What are the two types of charges. I. S. Stekolnikov Lightning and Thunder. Improvement of electrostatic machines

"Electrization of bodies. Two types of electric charge" Nikonov Evgeny Gavrilyevich Physics Grade 8

Lesson objectives: educational: the formation of initial ideas about the electric charge, the interaction of charged bodies, the existence of two types of electric charges. elucidation of the essence of the process of electrification of bodies. determination of the sign of the charge of an electrified body. developing: development of skills to highlight electrical phenomena in nature and technology. familiarization with brief historical information on the study of electric charges. educational: education of the ability to work in a team, education of curiosity.

Equipment: an electroscope (electrometers), a foil sleeve on a stand, glass and ebonite rods, a piece of fur and lye, polyethylene, paper, a plastic comb (handle), a tripod, a burette with water, a cup for collecting water, a computer, a projector, an interactive whiteboard .

In ancient Greece, in the beautiful city of Miletus, the philosopher Thales lived. And then one evening his beloved daughter comes up to him. Explain why my threads get tangled when I work with an amber spindle, dust and straws stick to the yarn. It is very uncomfortable. Thales takes the spindle, rubs it and sees small sparks. Remember the Russian proverb: "Until the thunder breaks out, the peasant will not cross himself." And what is thunder without lightning? How many millions of times must lightning flash for a man, crossing himself, to finally think: what is it?

Between the rubbed amber spindle, which attracts objects, and lightning, it would seem that there is nothing in common. But all this is ELECTRICAL PHENOMENA Why do these phenomena occur? What is the essence of these phenomena? This is what we have to find out in today's and upcoming lessons.

Write down the topic of the lesson. Each of you, by the end of the lesson, should learn to explain: what is an electric charge and electrification, how charged bodies interact with each other, how the simplest electroscope device works, what charges exist in nature

Consider first the origin of the term "electricity" The history of the development of electricity begins with Thales of Miletus. Initially, the ability to attract small objects was attributed only to amber (petrified resin of coniferous trees). From the name of which the word electricity originated, i.e. to the Greek. elektron-amber. Only at the end of the 16th century and the beginning of the 17th century was this discovery remembered. The English physician and naturalist William Gilbert (1544 - 1603) found out that many substances can become electrified during friction. He was one of the first scientists who approved experience, experiment as the basis of research.

If a piece of amber is rubbed against wool or a glass rod - paper or silk, then you can hear a slight crackle, sparks in the dark, and the rod itself acquires the ability to attract small objects. water About the body, which, after rubbing, attracts other bodies to itself, they say that it is electrified or that it was given an electric charge.

By the attraction of bodies to each other, one can judge whether the bodies have an electric charge. There are devices with which you can judge the electrification of bodies - an electroscope (an electron - I observe)

Electrization can occur in several ways: 1. CONTACT Newton was also involved in electrical experiments, who observed the electrical dance of pieces of paper placed under glass placed on a metal ring. When rubbing the glass, the pieces of paper were attracted to it, then bounced off, attracted again, etc. Newton carried out these experiments back in 1675. electrification is made by friction: “They are rubbed with bodies that do not spoil their surface and bring shine, for example, hard silk, coarse non-staining cloth and a dry palm. Tinder is also amber on amber, on diamond, on glass and much more. This is how electrical bodies are processed.” Bodies rub against each other to increase the area of ​​their contact.

All electrified bodies attract other bodies, such as pieces of paper, to themselves. By attraction, it is impossible to distinguish the electric charge of a glass rod rubbed on silk from the charge received on an ebonite rod rubbed on fur. After all, both electrified sticks attract pieces of paper to themselves. But electrified bodies can also repel each other. (sleeve and stick). Why?

So, electric charge is a measure of the properties of charged bodies to interact with each other. What types of interaction do you know? Conventionally, the charges were called positive (worn on glass on silk) and negative (on amber, ebonite, sulfur, rubber worn on wool). Positive charge in physics is denoted by +q or q Negative charge - -q

+ + + - What will happen to these balls? - And how will these balls behave? Bodies with charges of the same sign repel each other, and bodies with charges of the opposite sign attract each other.

Conclusion: One of the types of electrification is the friction of bodies. In this case, there are always two bodies (or more) involved. Both bodies are electrified.

Electrification is also observed during the friction of liquids against metals during the flow, as well as splashing upon impact. For the first time, the electrification of a liquid during crushing was seen near waterfalls in Switzerland in 1786. Since 1913, the phenomenon has been called the balloelectric effect.

Primary control: Now we will complete a small test task, which you will check with each other and immediately put marks. You have five minutes to complete. Answers: 1st option A B A C B 2nd option B B A C B

QUALITATIVE TASKS 1. What precautions should be taken so that when gasoline is poured from one tank into another, it does not ignite? (During transportation and during transfusion, gasoline becomes electrified, a spark may occur and the gasoline will flare up. To prevent this from happening, both tanks and the pipeline connecting them are grounded). 2. A steel chain is attached to the fuel truck tank, the lower end of which touches the ground with several links. For what? Why is there no such chain on the railway tank car? (Because the railway tank is grounded through the rail wheels) 3. If you take one nylon stocking out of the other and hold each in your hand in the air, they expand. Why? (During friction, the stockings become electrified. Charges of the same name repel each other. Therefore, the surface of the stocking swells.)

Electricity, obtained by friction on a particular body, turns out to be unequal in its properties.

Let's do the following experiment. With the help of a silk thread, we hang a light cork or elderberry ball on the stand and then, having electrified the ebonite stick by rubbing against fur or cloth, we bring it to the cork ball. In this case, the following will happen: at first, the ball will quickly be attracted to the ebonite stick (Fig. 2), but as soon as it touches it, it will immediately repel and take up the position shown in Fig. 3. If a glass rod, electrified by friction against silk or leather, is brought to this charged ball, the ball will be attracted to it.

Rice. 2. The attraction of a cork ball to an electrified stick

Rice. 3. Repulsion of a cork ball that received a charge from an electrified stick

Let us now take two balls suspended from two stands on silk threads, and touch each of them with an electrified glass rod.

Approaching after this both balls one to another, we note that they will tend to repel and take the position shown in Fig. 4. The same thing will happen if both balls are charged with an electrified ebonite rod.

Rice. 4. Balls with like charges repel each other

Completely different properties will be discovered if the first of the two balls is charged by touching it with an electrified glass rod, and the other ball is electrified with an ebonite rod. The balls will be attracted to one another (Fig. 5).

Rice. 5. Balls with opposite charges attract

The experiments carried out show that it is necessary to distinguish between two electrical states of bodies, or, as they say, two kinds of electricity:

1) electricity produced on glass by rubbing it against silk cloth or skin, which was agreed to be called positive electricity;

2) electricity obtained on ebonite by rubbing it against fur or woolen matter, which was agreed to be called negative electricity.

Positive electricity is usually denoted by a plus sign (+), and negative electricity by a minus sign (-).

Bodies electrified by electricity of the same name, whether positive or negative, repel one another (Fig. 4). The bodies, electrified by opposite electricity, are attracted to one another (Fig. 5).

At the same time, it must be borne in mind that the attraction or repulsion of the electrified balls will be the stronger, the smaller the distance between them and the greater the charge imparted to each of the balls.

It should also be remembered that if, by rubbing a glass rod with silk, we receive positive electricity on the glass rod, then, in turn, we receive negative electricity in the same amount on silk. And, on the contrary, when ebonite is rubbed against fur on ebonite, we get negative electricity, and the fur itself is electrified positively.

Simple experiments on the electrification of various bodies illustrate the following points.

1. There are two types of charges: positive (+) and negative (-). A positive charge arises when glass is rubbed against leather or silk, and a negative charge occurs when amber (or ebonite) is rubbed against wool.

2. Charges (or charged bodies) interact with each other. Charges of the same name repel, and unlike charges are attracted.

3. The state of electrification can be transferred from one body to another, which is associated with the transfer of electric charge. In this case, a larger or smaller charge can be transferred to the body, i.e., the charge has a value. When electrified by friction, both bodies acquire a charge, one positive and the other negative. It should be emphasized that the absolute values ​​of the charges of bodies electrified by friction are equal, which is confirmed by numerous measurements of charges using electrometers.

It became possible to explain why bodies are electrified (i.e., charged) during friction after the discovery of the electron and the study of the structure of the atom. As you know, all substances are composed of atoms; atoms, in turn, consist of elementary particles - negatively charged electrons, positively charged protons and neutral particles - neutrons. Electrons and protons are carriers of elementary (minimal) electric charges.

elementary electric charge ( e) is the smallest electric charge, positive or negative, equal to the charge of an electron:

e = 1.6021892(46) 10 -19 C.

There are many charged elementary particles, and almost all of them have a charge. +e or -e, however, these particles are very short-lived. They live less than a millionth of a second. Only electrons and protons exist in a free state indefinitely.

Protons and neutrons (nucleons) make up the positively charged nucleus of an atom, around which negatively charged electrons revolve, the number of which is equal to the number of protons, so that the atom as a whole is a power plant.

Under normal conditions, bodies consisting of atoms (or molecules) are electrically neutral. However, in the process of friction, some of the electrons that have left their atoms can move from one body to another. In this case, the displacements of electrons do not exceed the sizes of interatomic distances. But if the bodies are separated after friction, then they will be charged; the body that has donated some of its electrons will be positively charged, and the body that has acquired them will be negatively charged.

So, bodies become electrified, that is, they receive an electric charge when they lose or gain electrons. In some cases, electrification is due to the movement of ions. New electric charges do not arise in this case. There is only a division of the available charges between the electrified bodies: part of the negative charges passes from one body to another.

Charge definition.

It should be emphasized that the charge is an inherent property of the particle. A particle without a charge can be imagined, but a charge without a particle cannot be imagined.

Charged particles manifest themselves in attraction (opposite charges) or in repulsion (charges of the same name) with forces that are many orders of magnitude greater than gravitational ones. Thus, the force of electric attraction of an electron to the nucleus in a hydrogen atom is 10 39 times greater than the force of gravitational attraction of these particles. The interaction between charged particles is called electromagnetic interaction, and the electric charge determines the intensity of electromagnetic interactions.

In modern physics, charge is defined as follows:

Electric charge- this is a physical quantity, which is the source of the electric field, through which the interaction of particles with a charge is carried out.

The purpose of the work: acquaintance with the history of the development of electrical engineering, with the creative path of the most prominent scientists who have contributed to the study of electrical and magnetic phenomena, identifying their patterns, creating electrical devices.

Shutdown

7. Discovery of the phenomenon

3. Development of electrostatics of electrostatic induction. The study of electrization processes

8. Interaction research

4. Invention of the Leyden jar of charged bodies. Discovery of Coulomb's Law

The first observations of magnetic and electrical phenomena date back to ancient times. The mysterious ability of a magnet to attract iron objects is mentioned in ancient chronicles and legends that have come down to us from Asia (India and China), Ancient Greece and Rome.

A very figurative explanation of the properties of a magnet is given in the famous poem "On the Nature of Things" by the Roman poet Lucretius (99-55 BC), written more than 2 thousand years ago.

From ancient legends and chronicles dating back to the second millennium BC, we learn about many interesting facts about the practical use of a magnet. The ancient Indians used a magnet to extract iron arrowheads from the bodies of wounded warriors. The Chinese chronicles tell of a magical magnetic gate through which a person who hid a metal weapon could not pass. During the excavations of the Olmec settlement (Central America), sculptures of three thousand years ago, carved from magnetic blocks, were found.

In China in the second millennium BC. the first compasses of various designs were already used. In one of the museums, a thousand-year-old Chinese compass resembling a spoon is kept.

Naturally, the ancient scientists and

naturalists pondered over the reason for the mysterious properties of the Chinese compass magnet. Plato, for example,

explained their divine origin.

First observations of magnetic and electrical phenomena

WITH named after one of the ancient sages - Thales(640-550 BC) legends that have come down to us are connected

O the property of rubbed amber to attract light bodies. In his opinion, in amber, as in a magnet, there is a soul, which is the root cause of attraction.

Amber products, shiny and beautiful, were widely used by ancient people for decoration, so it is likely that many could notice that rubbed amber attracts light straws, pieces of fabric, etc.

The Greeks called amber "electron". From this, many centuries later, the word "electricity" came about. It is known that one of the ancient Greek writings described a stone (apparently precious), which, like amber, was electrified by friction. But the ancient Greeks probably did not know about the electrification of other bodies.

And one more curious phenomenon did not go unnoticed by the ancient peoples who lived on the Mediterranean coast and in the basin of the river. Nile. We are talking about "electric" fish - stingray and catfish. The Greeks called them "narke", which means "paralyzing". In contact with these fish, which have electric organs, a person experienced strong blows. It is known that in the 1st century AD. Roman physicians used the electric ramp to treat gout, headaches, and other ailments.

And, of course, the ancient peoples observed menacing peals of thunder and bright flashes of lightning, which instilled in them a natural fear, but not one of the wise men of those times could have come up with the idea that the attraction of rubbed amber, and the blows of electric fish, and the phenomena of a thunderstorm in the atmosphere are of the same nature.

The decline of ancient culture was noticeably reflected in the study of electrical and magnetic phenomena. It follows from numerous sources that practically until 1600 not a single discovery was made in the field of electrical phenomena, and in the field of magnetism, only ways were described to use the compass by navigators (Arabs in the 9th, and Europeans in the 11th century).

In the XIII century. scientists managed to establish a number of properties of a magnet: the existence of opposite poles and their interaction; propagation of magnetic action through various bodies (paper, wood, etc.); methods for making magnetic arrows were described, and the French scientist Pierre Peregrine (1541-1616) first supplied the compass with a graduated scale.

In the XIII-XIV centuries. Catholic captains used the compass secretly, fearing to fall on the fire of the Inquisition, which saw in the compass a diabolical tool created by sorcerers.

For many centuries, magnetic phenomena were explained by the action of a special magnetic fluid, and as will be shown below, only the outstanding French physicist A.M. Ampere in the 20s of the XIX century. first explained the electrical nature of magnetism.

Experimental studies by W. Gilbert

A significant turning point in the ideas about electrical and magnetic phenomena occurred at the very beginning of the 17th century, when the fundamental scientific work of a prominent English scientist (doctor of the English Queen Elizabeth) was published. William Gilbert(1554--1603) "About the magnet, magnetic bodies and the large magnet - the Earth" (1600). As a follower of the experimental method in natural science, W. Hilbert conducted more than 600 skillful experiments, which, as he wrote, revealed the secrets of the "hidden causes of various phenomena."

Unlike many of his predecessors, W. Gilbert believed that the magnetic needle moves under the influence of the magnetism of the Earth, which is a large magnet. He based his conclusions on an original experiment that he had carried out for the first time. He made a small ball from magnetic iron ore - “a small Earth - terella” and proved that the magnetic needle takes the same positions with respect to the surface of this “terella” as it takes in the field of terrestrial magnetism. He established the possibility of magnetizing iron by means of terrestrial magnetism.

Investigating magnetism, W. Hilbert also took up the study of electrical phenomena. He proved that not only amber, but also many other bodies have electrical properties: diamond, sulfur, resin, rock crystal

Electrifying when rubbed. These bodies he called "electric" in accordance with the Greek name for amber (electron). But W. Hilbert unsuccessfully tried to electrify metals without isolating them, and therefore came to the erroneous conclusion that it was impossible to electrify metals by friction. This conclusion of W. Hilbert was convincingly refuted two centuries later by an outstanding Russian electrical engineer academician Vasily Vladimirovich Petrov.

W. Gilbert correctly established that the "degree of electrical force" is different, and moisture reduces the electrification of bodies when rubbed. Comparing magnetic and electrical phenomena, W. Gilbert argued that they are of a different nature: for example, "electric force" comes only from friction, while magnetic constantly acts on iron; a magnet lifts bodies of considerable gravity, electricity - only light bodies. This erroneous conclusion of W. Hilbert lasted in science for more than 200 years.

The idea that electrical phenomena are due to the presence of a special "electric fluid", similar to "heat-producing" and "light-creating" were characteristic of the science of that period when mechanical views on many natural phenomena were dominant.

Fundamental work B, Hilbert withstood during the XVII century. several editions, it was a reference book for many naturalists in different countries of Europe and played a huge role in the development of the theory of electricity and magnetism. The great G. Galileo wrote about the writings of W. Gilbert: "I give the greatest praise and envy this author."

Electrostatic machine O. Guericke

One of the first who, having become acquainted with the book of W. Hilbert, decided to get stronger manifestations of electrical forces, was the Magdeburg burgomaster Otto von Guericke (1602-1686).

In 1650, he made a ball of sulfur the size of a child's head, planted it on an iron axle mounted on a wooden tripod. With the help of a handle, the ball could rotate and was rubbed with the palms of the hands or with a piece of cloth pressed against the ball by hand. It was the first simple electrostatic machine.

O. Gerika managed to notice a faint glow of an electrified ball in the dark and, what is especially important, discovered for the first time that the fluffs attracted by the ball repel him after a while. This phenomenon is neither O. Guericke. nor many of his contemporaries could explain for a long time.

The German scientist G.W. Leibniz (1646-1716), using O. Guericke's machine, observed an electric spark - this is the first mention of this mysterious phenomenon.

Improvement of electrostatic machines

During the first half of the XVII century. the electrostatic machine has undergone a number of improvements: the sulfur ball was replaced by a glass one (since the glass was more intensely electrified), and later, instead of balls or cylinders (which were more difficult to manufacture, and they often exploded when heated), glass disks began to be used. For rubbing, leather pads were used, pressed against the glass with springs; later, to enhance the electrification, the pads were covered with amalgam.

An important new element in the design of the machine was the conductor (1744) - a metal tube suspended on silk threads, and later mounted on insulated supports. The conductor served as a reservoir for collecting electrical charges formed during friction. After the invention of the Leyden jar, it was also installed next to the machine.

electrostatic machine. End of the 18th century Unknown master.

Instrumental Chamber of the St. Petersburg Academy of Sciences

Two types of electricity are identified and the laws of their interaction are established. Conducting and insulating properties of materials are found.

Experiments on the transfer of electric charge. Discovery of electrical conductivity

A significant step in the study of the properties of electric charges was the research of a member of the English Royal Society Stephen Gray (1670-1736) and a member of the Paris Academy of Sciences Charles Francois Dufay(1698 -1736).

As a result of numerous experiments, S. Gray managed to establish that the electrical ability of a glass tube to attract light bodies can be transferred to other bodies, and he showed (1729) that bodies, depending on their relationship to electricity, can be divided into two groups: conductors ( e.g. metal thread, wire) and non-conductors (e.g. silk thread).

Continuing the experiments of S. Gray, Sh.F. Dufay (in 1733) discovered two kinds of electric charges - "glass" and "resin" and their peculiarity is to repel like charges and attract opposite charges.

Dufay also created a prototype of an electroscope in the form of two suspended and divergent when electrified

By the end of the 30s of the XVIII century. were successfully used as conductors: linen thread (Guericke, 1663), hemp twine, uncured wood, metal wire (Gray, 1729), wet catgut (Desaguliers,

1738); as non-conductors: silk (Wheeler in an experiment set by Gray, 1729), horsehair (Gray, 1729), glass and sealing wax (Dufay, 1733). The length of electrical lines reached several hundred meters.

O. Guericke, conducting experiments with an electrostatic machine, discovered that a sulfur ball rubbed with hands transfers its ability to attract light bodies to a cubit-long linen thread, the end of which, hooked to a stick, is located at the ball itself; attraction was observed within more than an inch from the lower end of the thread.

Using a glass tube (or stick), Stephen Gray repeated Guericke's experiment. In 1729, Gray discovered a number of bodies to which a tube could impart "electric force." These are wooden rods and wire (iron and brass) that Gray inserted into the tube (through the cork), hemp string, which he tied to the tube or pushed into it. The maximum length of indoor power transmission along a string or wire hanging from a tube did not exceed 1 m, and the maximum length of a horizontal room "power transmission" along docked wooden conductors was no more than 5.5 m, including the length of the tube. Gray checked the message of "electric force" to the bodies with the help of a fluff, which could be attracted to the body, repelled from it, hover

in the air.

Gray decided to try to transmit electricity horizontally in order to find out the question that occupied him, how far electricity could be transmitted. To do this, he hung a string on nails driven into a wooden beam at the same height. The experience didn't work. Gray correctly concluded that the electricity went into the beam.

The difficulty was overcome thanks to the brilliant idea of ​​Wheeler, with whom Gray experimented in the summer of 1729. The priest Granville Wheeler (d. 1770) proposed supporting the line of communication (according to Gray) with a silk cord, and not hanging it on nails driven into a beam . The first experience exceeded all expectations. Electricity was transmitted along a line about 25 m long. By replacing the silk cord with metal wire, Gray again got a negative result.

Gray "... showed that electricity can be transmitted without touching the transmission line with a tube, but only by holding the tube near the line", i.e., in later terminology, using electrostatic induction.

Summer afternoon. Soars. Suddenly, the sky begins to darken rapidly. It blows cool. A gust of wind picks up dust and carries it along the street. A few minutes pass, and the first large drops of rain fall to the ground, leaving large dark spots on the dust. Soon the rain intensifies - now it has already poured with strong jets, creating a continuous curtain of water. Suddenly, a winding fiery ribbon flashed in the leaden sky ... Lightning! She hit somewhere close, and after a second or two there was such a sound, as if gunshots rumbled nearby. A few more lightning bolts, strong peals of thunder - and the rain subsided, the sky cleared up. The storm swept past.

Powerful peals of thunder and blinding flashes of lightning used to inspire fear in people. Observing the destruction sometimes caused by lightning, a person full of prejudices and superstitions believed that gods or powerful forces cause lightning, that lightning “as punishment” kills and maims people and burns their shelter. In ancient Greek legends, it is said that the main Greek god - the Thunderer Zeus - in his anger throws fiery arrows - lightning. In Russian beliefs, it was believed that the storm was controlled by "Ilya the Prophet", driving in his chariot across the sky.

However, despite the fear of lightning, already in ancient times, people carefully observed and studied this formidable and beautiful natural phenomenon. Scientists have been studying it for several decades. Thanks to their selfless and hard work, one of the most interesting phenomena of nature - lightning and the thunder that accompanies it - has now received a complete scientific explanation. It turned out that there is nothing mysterious in this phenomenon and that “divine forces” have nothing to do with it. Scientists can artificially create lightning, albeit on a small scale, in their laboratories. Quite tiny lightning bolts can be obtained, as it is described further, by each reader of this book.

People sought to study lightning not just out of curiosity. They wanted to learn how to fight it, they wanted to defeat it. Undefeated lightning is very dangerous. It can fatally strike a person, destroy a building, cause explosions and fires that cause millions of losses, create severe accidents at power plants that will stop the supply of energy. All this disrupts the normal life and work of people.

To fight lightning, people sought to study it. Without knowledge, it was impossible to defeat lightning. “Everything is given by knowledge, victory is also given,” said Maxim Gorky.

In this short book, we will talk about how lightning and thunder occur, what harm lightning can do, and how to protect yourself from its destructive effects. Let's start with basic information about electricity, without which everything that follows will not be clear to the reader.

Two and a half thousand years ago, the Greek scientist Thales from the city of Miletus noticed that if amber (yellow resin used for decoration) is rubbed with fur, then it can attract light objects - for example, fibers or straws. In Greek, amber was called electron. From this word electricity got its name.

Then it was discovered that some other objects acquire the same properties as amber, for example, glass, ebonite (the substance from which combs, gramophone records, etc. are made), if they are rubbed with wool, silk or fur. Then they say that these objects are electrified.

An ebony comb can be electrified by combing hair with it. Anyone who saw how cleanly washed and dry hair was combed in the dark with a comb noticed bluish sparks and heard their crackling.

One of the first machines that man built to generate electricity (this was at the end of the 17th century) consisted of a glass ball rotating on an iron axis. When a rotating ball was rubbed with cloth and then touched with a hand, a light was visible between the ball and the hand in the darkness and a crackling sound was heard. With the rapid rotation of the ball, weak sparks were observed. At first it seems surprising that these small, weak sparks and their slight crackle have the same origin as the huge dazzling lightning and the thunder that accompanies it. But that's just the way it is. Already 200 years ago, scientists finally established that lightning is an electric spark.

This was first proved in 1752 by the famous American scientist and public figure Benjamin Franklin.

In the summer of 1752, a strange picture could be observed in the American city of Philadelphia. Climbing under the canopy, two adults (the eldest looked about 45 years old, the other was just a young man) launched a silk kite. It was Franklin and his son. The father and son tied a massive iron key to the garden gate to the end of the kite string, attached to the post with a silk ribbon (Fig. 1). Only the son was dedicated by the father to the secret of his experiments, fearing, in case of their failure, stinging ridicule. He stood uneasily by the kite, waiting for the results of the experiment, as a verdict on his many years of research.

Rice. 1. Franklin and his son launch a kite. (From an old painting.)

A cloud came up and passed by. No results, no traces of electricity ... And suddenly the fibers of the lace stretched, as happened during experiments with electricity conducted by scientists in the laboratory. Franklin quickly put his finger to the key and ... the concussion that he received from the strong electric spark that had slipped through at the same time seemed to him the most pleasant of sensations.

After all, he achieved what he so passionately and stubbornly desired! His discovery excited the entire scientific world of that time. A pale spark that made a soft crack sounded like thunder to the whole world, proving that lightning is an electrical discharge. Franklin, as it were, brought lightning down to the earth, taking it away from the mysterious "unearthly forces." + ", and the negative sign" – ". Such designations will be used in the figures of this book.