to −1.6 · 10 −19 C. The value e = 1.6 10 −19 C is called elementary charge. This is the minimum possible charge: free particles with a smaller charge were not detected in the experiments. Physics cannot yet explain why nature has the smallest charge and why its magnitude is exactly that.

The charge of any body q always consists of the whole quantities elementary charges: q = ± Ne. If q< 0, то тело имеет избыточное количество N электронов (по сравнению с количеством протонов). Если же q >0, then, on the contrary, the body lacks electrons: there are N more protons.

1.2 Electrification of bodies

In order for a macroscopic body to exert electrical influence to other bodies, it must be electrified. Electrification is a violation of the electrical neutrality of the body or its parts. As a result of electrification, the body becomes capable of electromagnetic interactions.

One of the ways to electrify a body is to impart an electric charge to it, that is, to achieve an excess of charges of the same sign in a given body. This is easy to do using friction.

Thus, when a glass rod is rubbed with silk, part of its negative charges goes to the silk. As a result, the stick becomes positively charged and the silk negatively charged. But when rubbing an ebonite stick with wool, some of the negative charges are transferred from the wool to the stick: the stick is charged negatively, and the wool is charged positively.

This method of electrifying bodies is called electrification by friction. You experience electrifying friction every time you take a sweater off over your head.

Another type of electrification is called electrostatic induction, or electrification through influence. In this case, the total charge of the body remains equal to zero, but is redistributed so that positive charges accumulate in some parts of the body, and negative charges in others.

Rice. 2. Electrostatic induction

Let's look at fig. 2. At some distance from metal body there is a positive charge q. It attracts negative charges of the metal ( free electrons), which accumulate on the areas of the body surface closest to the charge. On distant areas uncompensated positive charges remain.

Despite the fact that the total charge of the metal body remained equal to zero, a spatial separation of charges occurred in the body. If we now divide the body along the dotted line, then right half will be negatively charged, and the left one will be positively charged. You can observe the electrification of the body using an electroscope. A simple electroscope is shown in Fig. 3.

Rice. 3. Electroscope

What's happening in in this case? A positively charged stick (for example, previously rubbed) is brought to the electroscope disk and collects a negative charge on it. Below, on the moving leaves of the electroscope, uncompensated positive charges remain; pushing away from each other, the leaves diverge into different sides. If you remove the stick, the charges will return to their place and the leaves will fall back.

The phenomenon of electrostatic induction on a grand scale is observed during a thunderstorm. In Fig. 4 we see a thundercloud passing over the earth.

Rice. 4. Electrification of the earth by a thundercloud

There are pieces of ice inside the cloud different sizes, which are mixed by rising air currents, collide with each other and become electrified. It turns out that a negative charge accumulates in the lower part of the cloud, and a positive charge accumulates in the upper part.

The negatively charged lower part of the cloud induces charges below it on the surface of the earth positive sign. A giant capacitor appears with a colossal voltage between the cloud and the ground. If this voltage is sufficient to breakdown the air gap, then a discharge will occur - the well-known lightning.

1.3 Law of conservation of charge

Let's return, for example, to electrification by friction - rubbing a stick with a cloth. In this case, the stick and the piece of cloth acquire charges equal in magnitude and opposite in sign. Their total charge was equal to zero before the interaction and remains equal to zero after the interaction.

We see here the law of conservation of charge, which states: closed system tel algebraic sum charges remains unchanged during any processes occurring with these bodies:

q1 + q2 + . . . + qn = const.

The closedness of a system of bodies means that these bodies can exchange charges only among themselves, but not with any other objects external to this system.

When electrifying a stick, there is nothing surprising in the conservation of charge: how many charged particles left the stick, the same amount came to the piece of fabric (or vice versa). What's surprising is that in more complex processes, accompanied mutual transformations elementary particles and by changing the number of charged particles in the system, the total charge is still conserved! For example, in Fig. Figure 5 shows the process γ → e − + e +, in which a portion electromagnetic radiationγ (the so-called photon) turns into two charged particles - an electron e - and a positron e +. Such a process turns out to be possible under certain conditions - for example, in the electric field of the atomic nucleus.

Rice. 5. Birth of an electron–positron pair

The charge of a positron is equal in magnitude to the charge of an electron and opposite in sign. The law of conservation of charge is fulfilled! Indeed, at the beginning of the process we had a photon whose charge was zero, and at the end we received two particles with a total charge of zero.

The law of conservation of charge (along with the existence of the smallest elementary charge) is primary today scientific fact. Physicists have not yet been able to explain why nature behaves this way and not otherwise. We can only state that these facts are confirmed by numerous physical experiments.

2 Coulomb's Law

Interaction of motionless ones (in this inertial system counting) charges is called electrostatic. It is the easiest to learn.

The branch of electrodynamics in which interaction is studied stationary charges, is called electrostatics. The fundamental law of electrostatics is Coulomb's law.

By appearance Coulomb's law is surprisingly similar to the law universal gravity which establishes the character gravitational interaction point masses. Coulomb's law is the law of electrostatic interaction of point charges.

Point charge- this is a charged body, the dimensions of which are much smaller than other dimensions characteristic of this problem. In particular, the sizes of point charges are negligible compared to the distances between them.

A point charge is the same idealization as material point, point mass, etc. In the case of point charges, we can unambiguously talk about the distance between them, without thinking about exactly between which points of charged bodies this distance is measured.

Coulomb's law. The force of interaction between two stationary point charges in a vacuum is directly proportional to the product absolute values charges and is inversely proportional to the square of the distance between them.

This force is called Coulomb. Vector Coulomb force always lies on the straight line that connects the interacting charges. For the Coulomb force, Newton's third law is valid: charges act on each other with forces equal in magnitude and opposite in direction.

As an example in Fig. Figure 6 shows the forces F1 and F2 with which two negative charges interact.

Rice. 6. Coulomb force

If charges equal in magnitude to q1 and q2 are located at a distance r from each other, then they interact with the force

The proportionality coefficient k in the SI system is equal to:

k = 9 10 9 N m 2 /Cl 2.

If we compare it with the law of universal gravitation, then the role of point masses in Coulomb’s law is played by point charges, and instead of the gravitational constant G there is a coefficient k. Mathematically, the formulas of these laws are structured identically. An important physical difference is that the gravitational interaction is always attractive, while the interaction of charges can be either attractive or repulsive.

It just so happens that along with the constant k there is another fundamental constantε 0 related to k by the relation

The constant ε 0 is called the electrical constant. It is equal to:

ε 0 = 1/4πk = 8.85 10 −12 C 2 /N m 2.

Coulomb's law with electric constant looks like this:

Experience shows that the so-called superposition principle is fulfilled. It consists of two statements:

1. The Coulomb force of interaction between two charges does not depend on the presence of other charged bodies.
2. Let us assume that charge q interacts with the system of charges q1, q2, . . . , qn. If each of the charges of the system acts on charge q with a force F1, F2, . . . , Fn, respectively, then the resulting force F applied to the charge q by the given system is equal to the vector sum of the individual forces:

F = F1 + F2 + . . . +Fn

The principle of superposition is illustrated in Fig. 7. Here the positive charge q interacts with two charges: positive charge q1 and negative charge q2.

Rice. 7. Superposition principle

The principle of superposition allows us to arrive at one important statement.

You remember that the law of universal gravitation is actually valid not only for point masses, but also for balls with a spherically symmetric mass distribution (in particular, for a ball and a point mass); then r is the distance between the centers of the balls (from the point mass to the center of the ball). This fact follows from mathematical form the law of universal gravitation and the principle of superposition.

Since the formula of Coulomb's law has the same structure as the law of universal gravitation, and the principle of superposition is also satisfied for the Coulomb force, we can draw a similar conclusion: according to Coulomb’s law, two charged balls will interact (a point charge with a ball), provided that the balls have a spherically symmetric charge distribution; the value r in this case will be the distance between the centers of the balls (from the point charge to the ball).

Significance this fact we will see very soon; in particular, this is why the field strength of a charged ball outside the ball will be the same as that of a point charge. But in electrostatics, unlike gravity, one must be careful with this fact. For example, when positively charged metal balls come together spherical symmetry will be violated: the positive charges, mutually repelling, will tend to the areas of the balls that are most distant from each other (the centers of the positive charges will be further from each other than the centers of the balls). Therefore, the repulsive force of the balls in this case will be less than the value that is obtained from Coulomb’s law when substituting the distance between the centers instead of r.

2.2 Coulomb's law in a dielectric

The difference between electrostatic interaction and gravitational interaction is not only the presence of repulsive forces. The force of interaction of charges depends on the medium in which the charges are located (and the force of universal gravity does not depend on the properties of the medium). Dielectrics, or insulators are substances that do not conduct electric current.

It turns out that the dielectric reduces the force of interaction between charges (compared to vacuum). Moreover, no matter what distance the charges are located at from each other, the force of their interaction in a given homogeneous dielectric will always be the same number of times less than at the same distance in vacuum. This number is denoted ε and is called the dielectric constant of the dielectric. Permittivity depends only on the substance of the dielectric, but not on its shape or size. It is a dimensionless quantity and can be found from tables. Thus, in a dielectric, formulas (1) and (2) take the form:

The dielectric constant of vacuum, as we see, is equal to unity. In all other cases, the dielectric constant is greater than unity. The dielectric constant of air is so close to unity that when calculating the forces of interaction between charges in the air, formulas (1) and (2) for vacuum are used.

Newton believed that gravity spreads instantly, gravitation is akin to electrical interaction, light has corpuscular nature, exists absolute environment propagation of light - ether, acceleration is of an absolute nature, manifesting itself in absolute space.

At the beginning of the century, the revision of such views was completed. The ether is replaced by empty space, in which three coordinates are supplemented by time. Einstein modeled gravity using matrix mathematics as the curvature of space-time, and considered inertia as special case equivalence of gravity. The absolute nature of the acceleration has disappeared, thereby calling into question the possibility of determining the trajectory of movement through the acceleration function, contrary to well-known practice.

Let's try to give gravity some physical meaning. Let us make the assumption that in Nature the basis of interaction is electrical forces that obey Coulomb’s law. It is known that if a medium - an insulator (dielectric) is placed between the charges of electricity, then the associated charges of the dielectric will undergo spatial polarization - to positive charge the negative parts will be turned towards the negative, and the positive parts of the bound charges will turn towards the negative. Moreover, for relatively weak charges placed in a medium, the bound charges will remain undestroyed; with strong charges, their destruction will occur and an electrical “breakdown” will occur. Let's consider three possible cases in electrical interactions.

1. There are two charges. Between them there is a medium polarized by them. Polarization is organized as follows: with charges of the same sign, the medium of polarized charges will experience self-repulsion according to Coulomb’s law, which will integrally manifest itself as the repulsion of two charges; with unlike charges, the medium of polarized charges will experience self-attraction according to Coulomb’s law, forming an attractive force of two unlike charges.
2. There is one charge and an uncharged object. The charge will also cause a polarization of the medium, which will quite naturally cause a reciprocal polarization of the uncharged object so that the medium forms an attraction of the uncharged body to the charge. In other words, there are electrical forces of attraction between charged and uncharged bodies. It would seem that this case contradicts Coulomb's law. However, experience confirms the existence of an attractive force between charged and uncharged bodies. Everyone can repeat the experiment of Thales, done by him more than 2500 years ago: rub an insulating stick on woolen material and bring it to light objects(scraps of dry paper, for example). Uncharged objects will be attracted to the wand. When friction occurs, the material “breaks” outer electrons atoms of the stick - it is electrified with static electricity.
3. There are two uncharged objects located in a dielectric medium. They experience the only gravitational attraction possible in this case. How can this phenomenon be explained using electrical forces? This can only be accomplished if we make the assumption that the medium itself has a very weak “gravitational” electrical charge. Let us extend this assumption to all bodies in Nature. Then the mutual polarization of bodies and the medium between them will cause self-attraction in the medium, which forms gravity, even if there is a weak gravitational electric charge of the same sign on all bodies and the medium. This occurs due to the phenomenon of polarization (Coulomb's law), which is "redistributed" so that only attractive forces are present. Each reader can draw on paper a diagram of mutual polarization, based on the assumption that the associated charges of both bodies and media have a certain excess of charge of one sign over the charge of the other sign and detect the force of “gravity”.

Thus, it was possible to draw a physical picture of gravity. This was not available either for Newton’s law, or for Einstein’s theory of gravity (GTR), or for Logunov’s relativistic theory of gravity (RTG). The situation is even simpler with inertia, which also cannot be explained in the traditional way adopted in GTR and RTG. Any electric charge moving with acceleration experiences a counterforce akin to the extra current of closure and opening, in which the carriers of the electric charge are accelerated or decelerated.

The emergence of magnetism is closely related to changes in electricity, and, conversely, with changes in magnetism, electricity, or rather its current, is excited. It is known that magnetic monopoles, displayed in another Coulomb formula for magnetic interaction, have not yet been found. Neutrons and protons, which are part of nuclei more complex than the hydrogen nucleus, have magnetic moments. In other words, the constituent parts of the nucleus have the property of magnetic dipoles - they are simply tiny magnets. Coulomb's law is not suitable for identifying the interaction between magnetic dipoles, but the law of their interaction can be established experimentally: to do this, you need to take two ordinary magnets and measure the strength of their interaction as a function of the distance between them on a torsion (as Coulomb did) or lever scales. A priori, it can be argued that at close distances the force of interaction will not be determined by the law of inverse squares of distances, but will obey the law not of long-range action, but of short-range action. Indeed, with increasing distance magnetic dipole will acquire the properties of a body that has no noticeable division magnetic poles. At close distances, unusually large forces are required to separate or connect two magnets, depending on their mutual magnetic polarity. It is known that nuclear interactions about 1000 times stronger than strength electromagnetism. It is natural to assume that magnetic dipole moments may be the source strong interaction in the structure of the nuclei of matter. This paragraph has taken our discussion somewhat off topic, but it is of fundamental importance in the statement about the fundamental role of electricity in Nature.

So, the introduction of the environment and the weak gravitational electric charge of the environment and all material bodies made it possible to draw a physical picture of gravitational interaction and explain the phenomenon of inertia. What else can be learned from such an environment?

Let's turn to the light as electromagnetic phenomenon. In the source, either from heating or from the generator, there is intense movement of real charges (electrons, ions, etc.) in the source material. Bound charges of the medium, interacting with the charge carriers of the source, will be drawn into motion according to Coulomb’s law: for example, the electron of the source, oscillating, will involve in parallel motion the polarized charge of the medium, oriented with its positive part closer to the electron, and its negative part further away from the source electron. This process will be repeated many times by those closest to the first bound charge in the chain of bound charges of the medium. Formed lateral movement polarized charges, called displacement current by Maxwell. Each successive displacement current will have the opposite direction to the previous current, since the charges of the carriers of these currents are opposite in sign and identical in the direction of movement. The magnetic fields of such parallel displacement currents are summed up. When the direction of movement of the “first” electron of the source changes, the direction of the displacement currents changes, at which the direction also changes magnetic field. There is a “slowdown” in the propagation speed transverse vibrations environment according to the laws of extracurrents. The speed of propagation of electromagnetic disturbances in the medium turns out to be limited and constant, independent of the source and depending only on the electrical and magnetic properties of the medium.

These properties are designated in physics in the form of electric and magnetic permeability. We obtained a physical picture of the radiation and propagation of an electromagnetic disturbance, which in ordinary physics is called an electromagnetic wave. In fact, in the usual sense electromagnetic wave no, just like there is no photon, but there is a “retransmission” of the movement of the source charges, like a formation of falling dominoes. What then is the propagation of the gravitational front or, as they call it in physics, “ gravitational wave"? A natural assumption is that the front of gravity propagation is a longitudinal, limited in amplitude, movement of bound charges of the medium. The source of the gravitational front can be the eruption of masses from something in which there was no substance before, rapid movement space objects in the environment, etc.

In “black holes” at the boundary of the “event horizon,” the polarization deformation reaches its strength limit and a certain layer of the medium is destroyed. This phenomenon is called in physics as “evaporation of black holes.” Coordinated movement of displaced charges, in which polarization is directed along a line normal to the surface space object, is accompanied by coordinated displacement currents of like charges occurring in the same direction. In this case, the resulting magnetic field between the currents is compensated to zero, and the magnetic field around all displacement currents is summed up. However, the gravitational polarization of the medium has a “central” structure in space, which leads to complete absence"braking" magnetic field. This, in turn, leads to an almost endless high speed transmission of gravity in contrast to the speed of propagation of electromagnetic disturbance. The time it takes for gravity to propagate from the edge to the edge of our Universe is 100 orders of magnitude less than Planck’s time! Near massive objects, black holes, thanks to high density polarization of the environment, the speed of propagation of gravity and light decreases, which is usually interpreted as time dilation in the theory of general relativity.

The idea of ​​the existence of a medium capable of polarization (electrical deformation) leads to the modeling of the well-known “photoeffect” in physical vacuum(PV), in which an electromagnetic disturbance with a frequency exceeding the “red frequency limit” knocks out, for example, an electron-positron pair from the medium. According to Lamb's ideas (1947), the medium introduces a certain difference in the transition distances of the electrons of hydrogen and deuterium atoms, which is responsible for the fine structure of the radiation. Constant fine structure(number 137) receives new interpretation as the number of elementary charges involved in the interactions of electromagnetic disturbances with the environment. The physical meaning of “uncertainty and probabilistic nature trajectories of elementary particles" in the microworld.

A new interpretation is given to the picture of some cosmological problems of our Universe due to the combination of Coulomb self-repulsion of a charged medium (Big Bang) and Coulomb attraction charged environment in the presence of ordinary matter.

Let's summarize. The introduction of a medium or PV into physics is the key that can open new physics in the 21st century. It will not be based on empty space in which mathematical features and the so-called “material” physical fields, but in a real PV environment, which, according to many scientists, has unlimited “reserves” of energy. They are somewhat difficult to use existing theories empty space of our Universe.

Coulomb's law shows that the force of electrical interaction occurs only between two charged bodies. Indeed, if we put in formula (10.1), then for any value of . We know, however, that a charged body (for example, a rubbed stick of sealing wax) is capable of attracting non-electrified bodies, for example, pieces of paper (Fig. 21) or metal foil.

Rice. 21. Attraction of uncharged pieces of paper to charged wax

We place a paper or metal arrow on a point mounted on an insulating stand so that the arrow can easily rotate on the point. If a charged body is placed near such an arrow, it will immediately turn so that its axis is directed towards the charged body (Fig. 22). By turning the arrow with our hand and releasing it again, we will find that it returns to its previous position. Which end of the arrow turns out to be facing the charged body is a matter of chance, but the arrow never stops so that its axis makes a noticeable angle with the direction of the charged body.

Rice. 22. A charged body acts on an uncharged arrow made of metal or paper, turning it

To explain these interactions between charged and uncharged bodies, we need to recall the phenomenon of induction (§8) and Coulomb's law (§10). All bodies (pieces of paper, arrows) near a charged body experience electrification through influence (induction), as a result of which the charges present in these bodies are redistributed so that excess charges of one sign accumulate in one part of the body, and of another sign in another (Fig. 23 and 24).

Rice. 23. Explanation of the attraction of uncharged pieces of paper by charged sealing wax

Rice. 24. Explanation of the action of a charged body on an uncharged arrow

In this case, closer to the influencing charged body are charges whose sign is opposite to the sign of its charge; charges of the same name accumulate in excess at the distant end. The interaction of a body charge with induced (induced) charges occurs according to Coulomb’s law. Therefore, every body with induced charges is simultaneously attracted and repelled by a charged body. But the repulsion that occurs between charges located on greater distance, weaker than gravity. As a result, “uncharged” bodies turn and are attracted by a charged body, as is observed experimentally.

Lesson plan:

1. Summarize previously acquired knowledge about the electrification of bodies based on electron theory.
2. Group and individual work:

• working with dough;
• Create mini projects “Using and combating static electricity.”

3. Mini-conference on project protection.
4. Lesson summary.
5. Homework.

On the board.

Objective of the lesson for the teacher:

Systematize and generalize students’ knowledge about the electrification of bodies. Based on electronic theory, explain the process of electrification of bodies.

Tasks for the teacher:

• creating conditions that awaken students’ self-educational activity;
• continue to develop observation skills physical phenomena, test theoretical positions using experiment, use instruments;
• focus on the need to comply with safety regulations to prevent fires and accidents at work and at home.

For students:

Purpose of the lesson: recall the concepts of electric charge and its properties; explain the phenomenon of electrification; consider the practical orientation of the acquired knowledge.

Tasks:

1. Educational:

• Based on electronic theory, explain the process of electrification of bodies;
• Studying the practical orientation of the acquired knowledge;
• Formation of motivation and experience of educational, cognitive and practical activities.

2. Developmental:

• To promote the development of the ability to analyze, put forward hypotheses, assumptions, make forecasts, observe and experiment;
• Promote development logical thinking;
• Development of the ability to express in speech the results of one’s own mental activity.

3. Educational:

• contribute to the formation of a scientific worldview;
• wake cognitive interest to the subject and surrounding phenomena;
• development of abilities for cooperation, communication, teamwork;
• to develop the ability to critically but objectively evaluate objects, phenomena, actions and actions (one’s own and others’).

Methodical: show the possibility of practical application of knowledge acquired in physics lessons.

Methods and techniques:

1. Methods of verbal transmission of information and auditory perception of information (techniques: conversation, story, discussion);
2. Methods for visually conveying information and visual perception information (techniques: observation, demonstration of experience, presentation);
3. Methods of transmitting information using practical activities and tactile kinesthetic perception ( experimental work in groups);
4. Methods of stimulating and motivating students (techniques: creating problematic situation, problematic presentation, partial search activity, group research activity, creating a situation of success, creating a situation of mutual assistance);
5. Control methods (techniques frontal survey, testing, self-assessment).

Principles: scientific character, consistency, conformity with nature, accessibility, personal development, collectivism.

Learning Tools:

• PC, projector, screen;
• electrometers, plexiglass and ebonite sticks, woolen scraps, a conductor, plastic and metal funnels, a tripod, a plexiglass plate, a transparent plastic box with pepper.
• worksheets, cards for recording the activity of work in the lesson, forms of supporting notes.

Progress of the lesson.

Hello.

Today in class we will:

• Summarize previously acquired knowledge about the electrification of bodies based on electronic theory;
• Work with the dough;
• Create mini-projects about the benefits and harms of electricity. And hold a mini-conference to protect projects.

Open your notebooks and write down the topic of the lesson. "Explanation electrical phenomena” (sl. No. 1) . So the main task of our lesson based on knowledge about the electron and the structure of the atom, give an explanation of the electrification of bodies upon contact, the existence of conductors and dielectrics, as well as explain the attraction of uncharged conductors (bodies) to charged bodies.

I. Updating knowledge.

But first, let's remember a number of provisions arising from the electronic theory.

1. What are all bodies made of? ( atoms) sl. №2 (1)
2. What is the structure of an atom? ( a positive nucleus consisting of protons and neutrons, electrons move around the nucleus and can leave their shells) sl. №2 (2)
3. What is the charge of an electron? (negative) sl. №2 (3)
4. What is the charge of a proton? (positive) sl. №2 (4)
5. Then it turns out that all bodies are initially charged. (Under what condition is the body uncharged)
6. Under what condition will the body be positively charged?
7. Under what condition will the body be negatively charged?
8. Therefore, a body becomes charged when it gains or loses electrons.
9. Slide No. 3 (1), next. No. 3 (2) What sign is the ebonite stick charged with? What kind of wool? (questions on the slide)
10. Electrons are transferred from the wool to the ebonite rod.
11. Therefore, charges are not created, but only separated.
12. Why do electrons move from wool to ebonite, and not vice versa?

II. Explanation of the phenomenon of attraction of an uncharged body to a charged one.

13. Look at the picture and answer, is the ball charged? If charged, what sign does the ball have? Justify your answer.
14. An electric field acts only on a charged body.
15. Experience with an unloaded cartridge case. Why was the unloaded cartridge first attracted and then began to be repelled?

And so we remembered a number of provisions arising from the electronic theory and gave them an explanation. We also found out why an uncharged body is first attracted to a charged body and then repelled from it.

III. Work in groups and individually.

Our further work will proceed as follows. Now we will form 4 groups of researchers who will start working on projects, each group will carry out its own project with its own specific topic. But they are all consonant with the theme of our conference “The use of static electricity and the fight against it.” 2 groups are doing projects that prove that static electricity can serve humans, and 2 groups are doing projects that prove that static electricity can cause harm and will tell you how to deal with it.

The rest of the guys sit down at the computers to complete the screening test.

• I explain how to work with the test;
• I'm going to the research groups. The work takes place within 12 minutes. Then everyone sits down and the projects are defended.

IV. Protecting projects (10 minutes)

And now I invite everyone to the conference “The use of static electricity and the fight against it.”

We are constantly in an ocean of electrical discharges created by numerous machines, machine tools and man himself. These discharges, of course, are not as powerful as natural lightning, so we don’t notice them, except for the slight pricks that we sometimes experience when we touch a metal object or another person with our hand. But such categories exist and can, just like big zippers, cause fires and explosions, lead to significant losses, damages and injuries if we do not know why they occur and how to protect ourselves from them.

And the guys who carried out projects on the dangers of static electricity will tell us how to protect ourselves from them. ( defense of projects is heard) Application

But statistical electricity can serve a person. Let's hear the defense of projects on this issue. (defense of projects is heard) Appendix 10, 11.

Thank you very much!

And so today, guys, we once again remembered the structure of the atom, what charges exist in nature, how they interact, explained the electrification of bodies based on electronic theory, and completed 4 projects on the benefits and harms of statistical electricity.

V. Homework.

We may not see each other again, so I give you the task of being in the area of ​​negative ions more often, which will attract “positive” people to you in communication with whom you will receive a positive mood and positive emotions, such as those that I acquired when communicating with you . I thank you for the lesson. I wish you good luck in the next lessons. Goodbye!