Who discovered induction. The discovery of electromagnetic induction made the emergence possible. The phenomenon of electromagnetic induction. Discovery, experience, application

So far, we have considered electric and magnetic fields that do not change with time. It was found out that electric field created electric charges, and the magnetic field - moving charges, i.e. electric current. Let's move on to getting acquainted with electric and magnetic fields, which change with time.

The most important fact that has been discovered is the closest relationship between electric and magnetic fields. A time-varying magnetic field generates an electric field, and a changing electric field generates a magnetic field. Without this connection between the fields, the variety of manifestations electromagnetic forces would not be as extensive as it really is. There would be no radio waves or light.

It is no coincidence that the first, decisive step in the discovery of new properties of electromagnetic interactions was made by the founder of the ideas about the electromagnetic field - Faraday. Faraday was confident in the unified nature of electrical and magnetic phenomena. Thanks to this, he made a discovery, which later formed the basis for the design of generators of all power plants in the world, converting mechanical energy into energy. electric current. (Other sources: galvanic cells, batteries, etc. - provide a negligible share of the generated energy.)

Electric current, Faraday reasoned, is capable of magnetizing a piece of iron. Could a magnet in turn cause an electric current?

For a long time, this connection could not be found. It was difficult to think of the main thing, namely: only a moving magnet or a magnetic field changing in time can excite an electric current in the coil.

What kind of accidents could prevent the discovery, shows the following fact. Almost simultaneously with Faraday, the Swiss physicist Colladon was trying to get an electric current in a coil using a magnet. When working, he used a galvanometer, the light magnetic needle of which was placed inside the coil of the device. To prevent the magnet from exerting a direct influence on the needle, the ends of the coil, into which Colladon pushed the magnet, hoping to get a current in it, were led into the next room and connected there to the galvanometer. Having inserted the magnet into the coil, Colladon went into the next room and, with chagrin,

made sure that the galvanometer does not show current. If only he had watched the galvanometer all the time and asked someone to work on the magnet, a remarkable discovery would have been made. But this did not happen. A magnet at rest relative to a coil causes no current in it.

Phenomenon electromagnetic induction consists in the occurrence of an electric current in a conducting circuit, which either rests in a magnetic field that changes in time, or moves in a constant magnetic field in such a way that the number of magnetic induction lines penetrating the circuit changes. It was discovered on August 29, 1831. It is a rare case when the date of a new remarkable discovery is known so precisely. Here is a description of the first experiment given by Faraday himself:

“Wound on a wide wooden coil copper wire 203 feet long, and between the turns of it is wound a wire of the same length, but insulated from the first cotton thread. One of these spirals was connected to a galvanometer, and the other to a strong battery consisting of 100 pairs of plates ... When the circuit was closed, it was possible to notice a sudden, but extremely weak action on the galvanometer, and the same was noticed when the current stopped. With the continuous passage of current through one of the coils, it was not possible to note any effect on the galvanometer, or in general any inductive effect on the other coil, despite the fact that the heating of the entire coil connected to the battery, and the brightness of the spark jumping between the coals, testified to battery power "(Faraday M. " Experimental studies on electricity", 1st series).

So, initially, induction was discovered in conductors that were motionless relative to each other during the closing and opening of the circuit. Then, clearly understanding that the approach or removal of conductors with current should lead to the same result as the closing and opening of the circuit, Faraday proved through experiments that the current arises when the coils move each other.

relative to a friend. Familiar with the works of Ampère, Faraday understood that a magnet is a collection of small currents circulating in molecules. On October 17, as recorded in his laboratory journal, an induction current was detected in the coil during the insertion (or withdrawal) of the magnet. Within one month, Faraday experimentally discovered all the essential features of the phenomenon of electromagnetic induction.

At present, Faraday's experiments can be repeated by everyone. To do this, you need to have two coils, a magnet, a battery of elements and a sufficiently sensitive galvanometer.

In the installation shown in Figure 238, an induction current occurs in one of the coils when the electrical circuit of the other coil, which is stationary relative to the first, is closed or opened. In the installation in Figure 239, a rheostat changes the current in one of the coils. In Figure 240, a, the induction current appears when the coils move relative to each other, and in Figure 240, b - when the permanent magnet moves relative to the coil.

Faraday himself already grasped the common thing that determines the appearance of an induction current in experiments that look different outwardly.

In a closed conducting circuit, a current arises when the number of magnetic induction lines penetrating the area bounded by this circuit changes. And the faster the number of lines of magnetic induction changes, the greater the resulting induction current. In this case, the reason for the change in the number of lines of magnetic induction is completely indifferent. This can be a change in the number of lines of magnetic induction penetrating the area of a fixed conductive circuit due to a change in the current strength in an adjacent coil (Fig. 238), and a change in the number of lines of induction due to the movement of the circuit in an inhomogeneous magnetic field, the density of lines of which varies in space (Fig. 241).

Lesson topic:

Discovery of electromagnetic induction. magnetic flux.

Target: introduce students to the phenomenon of electromagnetic induction.

During the classes

I. Organizational moment

II. Knowledge update.

1. Frontal survey.

What is Ampère's hypothesis?
What is magnetic permeability?
What substances are called para- and diamagnets?
What are ferrites?
Where are ferrites used?
How do you know that there is a magnetic field around the Earth?
Where are the North and South magnetic poles of the Earth?
What processes take place in the Earth's magnetosphere?
What is the reason for existence magnetic field at the earth?

2. Analysis of experiments.

Experiment 1

The magnetic needle on the stand was brought to the lower and then to the upper end of the tripod. Why does the arrow turn towards the lower end of the tripod from either side south pole, and to the upper end - the northern end?(All iron objects are in the Earth's magnetic field. Under the influence of this field, they are magnetized, and the lower part of the object detects the north magnetic pole, and the top - the south.)

Experiment 2

In a large cork stopper, make a small groove for a piece of wire. Lower the cork into the water, and put the wire on top, placing it along the parallel. In this case, the wire, together with the cork, is rotated and installed along the meridian. Why?(The wire has been magnetized and is set in the Earth's field like a magnetic needle.)

III. Learning new material

There are magnetic forces between moving electric charges. Magnetic interactions are described based on the concept of a magnetic field that exists around moving electric charges. Electric and magnetic fields are generated by the same sources - electric charges. It can be assumed that there is a connection between them.

In 1831, M. Faraday confirmed this experimentally. He discovered the phenomenon of electromagnetic induction (slides 1.2).

Experiment 1

We connect the galvanometer to the coil, and we will put forward from it permanent magnet. We observe the deviation of the galvanometer needle, a current (induction) has appeared (slide 3).

The current in the conductor occurs when the conductor is in the area of \u200b\u200bthe alternating magnetic field (slide 4-7).

Faraday represented an alternating magnetic field as a change in the number of lines of force penetrating the surface bounded by a given contour. This number depends on the induction AT magnetic field, from the contour area S and its orientation in the given field.

F \u003d BS cos a - magnetic flux.

F [Wb] Weber (slide 8)

The induction current can have different directions, which depend on whether the magnetic flux penetrating the circuit decreases or increases. The rule for determining the direction of the induced current was formulated in 1833. E. X. Lenz.

Experiment 2

We slide a permanent magnet into a light aluminum ring. The ring is repelled from it, and when extended, it is attracted to the magnet.

The result does not depend on the polarity of the magnet. Repulsion and attraction is explained by the appearance of an induction current in it.

When the magnet is pushed in, the magnetic flux through the ring increases: the repulsion of the ring at the same time shows that the induction current in it has such a direction in which the induction vector of its magnetic field is opposite in direction to the induction vector of the external magnetic field.

Lenz's rule:

The inductive current always has such a direction that its magnetic field prevents any changes in the magnetic flux that cause the appearance of an inductive current.(slide 9).

IV. Conducting laboratory work

Laboratory work on the topic "Experimental verification of the Lenz rule"

Devices and materials:milliammeter, coil-coil, arcuate magnet.

Working process

Prepare a table.

After the discoveries of Oersted and Ampère, it became clear that electricity has a magnetic force. Now it was necessary to confirm the influence of magnetic phenomena on electrical ones. This problem was brilliantly solved by Faraday.

Michael Faraday (1791-1867) was born in London, one of the poorest parts of it. His father was a blacksmith, and his mother was the daughter of a tenant farmer. When Faraday reached school age He was sent to elementary school. The course taken by Faraday here was very narrow and limited only to teaching reading, writing, and the beginning of counting.

A few steps from the house where the Faraday family lived, there was a bookstore, which was also a bookbinding establishment. This is where Faraday got to, having completed the course elementary school when the question arose about choosing a profession for him. Michael at that time was only 13 years old. Already in his youth, when Faraday had just begun his self-education, he strove to rely solely on facts and verify the reports of others with his own experiences.

These aspirations dominated him all his life as the main features of his scientific activity Physical and chemical experiments Faraday began to do it as a boy at the first acquaintance with physics and chemistry. Once Michael attended one of the lectures of Humphrey Davy, the great English physicist.

Faraday made a detailed note of the lecture, bound it, and sent it to Davy. He was so impressed that he offered Faraday to work with him as a secretary. Soon Davy went on a trip to Europe and took Faraday with him. For two years they visited the largest European universities.

Returning to London in 1815, Faraday began working as an assistant in one of the laboratories of the Royal Institution in London. At that time it was one of the best physical laboratories in the world. From 1816 to 1818 Faraday published a number of small notes and small memoirs on chemistry. Faraday's first work on physics dates back to 1818.

Based on the experiences of his predecessors and combining several of his own experiences, by September 1821, Michael had printed the "Success Story of Electromagnetism". Already at that time, he made up a completely correct concept of the essence of the phenomenon of deflection of a magnetic needle under the action of a current.

Having achieved this success, Faraday left his studies in the field of electricity for ten years, devoting himself to the study of a number of subjects of a different kind. In 1823, Faraday made one of the most important discoveries in the field of physics - he first achieved the liquefaction of a gas, and at the same time established a simple but valid method for converting gases into a liquid. In 1824, Faraday made several discoveries in the field of physics.

Among other things, he established the fact that light affects the color of glass, changing it. AT next year Faraday again turns from physics to chemistry, and the result of his work in this area is the discovery of gasoline and sulfuric naphthalene acid.

In 1831, Faraday published a treatise On a Special Kind of Optical Illusion, which served as the basis for a beautiful and curious optical projectile called the "chromotrope". In the same year, another treatise by the scientist "On vibrating plates" was published. Many of these works could by themselves immortalize the name of their author. But the most important of scientific works Faraday are his research in the field of electromagnetism and electrical induction.

Strictly speaking, the important branch of physics, which treats the phenomena of electromagnetism and inductive electricity, and which is currently of such great importance for technology, was created by Faraday out of nothing.

By the time Faraday finally devoted himself to research in the field of electricity, it was established that with ordinary conditions the presence of an electrified body is sufficient for its influence to excite electricity in every other body. At the same time, it was known that the wire through which the current passes and which is also an electrified body does not have any effect on other wires placed nearby.

What caused this exception? This is the question that interested Faraday and the solution of which led him to the most important discoveries in the field of induction electricity. As usual, Faraday began a series of experiments that were supposed to clarify the essence of the matter.

Faraday wound two insulated wires parallel to each other on the same wooden rolling pin. He connected the ends of one wire to a battery of ten elements, and the ends of the other to a sensitive galvanometer. When the current was passed through the first wire,

Faraday turned all his attention to the galvanometer, expecting to notice from its oscillations the appearance of a current in the second wire as well. However, there was nothing of the kind: the galvanometer remained calm. Faraday decided to increase the current and introduced 120 galvanic cells into the circuit. The result is the same. Faraday repeated this experiment dozens of times, all with the same success.

Anyone else in his place would have left the experiment, convinced that the current passing through the wire has no effect on the adjacent wire. But Faraday always tried to extract from his experiments and observations everything that they could give, and therefore, not having received a direct effect on the wire connected to the galvanometer, he began to look for side effects.

He immediately noticed that the galvanometer, remaining completely calm during the entire passage of the current, began to oscillate at the very closing of the circuit and at its opening. the second wire is also excited by a current, which in the first case is opposite to the first current and the same with it in the second case and lasts only one instant.

These secondary instantaneous currents, caused by the influence of primary ones, were called inductive by Faraday, and this name has been preserved for them until now. Being instantaneous, instantly disappearing after their appearance, inductive currents would have no practical value, if Faraday had not found a way, with the help of an ingenious device (switch), to constantly interrupt and again conduct the primary current coming from the battery through the first wire, due to which more and more inductive currents are continuously excited in the second wire, thus becoming constant. So a new source was found electrical energy, in addition to the previously known (friction and chemical processes), is induction, and the new kind of this energy is induction electricity.

Continuing his experiments, Faraday further discovered that a simple approximation of a wire twisted into a closed curve to another, along which a galvanic current flows, is enough to excite an inductive current in the direction opposite to the galvanic current in a neutral wire, that the removal of a neutral wire again excites an inductive current in it. the current is already in the same direction as the galvanic current flowing along a fixed wire, and that, finally, these inductive currents are excited only during the approach and removal of the wire to the conductor of the galvanic current, and without this movement, the currents are not excited, no matter how close the wires are to each other .

Thus, a new phenomenon was discovered, similar to the above-described phenomenon of induction during the closing and termination of the galvanic current. These discoveries in turn gave rise to new ones. If it is possible to produce an inductive current by closing and stopping the galvanic current, would not the same result be obtained from the magnetization and demagnetization of iron?

The work of Oersted and Ampère had already established the relationship between magnetism and electricity. It was known that iron becomes a magnet when an insulated wire is wound around it and a galvanic current passes through the latter, and that magnetic properties of this iron cease as soon as the current stops.

Based on this, Faraday came up with this kind of experiment: two insulated wires were wound around an iron ring; moreover, one wire was wound around one half of the ring, and the other around the other. A current from a galvanic battery was passed through one wire, and the ends of the other were connected to a galvanometer. And so, when the current closed or stopped, and when, consequently, the iron ring was magnetized or demagnetized, the galvanometer needle oscillated rapidly and then quickly stopped, that is, all the same instantaneous inductive currents were excited in the neutral wire - this time: already under the influence of magnetism.

Thus, here for the first time magnetism was converted into electricity. Having received these results, Faraday decided to diversify his experiments. Instead of an iron ring, he began to use an iron band. Instead of exciting magnetism in iron with a galvanic current, he magnetized the iron by touching it to a permanent steel magnet. The result was the same: in the wire wrapped around the iron, always! the current was excited at the moment of magnetization and demagnetization of iron.

Then Faraday introduced a steel magnet into the wire spiral - the approach and removal of the latter caused in the wire induction currents. In a word, magnetism, in the sense of excitation of inductive currents, acted in exactly the same way as the galvanic current.

At that time, physicists were intensely occupied with one mysterious phenomenon, discovered in 1824 by Arago and did not find an explanation, despite; that this explanation was intensively sought by such eminent scientists of the time as Arago himself, Ampère, Poisson, Babaj and Herschel.

The matter was as follows. A magnetic needle, freely hanging, quickly comes to rest if a circle of non-magnetic metal is brought under it; if the circle is then put into rotational motion, the magnetic needle begins to follow it.

In a calm state, it was impossible to discover the slightest attraction or repulsion between the circle and the arrow, while the same circle, which was in motion, pulled behind it not only a light arrow, but also a heavy magnet. This truly miraculous phenomenon seemed to the scientists of that time a mysterious riddle, something beyond the natural.

Faraday, based on his above data, made the assumption that a circle of non-magnetic metal, under the influence of a magnet, is circulated during rotation by inductive currents that affect the magnetic needle and draw it behind the magnet.

Indeed, by introducing the edge of the circle between the poles of a large horseshoe-shaped magnet and connecting the center and edge of the circle with a galvanometer with a wire, Faraday received a constant electric current during the rotation of the circle.

Following this, Faraday settled on another phenomenon that was then causing general curiosity. As you know, if iron filings are sprinkled on a magnet, they are grouped along certain lines, called magnetic curves. Faraday, drawing attention to this phenomenon, gave the foundations in 1831 to magnetic curves, the name "lines of magnetic force", which then came into general use.

The study of these "lines" led Faraday to a new discovery, it turned out that for the excitation of inductive currents, the approach and removal of the source from magnetic pole are optional. To excite currents, it is enough to cross the lines of magnetic force in a known way.

Further works of Faraday in the mentioned direction acquired, from the modern point of view, the character of something completely miraculous. At the beginning of 1832, he demonstrated an apparatus in which inductive currents were excited without the help of a magnet or galvanic current.

The device consisted of an iron strip placed in a wire coil. This device, under ordinary conditions, did not give the slightest sign of the appearance of currents in it; but as soon as he was given a direction corresponding to the direction of the magnetic needle, a current was excited in the wire.

Then Faraday gave the position of the magnetic needle to one coil and then introduced an iron strip into it: the current was again excited. The reason that caused the current in these cases was terrestrial magnetism, which caused inductive currents like an ordinary magnet or galvanic current. In order to show and prove this more clearly, Faraday undertook another experiment that fully confirmed his ideas.

He reasoned that if a circle of non-magnetic metal, for example, copper, rotating in a position in which it intersects the lines of magnetic force of a neighboring magnet, gives an inductive current, then the same circle, rotating in the absence of a magnet, but in a position in which the circle will cross the lines of terrestrial magnetism, must also give an inductive current.

Indeed, a copper circle rotated in horizontal plane, gave an inductive current that produced a noticeable deviation of the galvanometer needle. Faraday completed a series of studies in the field of electrical induction with the discovery, made in 1835, of "the inductive effect of current on itself."

He found out that when a galvanic current is closed or opened, instantaneous inductive currents are excited in the wire itself, which serves as a conductor for this current.

The Russian physicist Emil Khristoforovich Lenz (1804-1861) gave a rule for determining the direction of the induced current. “The induction current is always directed in such a way that the magnetic field it creates impedes or slows down the movement that causes induction,” notes A.A. Korobko-Stefanov in his article on electromagnetic induction. - For example, when the coil approaches the magnet, the resulting inductive current has such a direction that the magnetic field created by it will be opposite to the magnetic field of the magnet. As a result, repulsive forces arise between the coil and the magnet.

Lenz's rule follows from the law of conservation and transformation of energy. If induction currents accelerated the movement that caused them, then work would be created from nothing. The coil itself, after a small push, would rush towards the magnet, and at the same time the induction current would release heat in it. In reality, the induction current is created due to the work of bringing the magnet and coil closer together.

Why is there an induced current? A deep explanation of the phenomenon of electromagnetic induction was given by the English physicist James Clerk Maxwell - the creator of the completed mathematical theory electromagnetic field.

To better understand the essence of the matter, consider a very simple experiment. Let the coil consist of one turn of wire and be pierced by an alternating magnetic field perpendicular to the plane of the turn. In the coil, of course, there is an induction current. Maxwell interpreted this experiment with exceptional courage and unexpectedness.

When the magnetic field changes in space, according to Maxwell, a process arises for which the presence of a wire coil is of no importance. The main thing here is the emergence of closed circle lines electric field covering a changing magnetic field. Under the action of the emerging electric field, electrons begin to move, and an electric current arises in the coil. A coil is just a device that allows you to detect an electric field.

The essence of the phenomenon of electromagnetic induction is that an alternating magnetic field always generates in the surrounding space an electric field with closed lines of force. Such a field is called a vortex field.

Research in the field of induction produced terrestrial magnetism, gave Faraday the opportunity to express the idea of the telegraph back in 1832, which then formed the basis of this invention. In general, the discovery of electromagnetic induction is not without reason attributed to the most outstanding discoveries of the 19th century - the work of millions of electric motors and electric current generators around the world is based on this phenomenon ...

Source of information: Samin D.K. “One Hundred Great scientific discoveries"., M.: "Veche", 2002

Today we will talk about the phenomenon of electromagnetic induction. We will reveal why this phenomenon was discovered and what benefits it brought.

Silk

People have always strived to live better. Someone might think that this is a reason to accuse humanity of greed. But often we are talking about finding basic household amenities.

AT medieval Europe They knew how to make woolen, cotton and linen fabrics. And at that time, people suffered from an excess of fleas and lice. At the same time, Chinese civilization has already learned how to skillfully weave silk. Clothes from it did not allow bloodsuckers to human skin. The paws of the insects slid over the smooth fabric, and the lice fell off. Therefore, the Europeans wanted to dress in silk at all costs. And the merchants thought it was another opportunity to get rich. Therefore, the Great Silk Road was laid.

Only in this way was the desired fabric delivered to suffering Europe. And so many people were involved in the process that cities sprang up, empires fought over the right to levy taxes, and some stretches of the road are still the most convenient way get to the right place.

Compass and star

Mountains and deserts stood in the way of caravans with silk. It happened that the character of the area remained the same for weeks and months. Steppe dunes gave way to the same hills, one pass followed another. And people had to somehow navigate in order to deliver their valuable cargo.

The stars came first. Knowing what day it is and what constellations to expect, an experienced traveler could always determine where the south is, where the east is, and where to go. But people with a sufficient amount of knowledge have always been lacking. Yes, and then they did not know how to accurately count the time. Sunset, sunrise - that's all the landmarks. A snowstorm or a sandstorm overcast weather even the possibility of seeing the polar star was ruled out.

Then people (probably the ancient Chinese, but scientists are still arguing about this) realized that one mineral is always located in a certain way in relation to the cardinal points. This property was used to create the first compass. Before the discovery of the phenomenon of electromagnetic induction was far away, but a start had been made.

From compass to magnet

The very name "magnet" goes back to the toponym. Probably the first compasses were made from ore mined in the hills of Magnesia. This area is located in Asia Minor. And the magnets looked like black stones.

The first compasses were very primitive. Water was poured into a bowl or other container, a thin disk of floating material was placed on top. And a magnetized needle was placed in the center of the disk. One of its ends always pointed to the north, the other - to the south.

It is hard to even imagine that the caravan kept water for the compass while people were dying of thirst. But staying on track and letting people, animals, and goods get to safety was more important than a few separate lives.

Compasses made many trips and met with various natural phenomena. It is not surprising that the phenomenon of electromagnetic induction was discovered in Europe, although magnetic ore was originally mined in Asia. In this intricate way, the desire of Europeans to sleep more comfortably led to the most important discovery of physics.

Magnetic or electric?

In the early nineteenth century, scientists figured out how to get direct current. The first primitive battery was created. It was enough to send a stream of electrons through metal conductors. Thanks to the first source of electricity, a number of discoveries were made.

In 1820, the Danish scientist Hans Christian Oersted found out that the magnetic needle deviates next to the conductor included in the network. The positive pole of the compass is always located in a certain way with respect to the direction of the current. The scientist made experiments in all possible geometries: the conductor was above or below the arrow, they were located parallel or perpendicular. The result was always the same: the included current set the magnet in motion. Thus, the discovery of the phenomenon of electromagnetic induction was anticipated.

But the idea of scientists must be confirmed by experiment. Immediately after Oersted's experiment, the English physicist Michael Faraday asked himself the question: "Do the magnetic and electric fields simply influence each other, or are they more closely related?" The scientist was the first to test the assumption that if an electric field causes a magnetized object to deviate, then the magnet should generate a current.

The scheme of experience is simple. Now any student can repeat it. A thin metal wire was coiled in the shape of a spring. Its ends were connected to a device that recorded the current. When a magnet moved next to the coil, the arrow of the device showed the voltage of the electric field. Thus, Faraday's law of electromagnetic induction was derived.

Continuation of experiments

But that's not all the scientist has done. Since the magnetic and electric fields are closely related, it was necessary to find out how much.

To do this, Faraday brought current to one winding and pushed it inside another similar winding with a radius greater than the first. Again electricity was induced. Thus, the scientist proved: a moving charge generates both electric and magnetic fields at the same time.

It is worth emphasizing that we are talking about the movement of a magnet or a magnetic field inside a closed circuit of a spring. That is, the flow must change all the time. If this does not happen, no current is generated.

Formula

Faraday's law for electromagnetic induction is expressed by the formula

Let's decipher the characters.

ε stands for EMF or electromotive force. This quantity is a scalar (that is, not a vector) and it shows the work that some forces or laws of nature apply to create a current. It should be noted that work must be performed by non-electric phenomena.

Φ is the magnetic flux through a closed circuit. This value is the product of two others: the modulus of the magnetic induction vector B and the area of the closed loop. If the magnetic field acts on the contour not strictly perpendicular, then the cosine of the angle between the vector B and the normal to the surface is added to the product.

Consequences of discovery

This law was followed by others. Subsequent scientists established the dependence of the electric current on the power, resistance on the material of the conductor. New properties were studied, incredible alloys were created. Finally, humanity has deciphered the structure of the atom, delved into the secret of the birth and death of stars, and opened the genome of living beings.

And all these accomplishments required a huge amount of resources, and, above all, electricity. Any production or large Scientific research were carried out where three components were available: qualified personnel, directly the material with which to work, and cheap electricity.

And this was possible where the forces of nature could impart a large moment of rotation to the rotor: rivers with a large elevation difference, valleys with strong winds, faults with an excess of geomagnetic energy.

It's interesting that modern way getting electricity does not differ fundamentally from Faraday's experiments. The magnetic rotor rotates very quickly inside a large coil of wire. The magnetic field in the winding changes all the time and an electric current is generated.

Of course, selected best material for the magnet and conductors, and the technology of the whole process is completely different. But the essence is one thing: a principle is used that is open on the simplest system.

After discoveries Oersted and Ampere it became clear that electricity has a magnetic force. Now it was necessary to confirm the influence of magnetic phenomena on electrical ones. This problem was brilliantly solved by Faraday.

Michael Faraday (1791-1867) was born in London, one of the poorest parts of it. His father was a blacksmith, and his mother was the daughter of a tenant farmer. When Faraday reached school age, he was sent to elementary school. The course taken by Faraday here was very narrow and limited only to teaching reading, writing, and the beginning of counting.

A few steps from the house where the Faraday family lived, there was a bookstore, which was also a bookbinding establishment. This is where Faraday got to, having completed the course of elementary school, when the question arose about choosing a profession for him. Michael at that time was only 13 years old. Already in his youth, when Faraday had just begun his self-education, he strove to rely solely on facts and verify the reports of others with his own experiences.

These aspirations dominated him all his life as the main features of his scientific activity. Faraday began to make physical and chemical experiments as a boy at the first acquaintance with physics and chemistry. Once Michael attended one of the lectures Humphrey Davy, the great English physicist.

Drawing on the experiences of his predecessors and combining several of his own experiences, by September 1821 Michael had printed "The success story of electromagnetism". Already at that time, he made up a completely correct concept of the essence of the phenomenon of deflection of a magnetic needle under the action of a current.

Among other things, he established the fact that light affects the color of glass, changing it. The following year, Faraday again turns from physics to chemistry, and the result of his work in this area is the discovery of gasoline and sulfuric naphthalene acid.

In 1831, Faraday published a treatise On a Special Kind of Optical Illusion, which served as the basis for a beautiful and curious optical projectile called the "chromotrope". In the same year, another treatise by the scientist "On vibrating plates" was published. Many of these works could by themselves immortalize the name of their author. But the most important of Faraday's scientific works are his studies in the field of electronics. electromagnetism and electrical induction.

By the time Faraday finally devoted himself to research in the field of electricity, it was established that, under ordinary conditions, the presence of an electrified body is sufficient for its influence to excite electricity in any other body. At the same time, it was known that the wire through which the current passes and which is also an electrified body does not have any effect on other wires placed nearby.

These secondary instantaneous currents, caused by the influence of primary ones, were called inductive by Faraday, and this name has been preserved for them until now. Being instantaneous, instantly disappearing after their appearance, inductive currents would have no practical significance if Faraday had not found a way, with the help of an ingenious device (commutator), to constantly interrupt and again conduct the primary current coming from the battery through the first wire, due to which in the second wire is continuously excited by more and more inductive currents, thus becoming constant. Thus, a new source of electrical energy was found, in addition to the previously known (friction and chemical processes), - induction, and a new type of this energy - induction electricity.

The work of Oersted and Ampère had already established the relationship between magnetism and electricity. It was known that iron became a magnet when an insulated wire was wound around it and a galvanic current passed through it, and that the magnetic properties of this iron ceased as soon as the current ceased.

Then Faraday introduced a steel magnet into the wire spiral - the approach and removal of the latter caused induction currents in the wire. In a word, magnetism, in the sense of excitation of inductive currents, acted in exactly the same way as the galvanic current.