Secrets of electrification of bodies. Electrification of bodies upon contact

Physics! What a capacity of words!
Physics is not just sound for us!
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All sciences without exception!

• explain to students the mechanism of electrification of bodies,
• develop research and creative skills,
• create conditions for increasing interest in the material being studied,
• to help students comprehend the practical significance, usefulness of the acquired knowledge and skills.

Equipment:

• electric machine,
• electrometer,
• sultans,
• ebonite and glass sticks,
• silk and woolen fabrics,
• electroscope,
• connecting wires, distilled water, paraffin beads,
• aluminum and paper cylinders, silk threads (dyed and undyed).

On the desk: Conductors, insulators, resin and glass charges.

DURING THE CLASSES

1. Introductory speech of the teacher

In everyday life, a person observes a huge number of phenomena and, perhaps, a much larger number of phenomena go unnoticed.

The existence of these phenomena "pushes" a person to search for them, discover and explain these phenomena. Such a phenomenon as the fall of bodies to the ground in a person does not cause any surprise. But, it should be noted that the earth and the given body interact without touching each other. They interact with each other by the most famous action - gravitational attraction (gravitational fields). We are accustomed to the fact that the bodies act on each other, mostly directly. There are also such phenomena, known to the ancient Greeks, which each time arouse interest in children and adults. These are electrical phenomena.

Examples of electrical interactions are very diverse and are not as familiar to us from childhood as, for example, the attraction of the Earth. This interest is also explained by the fact that here we have great opportunities for creating and changing experimental conditions, making do with simple equipment.

Let us follow the course of revealing and studying some phenomena.

2. Historical background (student reports)

Greek philosopher Thales of Miletus, who lived from 624-547. BC, discovered that amber, worn on fur, acquires the property of attracting small objects - fluffs, straws, etc. Later, this phenomenon was called electrification.

In 1680, the German scientist Otho von Guericke built the first electric machine and discovered the existence of electric forces of repulsion and attraction.

The first scientist who reasonably defended the point of view about the existence of two types of charges was the Frenchman Charles Dufay (1698–1739). The electricity that appears when rubbing resin, Dufay called resin, and the electricity that appears when rubbing glass - glass. In modern terminology, “tar” electricity corresponds to negative charges, and “glass” electricity to positive. The most convincing opponent of the theory of the existence of two types of charges was the famous American Benjamin Franklin (1706 - 1790). He first introduced the concept of positive and negative charges. He explained the presence of these charges in bodies by an excess or deficiency in the bodies of some common electrical matter. This special matter, later called the “Franklin fluid”, in his opinion, had a positive charge. Thus, when electrified, the body either acquires or loses positive charges. It is not difficult to guess that Franklin confused positive charges with negative ones and the bodies exchange electrons (which carry a negative charge). Largely due to this fact, the direction of movement of a positive charge was subsequently mistaken for the direction of the current in metals.

The Englishman Robert Simmer (1707 - 1763) drew attention to the unusual behavior of his woolen and silk stockings. He wore two pairs of stockings: black wool for warmth and white silk for beauty. Taking off both stockings at once and pulling one from the other, he watched both stockings swell, taking the shape of the leg and being attracted to each other. However, stockings of the same color repelled each other, while stockings of different colors attracted each other. Based on his observations, Simmer became a zealous believer in the two-charge theory, earning him the nickname "bloated philosopher."

In modern terms, his silk stockings had negative charges, while his wool stockings had positive charges.

3. The phenomenon of electrization of bodies

Teacher: What body is called charged?

Student: If a body can attract or repel other bodies, then it has an electric charge. Such a body is said to be charged. Charge is a property of bodies, is the ability for electromagnetic interaction.

(Demonstration of the action of a charged body).

Teacher: What is an electroscope?

Student: A device that allows you to detect the presence of a charge in a body and evaluate it is called an electroscope.

Teacher: How does an electroscope work?

Student: The main part of the electroscope is a conductive insulated rod, on which an arrow is fixed, which can rotate freely. When a charge appears, the arrow and the rod are charged with charges of the same sign and therefore, repelling, they create a deflection angle, the value of which is proportional to the charge received.

(Demonstration of the operation of the device).

Teacher: The electrification of bodies can occur in various cases, i.e. There are various ways of electrifying bodies:

• friction
• blow,
• contact
• influence,
• under the influence of light energy.

Let's consider some of them.

Student: If rub an ebonite stick on wool, then the ebonite will receive a negative charge, and the wool will receive a positive charge. The presence of these charges is detected using an electroscope. To do this, touch the rod of the electroscope with an ebonite stick or a woolen rag. In this case, part of the charge of the test body passes to the rod. By the way, in this case, a short-term electric current occurs. Consider the interaction of two paper shells suspended on a thread, one charged from an ebonite stick, the other from a woolen cloth. Note that they are attracted to each other. This means that bodies with opposite charges attract each other. Not every substance can transfer electrical charges. Substances through which charges can be transferred are called conductors, and substances through which charges cannot be transferred are called non-conductors - dielectrics (insulators). This can also be found out with the help of an electroscope, connecting it with a charged body, substances of various kinds.

A white silk thread does not conduct a charge, but a dyed silk thread does. (Fig. A)

White silk thread Dyed silk thread

Separation of charges and the appearance of a double electric layer at the points of their contact, any two different bodies, insulators or conductors, solids, liquids or gases. Describing the electrification by friction, we always took for the experiment only good insulators - amber, glass, silk, ebonite. Why? Because in insulators the charge remains at the place where it originated and cannot pass through the entire surface of the body to other bodies in contact with it. The experiment fails if both rubbing bodies are metals with insulated handles, since we cannot separate them from each other at once over the entire surface.

Due to the inevitable roughness of the surface of bodies, at the moment of separation there always remain some last points of contact - “bridges”, through which all excess electrons escape at the last moment and both metals turn out to be uncharged.

Teacher: Now consider electrification by contact.

Student: If we immerse a paraffin ball in distilled water and then take it out of the water, then both the paraffin and the water will be charged. (Fig.B)

The electrification of water and paraffin occurred without any friction. Why? It turns out that when electrified by friction, we only increase the contact area and reduce the distance between the atoms of rubbing bodies. In the case of water - paraffin, any roughness does not interfere with the convergence of their atoms.

This means that friction is not a prerequisite for the electrization of bodies. There is another reason why electrification occurs in these cases.

Student: The work of the electrophore machine is based on the electrification of the body through influence. An electrified body can interact with any electrically neutral conductor. When these bodies approach each other, due to the electric field of a charged body, a redistribution of charges occurs in the second body. Closer to the charged body are charges opposite in sign to the charged body. Further from the charged body in the conductor (sleeve or cylinder) are the charges of the same name with the charged body.

Since the distance to the positive and negative charges in the cylinder from the ball is different, the forces of attraction prevail and the cylinder deviates towards the electrified body. If the far side of the body from the charged ball is touched by the hand, then the body will jump to the charged ball. This is due to the fact that in this case the electrons jump to the hand, thereby reducing the repulsive forces. Rice. D.

Teacher: How long will this situation last? (Fig.D)

Student: After a few seconds, the charges will divide and the cylinder will come off the ball. Their character in the future will depend on the value of the sum of their charges. If their sum is zero, then their interaction forces are zero. If Fp< 0, то они оттолкнутся друг от друга, но на меньший угол .

Teacher: Consider the electrification of bodies under the action of light energy (photoelectric effect).

Student: Let's direct a strong light beam to the zinc disk (plate) attached to the electrometer. Under the action of light energy, a certain number of electrons fly out of the plate. The plate itself is positively charged. The magnitude of this charge can be judged by the angle of deflection of the electrometer needle. (Fig. E)

Teacher: We have seen that with a decrease in the distance between atoms, the phenomenon of electrification occurs more efficiently. Why?

Student: Because this increases the Coulomb forces of attraction between the nucleus of an atom and the electron of a neighboring atom.

The electron that jumps is the one that is weakly bound to its nucleus.

Teacher: Consider how the chemical elements are arranged in the periodic table of chemical elements.

Student: There are about 500 forms of the Periodic Table of Chemical Elements. Of these, in one, 18-cell, the elements are arranged according to the structure of the electron shells of their atoms and is given in the reference book on general and inorganic chemistry by N.F. Stas.

The properties and characteristics of atoms, including the electronegativity and valence of elements, are consistent with the periodic law.

The radii of atoms and ions decrease in periods, because the electron shell of an atom or ion of each subsequent element in the period compared to the previous one becomes denser due to an increase in the charge of the nucleus and an increase in the attraction of electrons to the nucleus.

The radii in the groups increase because an atom (ion) of each element differs from the parent by the appearance of a new electronic layer. When an atom transforms into a cation (positive ion), the atomic radii decrease sharply, and when an atom transforms into an anion (negative ion), the atomic radii hardly change.

The energy expended on detaching an electron from an atom and turning it into a positive ion is called ionization. The voltage at which ionization occurs is called the ionization potential.

Ionization potential - a physical characteristic, is an indicator of the metallic properties of an element: the smaller it is, the easier it is for an electron to detach from an atom and the more pronounced are the metallic (reduction) properties of the element.

Table 1. Ionization potentials of atoms (eV/atom) of elements of the second period

Teacher: There is such a thing as electronegativity, which plays a decisive role in the electrification of bodies. The sign of the charge received by the element during electrification depends on it. Electronegativity - what is it?

Student: Electronegativity is the property of a chemical element to attract electrons from atoms of other elements to its atom, with which the element forms a chemical bond in compounds.

The electronegativity of elements was determined by many scientists: Pauling, Olred and Rochov. They came to the conclusion that the electronegativity of elements increases in periods, and decreases in groups, similar to ionization potentials. The lower the value of the ionization potential, the greater the probability of losing an electron and turning into a positive ion or a positively charged body, if the body is homogeneous.

Table 2. Relative electronegativity (ER) of the elements of the first, second and third periods.

Teacher: From all this we can draw the following conclusion: if two homogeneous elements from the same period interact, then we can say in advance which of them will be positively charged and which negatively.

A substance whose atom has a higher valence (greater than the group number) in relation to the atom of another substance will be negatively charged, and the second substance will be positive.

If homogeneous substances from the same group interact, then the substance with a lower period or series number will be negatively charged, and the second interacting body will be positively charged.

Teacher: In this lesson, we tried to reveal the mechanism of electrization of bodies. We found out for what reason the body after electrification receives a charge of one sign or another, i.e. answered the main question - why? (how, for example, the section of mechanics “Dynamics” answers the question: why?)

Now we list the positive and negative values ​​​​of the electrification of bodies.

Student: Static electricity can have a negative effect:

The attraction of hair to the comb;

Repulsion of hair from each other, like a charged plume;

Sticking to clothes of various small objects;

In weaving mills, sticking of threads to bobbins, which leads to frequent breaks.

The accumulated charges can cause electrical discharges, which can have various consequences:

Lightning (leads to fires);

A discharge in a fuel truck will cause an explosion;

When refueling with a combustible mixture, any discharge can lead to an explosion.

To remove static electricity, ground all devices and equipment, and even a fuel truck. Use a special antistatic agent.

Student: Static electricity can benefit:

When painting small parts with a paint sprayer, the paint and the body are charged with opposite charges, which leads to great paint savings;

For medicinal purposes, a static shower is used;

Electrostatic filters are used to clean the air from dust, soot, acid and alkaline fumes;

For smoking fish in special electrometers (fish is charged positively, and the electrodes are negatively charged, smoking in an electric field is ten times faster).

Summing up the lesson.

Teacher: Let's remember the purpose of our lesson and draw a brief conclusion.

• What was new in the lesson?
• What was interesting?
• What was important in the lesson?

Students' conclusions:

1. Phenomena in which bodies acquire the properties to attract other bodies are called electrification.
2. Electrification can occur by contact, through influence, when irradiated with light.
3. Substances are either electronegative or electropositive.
4. Knowing the belonging of substances, it is possible to predict what charges the interacting bodies will receive.
5. Friction only increases the area of ​​contact.
6. Substances are conductors and non-conductors of electricity.
7. Insulators accumulate charges where they are formed (at the points of contact).
8. In conductors, charges are distributed evenly throughout the volume.

Discussing and grading the participants of the lesson.

Literature.

1. G.S. Landsberg. Elementary textbook of physics. T.2. - M., 1973.
2. N.F. Stas. Handbook of General and Inorganic Chemistry.
3. I.G. Kirillova. Book for reading in physics. M., 1986.

electrification of tel.

2. Electrification of bodies.

These phenomena were discovered in ancient times. Ancient Greek scientists noticed that amber (the petrified resin of coniferous trees that grew on Earth many hundreds of thousands of years ago), when rubbed with wool, begins to attract various bodies to itself. In Greek, amber is an electron, hence the name "electricity".

A body which, after being rubbed, attracts other bodies to itself, is said to be electrified, or that an electric charge has been imparted to it.

Bodies made of different substances can be electrified. It is easy to electrify sticks made of rubber, sulfur, ebonite, plastic, nylon by rubbing wool on wool.

The electrification of bodies occurs when the bodies come into contact and then separate. Rubbing bodies against each other only to increase the area of ​​their contact.

Two bodies are always involved in electrification: in the experiments discussed above, a glass rod came into contact with a sheet of paper, a piece of amber - with fur or wool, a plexiglass rod - with silk. In this case, both bodies are electrified. For example, when a glass rod and a piece of rubber come into contact, both glass and rubber are electrified. Rubber, like glass, begins to attract light bodies.

Electric charge can be transferred from one body to another. To do this, you need to touch another body with an electrified body, and then part of the electric charge will pass to it. To make sure that the second body is also electrified, you need to bring small pieces of paper to it and see if they will be attracted.

3. Two kinds of charges. Interaction of charged bodies.

All electrified bodies attract other bodies, such as pieces of paper, to themselves. According to the attraction of bodies, it is impossible to distinguish the electric charge of a glass rod rubbed on silk from the charge received on an ebonite rod rubbed against them. After all, both electrified sticks attract pieces of paper.

Does this mean that the charges obtained on bodies made of different substances do not differ from each other in any way?

Let's turn to experiments. We electrify an ebonite stick suspended on a thread. Let's bring another similar stick to it, electrified by friction on the same piece of fur. The sticks repel Since the sticks are the same and electrified them by rubbing against the same body, we can say that they had charges of the same kind. This means that bodies having charges of the same kind repel each other.

Now let's bring a glass rod rubbed on silk to an electrified ebonite rod. We will see that the glass and ebonite rods are mutually attracted (Fig. No. 2). Consequently, the charge obtained on glass rubbed on silk is of a different kind than on ebonite rubbed on fur. So, there is another kind of electric charges.

We wake up to bring electrified bodies from various substances to a suspended electrified ebonite stick: rubber, plexiglass, plastic, nylon. We will see that in some cases the ebonite stick is repelled from the bodies brought to it, and in others it is attracted. If the ebonite stick is repelled, then the body brought to it has a charge of the same kind as on it. And the charge of those bodies, to which the ebonite stick was attracted, is similar to the charge obtained on glass rubbed on silk. Therefore, we can assume that there are only two kinds of electric charges.

The charge obtained on glass rubbed against silk (and on all bodies where a charge of the same kind is obtained) was called positive, and the charge obtained on amber (as well as ebonite, sulfur, rubber) rubbed against wool was called negative, i.e. The charges were assigned the signs “+” and “-”.

And so, experiments have shown that there are two kinds of electric charges - positive and negative charges, and that electrified bodies interact with each other in different ways.

Bodies with electric charges of the same sign repel each other, and bodies with charges of the opposite sign attract each other.

4. Electroscope. Conductors and non-conductors of electricity.

If the bodies are electrified, then they are attracted to each other or repel each other. By attraction or repulsion, one can judge whether an electric charge is imparted to the body. Therefore, the design of the device, with the help of which it is found out whether the body is electrified, is based on the interaction of charged bodies. This device is called an electroscope (from the Greek words electron and scopeo - to observe, to detect).

In the electroscope, a metal rod is passed through a plastic stopper (Fig. No. 3) inserted into a metal frame, at the end of which two sheets of thin paper are fixed. The frame is covered with glass on both sides.

The greater the charge of the electroscope, the greater the repulsive force of the leaves and the greater the angle they will disperse. This means that by changing the angle of the divergence of the leaves of the electroscope, one can judge whether its charge has increased or decreased.

If you touch a charged body (for example, an electroscope) with your hand, it will be discharged. Electric charges will pass to our body and through it they can go to the ground. A charged body will also be discharged if it is connected to the ground with a metal object, such as iron or copper wire. But if a charged body is connected to the earth with a glass or ebonite rod, then the electric charges through them will not go into the earth. In this case, the charged body will not be discharged.

According to the ability to conduct electric charges, substances are conditionally divided into conductors and non-conductors of electricity.

All metals, soil, solutions of salts and acids in water are good conductors of electricity.

Non-conductors of electricity, or dielectrics, include porcelain, ebonite, glass, amber, rubber, silk, nylon, plastics, kerosene, air (gases).

Bodies made of dielectrics are called insulators (from the Greek word isolaro - to seclude).

5. Divisibility of electric charge. Electron.

Let's charge a metal ball attached to the rod of the electroscope (Fig. No. 4a). Let us connect this ball with a metal conductor A, holding it by the handle B, made of a dielectric, with another exactly the same, but uncharged ball, located on the second electroscope. Half of the charge will pass from the first ball to the second (Fig. No. 4b). This means that the initial charge is discharged into two equal parts.

Now let's separate the balls and touch the second ball with our hand. From this, he will lose charge - discharged. Let's attach it again to the first ball, on which half of the original charge remains. The remaining charge will again be divided into two equal parts, and the fourth part of the original charge will remain on the first ball.

In the same way, one eighth, one sixteenth of the charge, etc. can be obtained.

Thus, experience shows that the electric charge can have a different value. Electric charge is a physical quantity.

One pendant is taken as a unit of electric charge (denoted as 1 C). The unit is named after the French physicist C. Coulomb.

In the experiment shown in Figure 4, it is shown that the electric charge can be divided into parts.

Does charge division exist?

To answer this question, it was necessary to perform more complex and accurate experiments than those described above, since very soon the charge remaining on the ball of the electroscope becomes so small that it is not possible to detect it with the help of an electroscope.

To divide the charge into very small portions, it is necessary to transfer it not to balls, but to small grains of metal or liquid droplets. By measuring the charge obtained on such small bodies, it was found that it is possible to obtain charge portions that are billions of billions of times smaller than in the described experiment. However, in all experiments, it was not possible to separate the charge beyond a certain value.

This allowed us to assume that the electric charge has a divisibility limit, or, more precisely, that there are charged particles that have the smallest charge, which are no longer divisible.

To prove that there is a limit to the division of electric charge, and to establish what this limit is, scientists conducted special experiments. For example, the Soviet scientist A.F. Ioffe set up an experiment in which small dust particles of zinc, visible only under a microscope, were electrified. The charge of the dust particles was changed several times, and each time it was measured by how much the charge had changed. Experiments have shown that all changes in the charge of a grain of dust were an integer number of times (i.e., 2, 3, 4, 5, etc.) greater than some definite smallest charge, i.e., the charge of a grain of dust changed, albeit very small, but whole portions. Since the charge from a grain of dust leaves with a particle of matter, Ioffe concluded that in nature there is such a particle of matter that has the smallest charge, which is no longer divisible.

This particle is called an electron.

The value of the electron charge was first determined by the American scientist R. Milliken. In his experiments, similar to those of A. F. Ioffe, he used small drops of oil.

The electron charge is negative, it is equal to 1.610 C (0.000 000 000 000 000 000 16 C). Electric charge is one of the basic properties of an electron. This charge cannot be "removed" from an electron.

The mass of an electron is 9.110 kg, it is 3700 times less than the mass of a hydrogen molecule, the smallest of all molecules. A fly's wing has a mass about 510 times that of an electron.

6. Nuclear model of the structure of the atom

The study of the structure of the atom practically began in 1897-1898, after the nature of cathode rays as a stream of electrons was finally established and the magnitude of the charge and mass of the electron were determined. The fact that electrons are released by a wide variety of substances led to the conclusion that electrons are part of all atoms. But the atom as a whole is electrically neutral, therefore, it must also contain another component, positively charged, and its charge must balance the sum of the negative charges of the electrons.

This positively charged part of the atom was discovered in 1911 by Ernest Rutherford (1871-1937). Rutherford proposed the following scheme for the structure of the atom. At the center of the atom is a positively charged nucleus, around which electrons revolve in different orbits. The centrifugal force that arises during their rotation is balanced by the attraction between the nucleus and the electrons, as a result of which they remain at certain distances from the nucleus. The total negative charge of the electrons is numerically equal to the positive charge of the nucleus, so that the atom as a whole is electrically neutral. Since the mass of electrons is negligible, almost the entire mass of an atom is concentrated in its nucleus. On the contrary, the size of the nuclei is extremely small even in comparison with the size of the atoms themselves: the diameter of an atom is about 10 cm, and the diameter of the nucleus is about 10 - 10 cm. small, there is only an insignificant part of the entire space occupied by the atomic system (Fig. No. 5)

7. Composition of atomic nuclei

Thus, Rutherford's discoveries laid the foundation for the nuclear theory of the atom. Since the time of Rutherford, physicists have learned many more details about the structure of the atomic nucleus.

The lightest atom is the hydrogen atom (H). Since almost the entire mass of an atom is concentrated in the nucleus, it would be natural to assume that the nucleus of the hydrogen atom is an elementary particle of positive electricity, which was named proton from the Greek word “protos”, which means “first”. Thus, a proton has a mass almost equal to the mass of a hydrogen atom (exactly 1.00728 carbon units) and an electric charge equal to +1 (if we take the electron charge equal to -1.602 * 10 C as a unit of negative electricity). Atoms of other, heavier elements contain nuclei that have a greater charge and, obviously, a greater mass.

Measurements of the charge of the nuclei of atoms showed that the charge of the nucleus of an atom in the indicated conventional units is numerically equal to the atomic, or ordinal, number of the element. However, it was impossible to admit, since the latter, being charged with the same name, would inevitably repel each other and, consequently, such nuclei would turn out to be unstable. In addition, the mass of atomic nuclei turned out to be more than the total mass of protons, which determine the charge of the nuclei of atoms of the corresponding elements, twice or more.

Then it was assumed that the nuclei of atoms contain protons in a number exceeding the atomic number of the element, and the excess positive charge of the nucleus thus created is compensated by the electrons that make up the nucleus. These electrons must obviously hold mutually repelling protons in the nucleus. However, this assumption had to be rejected, since it was impossible to admit the coexistence of heavy (protons) and light (electrons) particles in a compact nucleus.

In 1932, J. Chadwick discovered an elementary particle that does not have an electric charge, in connection with which it was called a neutron (from the Latin word neuter, which means "neither one nor the other"). The neutron has a mass slightly greater than that of the proton (exactly 1.008665 carbon units). Following this discovery, D. D. Ivanenko, E. N. Gapon and V. Heisenberg, independently of each other, proposed a theory of the composition of atomic nuclei, which has become generally accepted.

According to this theory, the nuclei of atoms of all elements (with the exception of hydrogen) consist of protons and neutrons. The number of protons in the nucleus determines the value of its positive charge, and the total number of protons and neutrons determines the value of its mass. Nuclear particles - protons and neutrons - are united under the common name nucleons (from the Latin word nucleus, which means "nucleus"). Thus, the number of protons in the nucleus corresponds to the atomic number of the element, and the total number of nucleons, since the mass of the atom is mainly concentrated in the nucleus, corresponds to its mass number, i.e. its atomic mass A rounded to an integer. Then the number of neutrons in the nucleus N can be found from the difference between the mass number and the atomic number:

Thus, the proton-neutron theory made it possible to resolve the contradictions that arose earlier in the ideas about the composition of atomic nuclei and its connection with the serial number and atomic mass.

8. Isotopes

The proton-neutron theory made it possible to resolve another contradiction that arose during the formation of the theory of the atom. If we recognize that the nuclei of the atoms of elements consist of a certain number of nucleons, then the atomic masses of all elements must be expressed as integers. For many elements, this is true, and minor deviations from integers can be explained by insufficient measurement accuracy. However, for some elements, the values ​​of atomic masses deviated so much from integers that this can no longer be explained by measurement inaccuracy and other random reasons. For example, the atomic mass of chlorine (CL) is 35.45. It has been established that approximately three-quarters of the chlorine atoms that exist in nature have a mass of 35, and one quarter - 37. Thus, the elements that exist in nature consist of a mixture of atoms that have different masses, but, obviously, the same chemical properties, i.e., there are varieties of atoms of the same element with different and, moreover, integer masses. F. Aston managed to separate such mixtures into constituent parts, which were called isotopes (from the Greek words “isos” and “topos”, which means “same” and “place” (here it means that different isotopes of one element occupy one place in the periodic system). From the point of view of the proton-neutron theory, isotopes are varieties of elements whose atomic nuclei contain a different number of neutrons, but the same number of protons. The chemical nature of an element is determined by the number of protons in the atomic nucleus, which is equal to the number of electrons in the shell of the atom. A change in the number of neutrons (with the same number of protons) does not affect the chemical properties of the atom.

All this makes it possible to formulate the concept of a chemical element as a type of atoms characterized by a certain charge of the nucleus. Among the isotopes of various elements, those were found that contain the same total number of nucleons in the nucleus with a different number of protons, that is, the atoms of which have the same mass. Such isotopes were called isobars (from the Greek word "baros", which means "weight"). The different chemical nature of the isobars convincingly confirms that the nature of an element is not determined by the mass of its atom.

For various isotopes, the names and symbols of the elements themselves are used, indicating the mass number that follows the name of the element or is indicated as an index at the top left of the symbol, for example: chlorine - 35 or Cl.

Different isotopes differ from each other in stability. 26 elements have only one stable isotope - such elements are called monoisotopic, (they are characterized mainly by odd atomic numbers), and their atomic masses are approximately equal to whole numbers. 55 elements have several stable isotopes - they are called polyisotopic (a large number of isotopes is characteristic mainly of even-numbered elements). For the rest of the elements, only unstable, radioactive isotopes are known. These are all heavy elements, starting with element No. 84 (polonium), and from relatively light ones - No. 43 (technetium) and No. 61 (promethium). However, radioactive isotopes of some elements are relatively stable (characterized by a long half-life), and therefore these elements, such as thorium, uranium, are found in nature. In the majority, however, radioactive isotopes are obtained artificially, including numerous radioactive isotopes of stable elements.

9. Electronic shells of atoms. Bohr's theory.

According to Rutherford's theory, each electron revolves around the nucleus, and the force of attraction of the nucleus is balanced by the centrifugal force arising from the rotation of the electron. The rotation of an electron is quite analogous to its rapid oscillations and should cause the emission of electromagnetic waves. Therefore, it can be assumed that a rotating electron emits light of a certain wavelength, depending on the frequency of the electron's orbit. But, emitting light, the electron loses part of its energy, as a result of which the balance between it and the nucleus is disturbed. To restore equilibrium, the electron must gradually move closer to the nucleus, and the frequency of the electron's revolution and the nature of the light emitted by it will also gradually change. In the end, having exhausted all the energy, the electron must "fall" on the nucleus, and the emission of light will stop. If in fact there was such a continuous change in the motion of an electron, its "fall" on the nucleus would mean the destruction of the atom and the cessation of its existence.

Thus, Rutherford's illustrative and simple nuclear model of the atom clearly contradicted classical electrodynamics. The system of electrons rotating around the nucleus cannot be stable, since the electron must continuously radiate energy during such rotation, which, in turn, must lead to its fall onto the nucleus and to the destruction of the atom. Meanwhile, atoms are stable systems.

These significant contradictions were partially resolved by the outstanding Danish physicist Niels Bohr (1885 - 1962), who developed in 1913 the theory of the hydrogen atom, which he based on special postulates, linking them, on the one hand, with the laws of classical mechanics and, on the other hand, with the quantum theory of energy radiation by the German physicist Max Planck (1858 - 1947).

The essence of quantum theory comes down to the fact that energy is emitted and absorbed not continuously, as was previously accepted, but in separate small but well-defined portions - energy quanta. The energy reserve of the radiating body changes in jumps, quantum by quantum; a fractional number of quanta the body can neither emit nor absorb.

The magnitude of the energy quantum depends on the frequency of the radiation: the higher the frequency of the radiation, the greater the magnitude of the quantum. Denoting the energy quantum through E, we write the Planck equation:

where h is a constant value, the so-called Planck constant, equal to 6.626 * 10 J * s., and is the frequency of the Debroil wave.

Radiant energy quanta are also called photons. By applying quantum concepts to the rotation of electrons around the nucleus, Bohr based his theory on very bold assumptions, or postulates. Although these postulates contradict the laws of classical electrodynamics, they find their justification in the amazing results they lead to, and in the complete agreement that is found between theoretical results and a huge number of experimental facts. Bohr's postulates are as follows:

An electron can move around not in any orbits, but only in those that satisfy certain conditions arising from quantum theory. These orbits are called stable, stationary or quantum orbits. When an electron moves along one of the stable orbits possible for it, it does not radiate electromagnetic energy. The transition of an electron from a distant orbit to a closer one is accompanied by a loss of energy. The energy lost by an atom during each transition is converted into one quantum of radiant energy. The frequency of the light emitted in this case is determined by the radii of the two orbits between which the transition of the electron takes place. Denoting the energy reserve of an atom at the position of an electron in an orbit more distant from the nucleus through En, and in a closer orbit through Ek, and dividing the energy lost by the atom En - Ek by Planck's constant, we obtain the required frequency:

= (En - Ek) / h

The greater the distance from the orbit in which the electron is located to the one to which it passes, the greater the frequency of the radiation. The simplest of the atoms is the hydrogen atom, around the nucleus of which only one electron revolves. Based on the above postulates, Bohr calculated the radii of possible orbits for this electron and found that they are related as the squares of natural numbers: 1: 2: 3: ...: n. The value of n is called the main quantum number.

Subsequently, Bohr's theory was extended to the atomic structure of other elements, although this was associated with some difficulties due to its novelty. It made it possible to resolve the very important question of the arrangement of electrons in the atoms of various elements and to establish the dependence of the properties of elements on the structure of the electron shells of their atoms. At present, schemes of the structure of atoms of all chemical elements have been developed. However, it must be borne in mind that all these schemes are only a more or less reliable hypothesis that makes it possible to explain many of the physical and chemical properties of elements.

As mentioned earlier, the number of electrons revolving around the nucleus of an atom corresponds to the ordinal number of the element in the periodic system. The electrons are arranged in layers, i.e. each layer has a certain filling or, as it were, saturating number of electrons. The electrons of the same layer are characterized by almost the same amount of energy, i.e. are about the same energy level. The entire shell of an atom breaks up into several energy levels. The electrons of each next layer are at a higher energy level than the electrons of the previous layer. The largest number of electrons N that can be at a given energy level is equal to twice the square of the layer number:

where n is the layer number. Thus, by 1-2, by 2-8, by 3-18, etc. In addition, it was found that the number of electrons in the outer layer for all elements, except for palladium, does not exceed eight, and in the penultimate layer - eighteen.

The electrons of the outer layer, as the most distant from the nucleus and, therefore, the least firmly connected with the nucleus, can break away from the atom and join other atoms, entering into the composition of the outer layer of the latter. Atoms that have lost one or more electrons become positively charged, since the charge of the atom's nucleus exceeds the sum of the charges of the remaining electrons. Conversely, atoms that have attached electrons become negatively charged. Charged particles formed in this way, qualitatively different from the corresponding atoms, are called ions. Many ions, in turn, can lose or gain electrons, while turning either into electrically neutral atoms or into new ions with a different charge.

10. Nuclear forces.

The hypothesis that atomic nuclei consist of protons and neutrons was confirmed by many experimental facts. This testified to the validity of the neutron-tonne model of the structure of the nucleus.

But the question arose: why do nuclei not decay into individual nucleons under the action of electrostatic repulsion forces between positively charged protons?

Calculations show that nucleons cannot be held together due to attractive forces of a gravitational or magnetic nature, since these forces are much less than electrostatic ones.

In search of an answer to the question of the stability of atomic nuclei, scientists suggested that some special forces of attraction act between all nucleons in the nuclei, which significantly exceed the electrostatic repulsive forces between protons. These forces were called nuclear.

The hypothesis of the existence of nuclear forces turned out to be correct. It also turned out that nuclear forces are short-range: at a distance of 10-15 m they are approximately 100 times greater than the forces of electrostatic interaction, but already at a distance of 10-14 m they turn out to be negligible. In other words, nuclear forces act at distances comparable to the size of the nuclei themselves.

11.Fission of uranium nuclei.

The fission of uranium nuclei by bombarding them with neutrons was discovered in 1939 by the German scientists Otto Gunn and Fritz Strassmann.

Let's consider the mechanism of this phenomenon. On (Fig. No. 7, a) the nucleus of the uranium atom (23592U) is conditionally depicted. Having absorbed an extra neutron, the nucleus is excited and deformed, acquiring an elongated shape (Figure 7, b).

We already know that two types of forces act in the nucleus: electrostatic repulsive forces between protons, which tend to break the nucleus, and nuclear attractive forces between all nucleons, due to which the nucleus does not decay. But nuclear forces are short-range, therefore, in an elongated nucleus, they can no longer hold parts of the nucleus that are very distant from each other. Under the action of electrostatic repulsive forces, the nucleus is torn into two parts (Fig. No. 7, c), which scatter in different directions with great speed and emit 2-3 neutrons.

It turns out that part of the internal energy of the nucleus is converted into the kinetic energy of flying fragments and particles. The fragments quickly slow down in the environment, as a result of which their kinetic energy is converted into the internal energy of the medium (i.e., into the interaction energy of the thermal motion of its constituent particles).

With the simultaneous fission of a large number of uranium nuclei, the internal energy of the medium surrounding uranium and, accordingly, its temperature increase noticeably (i.e., the medium heats up).

Thus, the reaction of fission of uranium nuclei goes with the release of energy into the environment.

The energy contained in the nuclei of atoms is colossal. For example, with the complete fission of all the nuclei present in 1 gram of uranium, the same amount of energy would be released as is released during the combustion of 2.5 tons of oil.

12. Nuclear power plants.

nuclear power plant (NPP) - a power plant in which atomic (nuclear) energy is converted into electrical energy. The power generator at a nuclear power plant is a nuclear reactor. The heat that is released in the reactor as a result of a chain reaction of nuclear fission of some heavy elements, then, just like in conventional thermal power plants (TPPs), is converted into electricity. Unlike thermal power plants operating on organic fuel, nuclear power plants run on nuclear fuel ( based on 233U, 235U, 239Pu) Fission of 1 g of uranium or plutonium isotopes releases 22,500 kWh, which is equivalent to the energy contained in 2,800 kg of reference fuel. The world's first nuclear power plant for pilot industrial purposes with a capacity of 5 MW was launched in the USSR on June 27, 1954 in the city of Obninsk. Prior to this, the energy of the atomic nucleus was used for military purposes. The launch of the first nuclear power plant marked the opening of a new direction in energy, which was recognized at the 1st International Scientific and Technical Conference on the Peaceful Uses of Atomic Energy (August 1955, Geneva).

Schematic diagram of a nuclear power plant with a water-cooled nuclear reactor (Fig. No. 6.). Heat released in the reactor core is taken in as a coolant by water (coolant) of the 1st circuit, which is pumped through the reactor by a circulation pump g Heated water from the reactor entering the heat exchanger (steam generator) 3, where it transfers the heat received in the reactor to the water of the 2nd circuit . The water of the 2nd circuit evaporates in the steam generator, and the steam is formed and enters the turbine 4.

Most often, 4 types of thermal neutron reactors are used at nuclear power plants: 1) water-cooled reactors with ordinary water as a moderator and coolant; 2) graphite-water with water coolant and graphite moderator; 3) heavy water with a water coolant and heavy water as a moderator 4) graphite-gas with a gas coolant and a graphite moderator.

Depending on the type and state of aggregation of the coolant, one or another thermodynamic cycle of NPP is created. The choice of the upper temperature limit of the thermodynamic cycle is determined by the maximum allowable temperature of fuel element claddings (TVEL) containing nuclear fuel, the allowable temperature of the nuclear fuel itself, as well as the properties of the coolant adopted for this type of reactor. At the nuclear power plant. a water-cooled thermal reactor usually uses low-temperature steam cycles. Gas-cooled reactors allow the use of relatively more economical steam cycles with increased initial pressure and temperature. The thermal scheme of the NPP in these two cases is performed as a 2-circuit one: the coolant circulates in the 1st circuit, the 2nd circuit is steam-water. In reactors with boiling water or high-temperature gas coolant, a single-loop thermal NPP is possible. In boiling water reactors, water boils in the core, the resulting steam-water mixture is separated, and saturated steam is sent either directly to the turbine, or previously returned to the core for overheating.

In high-temperature graphite-gas reactors, it is possible to use a conventional gas turbine cycle. The reactor in this case acts as a combustion chamber.

During operation of the reactor, the concentration of fissile isotopes in nuclear fuel gradually decreases, and the fuel burns out. Therefore, over time, they are replaced with fresh ones. Nuclear fuel is reloaded using remote-controlled mechanisms and devices. The spent fuel is transferred to the spent fuel pool and then sent for reprocessing.

The reactor and its service systems include: the reactor itself with biological protection, heat exchangers, pumps or blower units that circulate the coolant; pipelines and fittings of the circuit circulation; devices for reloading nuclear fuel; special systems ventilation, emergency cooling, etc.

Depending on the design, the reactors have the following features: in pressurized reactors, the fuel and moderator are located inside the vessel, which carries the total pressure of the coolant; in channel reactors, fuel cooled by a coolant is installed in special pipes-channels penetrating the moderator enclosed in a thin-walled casing. To protect NPP personnel from radiation exposure, the reactor is surrounded by biological protection, the main material for which are concrete, water, serpentine sand. The reactor circuit equipment must be completely sealed. A system is provided for monitoring places of possible leakage of the coolant, measures are taken so that the appearance of leaks and breaks in the circuit does not lead to radioactive emissions and pollution of the NPP premises and the surrounding area. The reactor circuit equipment is usually installed in sealed boxes, which are separated from the rest of the NPP premises by biological protection and are not serviced during reactor operation. ventilation system, in which, to exclude the possibility of atmospheric pollution, cleaning filters and holding gas holders are provided. The dosimetric control service monitors the compliance with the radiation safety rules by the NPP personnel.

In case of accidents in the reactor cooling system, in order to prevent overheating and leakage of fuel rod claddings, a rapid (within a few seconds) suppression of the nuclear reaction is provided; The emergency cooling system has independent power sources.

The presence of biological protection systems special. ventilation and emergency cooling and dosimetric control service allows you to completely protect the NPP maintenance personnel from the harmful effects of radioactive exposure.

The equipment of the NPP machine room is similar to the equipment of the TPP machine room. Distinguish, a feature of most nuclear power plants is the use of steam of relatively low parameters, saturated or slightly superheated.

At the same time, in order to exclude erosion damage to the blades of the last stages of the turbine by particles of moisture contained in the steam, separators are installed in the turbine. Sometimes it is necessary to use remote separators and reheaters of steam. Due to the fact that the coolant and the impurities contained in it are activated when passing through the reactor core, the design solution of the turbine hall equipment and the cooling system of the turbine condenser of single-loop NPPs should completely exclude the possibility of coolant leakage. At double-circuit NPPs with high steam parameters, such requirements are not imposed on the equipment of the turbine hall.

Part of the thermal power of the reactor of this nuclear power plant is spent on heat supply. In addition to generating electricity, nuclear power plants are also used to desalinate seawater. Nuclear power plants, which are the most modern type of power plants, have a number of significant advantages over other types of power plants: under normal operating conditions, they absolutely do not pollute the environment, do not require binding to a source of raw materials and, accordingly, can be placed almost anywhere, new power units have a capacity almost equal to that of an average hydroelectric power station , however, the installed capacity utilization factor at NPPs (80%) significantly exceeds that of HPPs or TPPs. The fact that 1 kg of uranium can produce the same amount of heat as when burning about 3000 tons of coal can speak about the efficiency and effectiveness of nuclear power plants.

There are practically no significant drawbacks of nuclear power plants under normal operating conditions. However, one cannot fail to notice the danger of nuclear power plants under possible force majeure circumstances: earthquakes, hurricanes, etc. - here old models of power units pose a potential danger of radiation contamination of territories due to uncontrolled overheating of the reactor.

13. Conclusion

Having studied in detail the phenomenon of electrification and the structure of the atom, I learned that the atom consists of a nucleus and negatively charged electrons around it. The nucleus is made up of positively charged protons and uncharged neutrons. When a body is electrified, either an excess or a shortage of electrons occurs on the electrified body. This determines the charge of the body. There are only two kinds of electric charges - positive and negative charges. As a result of my work, I became deeply acquainted with the phenomena of electrostatics and figured out how and why these phenomena occur. For example, lightning. The phenomenon of electrostatics is closely related to the structure of the atom. Atoms of substances such as uranium, radium, etc. possess radioactivity. The energy of the atom is of great importance for the life of all mankind. For example, the energy contained in one gram of uranium is equal to the energy released during the combustion of 2.5 tons of oil. At present, the radioactive energy of atoms has found its application in many areas of life. Every year more and more nuclear power plants (nuclear power plants) are being built, the production of icebreakers and submarines with a nuclear reactor is developing. Atomic energy is used in medicine for the treatment of various diseases, as well as in many areas of the national economy. Improper use of energy can pose a health hazard to living organisms. The energy of atoms can benefit people if they learn how to use it correctly.

Electrification body macroscopic body, usually electrically... task. 1 version. At electrification tel close contact between them is important ... should lead to charging body. Another way electrification tel- Impact on...

The culture of interaction is the interaction of cultures.

Interactive presentation of the topicElectrification of tel. Electric charge

Have you had fun with such a simple trick: if you rub an inflated balloon on dry hair, and then attach it to the ceiling, does it seem to “stick”?

Not? Try it! No less funny then the hair sticks out in all directions. The same effect is sometimes obtained when combing long hair. They stick out and stick to the comb. Well, everyone is familiar with situations when, walking in woolen or synthetic things, you touch something or someone and feel a sharp prick. In such cases, they say - shock. All these are examples of the electrification of bodies. But where does electrification come from, if we all know perfectly well that electric current lives in sockets and batteries, and not in hair and clothes? Watch the cartoon

The phenomenon of electrification of bodies: methods of electrization

Electrification of bodies upon contact (rubbing of an ebonite or glass rod against fur or silk). Rub the pen on wool or fur, and then bring it to finely chopped pieces of paper, straws or wool. You will see how these pieces are attracted to the handle. The same will happen with a thin stream of water if you bring an electrified handle to it.

Two kinds of electric charges

First similar effects have been found with amber, therefore they were called electric from the Greek word "electron" - amber.Amber. Time: 5:32 And the ability of bodies to attract other objects after contact, and rubbing is just a way to increase the area of ​​\u200b\u200bcontact, was called electrification or giving the body an electric charge. It has been experimentally established that There are two kinds of electric charges. If you rub glass and ebonite rods, they will be attracted to each other. And two the same - repel. And this is not because they do not like each other, but because they have different electrical charges. It was agreed to call the electric charge of a glass rod positive, and that of an ebonite rod negative. They are designated, respectively, by the signs "+" and "-". It means that they are opposite to each other.

Nowadays, easily electrified objects are widely used - plastics, synthetic fibers, petroleum products. When such substances are rubbed, an electric charge arises, which is sometimes at least unpleasant, at most it can be harmful. In industry, they are fought with special means. In everyday life the same easy way to get rid of electrification is to wet an electrified surface. If water is not at hand, touching metal or earth will help. These bodies will remove the electrification. And in order not to feel these unpleasant effects at all, it is recommended to use antistatic agents.

Ticket 7. Electrification of tel. Experiments illustrating the phenomenon of electrification. Two kinds of electric charges. Interaction of charges. Electric field. Explanation of electrical phenomena. Conductors and non-conductors of electricity.

An electrified body acquires the property of attracting small objects to itself. For example, if you rub a glass rod on a sheet of paper, and then bring it to finely chopped pieces of paper, they will begin to attract.

A body that has this property is said to be electrified or what is communicated to him electric charge.

Electrification This is the phenomenon of the acquisition of a charge by the body.

Charges are positive and negative. Like charges repel, unlike charges attract.

The concept of positive and negative charges was introduced in 1747 by Franklin. An ebonite stick from electrification on wool and fur is negatively charged. The charge formed on a glass rod rubbed with silk was called positive by Franklin.

Charge is a physical quantity, measure of the properties of charged bodies to interact with each other..
q - charge
[q]=Cl

Types of electrification:

1) electrification by friction: dissimilar bodies are involved. The bodies acquire the same modulus, but different in sign charges.

2) electrification by contact: when a charged and uncharged body comes into contact, part of the charge passes to an uncharged body, that is, both bodies acquire the same charge in sign.

3) electrification through influence: when electrifying through influence, you can get a negative charge on the body using a positive charge, and vice versa.

A device for measuring the amount of charge is an electrometer. A device for determining the presence of a charge is an electroscope.

The interaction of electric charges was studied by English physicists Michael Faraday and James Maxwell. If you place a charged electroscope under the bell of an air pump, the leaves of the electroscope still repel each other. (The air has been evacuated from under the bell.) As a result, it has been established that any charged body is surrounded by an electric field.

Electric field is a special kind of matter, different from matter. An electric field is a special kind of matter that exists around charged bodies and reveals itself by interaction with other charged bodies.

Our sense organs do not perceive an electric field. The field can be detected due to the fact that it acts on every charge in it. This explains the interaction of electrified bodies.

The force with which an electric field acts on an electric charge introduced into it is called electrical force. The electric field surrounding one of the charges acts with some force on another charge placed in the field of the first charge. Conversely, the electric field of the second charge acts on the first.

conductors are bodies capable of conducting electrical charges. These include all metals, liquids (solutions of salts and alkalis).

Dielectrics are substances that do not conduct electrical charges. These include: distilled water, plastic, rubber, wood, glass, paper, concrete, stones, etc.

1) When electrifying bodies, the law of conservation of electric charge is fulfilled. The algebraic sum of electric charges remains constant for any interactions in a closed system, i.e. q1 + q2 + q3 + ... + qp \u003d const, a system is considered closed if electric charges do not enter or exit from the outside. If a neutral body acquires electrons from some other body, then it will receive a negative charge. Thus, a body is negatively charged if it has an excess, in comparison with the normal, number of electrons. And if a neutral body loses electrons, then it receives a positive charge. Therefore, a body has a positive charge if it does not have enough electrons.

2) explanation of electrization by friction: during friction, electrons from one body pass to another. Where there are more electrons, the body is charged negatively, where there are fewer - positively.

3) In atoms, electrons are at different distances from the nucleus, distant electrons are weaker attracted to the nucleus than nearby ones. The remote electrons are especially weakly retained by the nuclei of metals. Therefore, in metals, the electrons farthest from the nucleus leave their place and move freely between atoms. These electrons are called free electrons. Those substances in which there are free electrons are conductors.

4) There are free electrons in the sleeve. As soon as the sleeve is introduced into the electric field, the electrons will move under the action of the field forces. If the stick is positively charged, then the electrons will go to the end of the sleeve, which is located closer to the stick. This end will be negatively charged. There will be a shortage of electrons at the opposite end of the sleeve, and this end will be positively charged. The negatively charged edge of the shell is closer to the stick, so the shell will be attracted to it. When the sleeve touches the stick, some of the electrons from it will go to the positively charged stick. There will be a positive charge on the sleeve).

5) If the charge is transferred from a charged ball to an uncharged one, and the sizes of the balls are the same, then the charge will be divided in half. But if the second, uncharged ball is larger than the first, then more than half of the charge will go to it. The larger the body to which the charge is transferred, the greater part of the charge will transfer to it. Grounding is based on this - the transfer of charge to the earth. The globe is large compared to the bodies on it. Therefore, when in contact with the earth, a charged body gives it almost all of its charge and practically becomes electrically neutral.

Under normal conditions, microscopic bodies are electrically neutral because the positively and negatively charged particles that form atoms are connected to each other by electrical forces and form neutral systems. If the electrical neutrality of the body is violated, then such a body is called electrified body. To electrify a body, it is necessary that an excess or deficiency of electrons or ions of the same sign be created on it.

Methods of electrification of bodies, which represent the interaction of charged bodies, can be as follows:

1. Electrification of bodies upon contact. In this case, with close contact, a small part of the electrons passes from one substance, in which the bond with the electron is relatively weak, to another substance.
2. Electrization of bodies during friction. This increases the contact area of ​​the bodies, which leads to increased electrification.
3. Influence. Influence is based phenomenon of electrostatic induction, that is, the induction of an electric charge in a substance placed in a constant electric field.
4. Electrification of bodies under the action of light. This is based on photoelectric effect, or photoelectric effect when, under the action of light, electrons can fly out of the conductor into the surrounding space, as a result of which the conductor is charged.

negative charge body is due to an excess of electrons on the body compared to protons, and positive charge due to a lack of electrons.

When the electrification of the body occurs, that is, when the negative charge is partially separated from the positive charge associated with it, law of conservation of electric charge. The law of conservation of charge is valid for a closed system, which does not enter from the outside and from which charged particles do not go out. The law of conservation of electric charge is formulated as follows:

In a closed system, the algebraic sum of the charges of all particles remains unchanged:

q 1 + q 2 + q 3 + ... + q n = const

Where q 1 , q 2 etc. are the particle charges.

Interaction of electrically charged bodies

Interaction of bodies, having charges of the same or different signs, can be demonstrated in the following experiments. We electrify the ebonite stick by rubbing against the fur and touch it to a metal sleeve suspended on a silk thread. Charges of the same sign (negative charges) are distributed on the sleeve and ebonite stick. Approaching a negatively charged ebonite rod to a charged cartridge case, one can see that the cartridge case will be repelled from the stick (Fig. 1.2).

Rice. 1.2. Interaction of bodies with charges of the same sign.

If we now bring a glass rod rubbed on silk (positively charged) to the charged sleeve, then the sleeve will be attracted to it (Fig. 1.3).

Rice. 1.3. Interaction of bodies with charges of different signs.

It follows that bodies with charges of the same sign (like charged bodies) repel each other, and bodies with charges of different signs (oppositely charged bodies) attract each other. Similar inputs are obtained if two sultans are brought closer, similarly charged (Fig. 1.4) and oppositely charged (Fig. 1.5).