Electromagnetic induction induced current. Faraday. discovery of electromagnetic induction. Magnetic or electric

A new period in the development of physical science begins with the ingenious discovery of Faraday electromagnetic induction. It was in this discovery that the ability of science to enrich technology with new ideas was clearly demonstrated. Based on his discovery, Faraday himself foresaw the existence of electromagnetic waves. On March 12, 1832, he sealed an envelope with the inscription "New Views to be kept in a sealed envelope in the archives of the Royal Society for the present time." This envelope was opened in 1938. It turned out that Faraday quite clearly understood that inductive actions propagate at a finite speed in a wave manner. “I believe it is possible to apply the theory of oscillations to the propagation of electrical induction,” wrote Faraday. At the same time, he pointed out that “the propagation of a magnetic influence takes time, i.e., when a magnet acts on another distant magnet or piece of iron, the influencing cause (which I dare to call magnetism) spreads from magnetic bodies gradually and requires a certain time for its propagation , which will obviously turn out to be very insignificant. I also believe that electrical induction propagates in exactly the same way. I believe that the propagation of magnetic forces from a magnetic pole is similar to the oscillation of a disturbed surface of water or to the sound vibrations of air particles."

Faraday understood the importance of his idea and, not being able to test it experimentally, decided with the help of this envelope “to secure the discovery for himself and, thus, have the right, in case of experimental confirmation, to declare this date as the date of his discovery.” So, on March 12, 1832, humanity first came to the idea of existence electromagnetic waves. From this date the history of discovery begins radio.

But Faraday's discovery was important not only in the history of technology. It had a huge impact on the development of scientific understanding of the world. With this discovery, a new object enters physics - physical field. Thus, Faraday's discovery belongs to those fundamental scientific discoveries that leave a noticeable mark on the entire history of human culture.

London blacksmith's son bookbinder born in London on September 22, 1791. The self-taught genius did not even have the opportunity to finish primary school and paved the way to science himself. While studying bookbinding, he read books, especially on chemistry, and performed chemical experiments himself. Listening to public lectures by the famous chemist Davy, he was finally convinced that his vocation was science, and turned to him with a request to hire him at the Royal Institution. From 1813, when Faraday was admitted to the institute as a laboratory assistant, until his death (August 25, 1867), he lived by science. Already in 1821, when Faraday received electromagnetic rotation, he set as his goal "to convert magnetism into electricity." Ten years of search and hard work culminated in the discovery of electromagnetic induction on August 29, 1871.

"Two hundred and three feet of copper wire in one piece were wound around a large wooden drum; another two hundred and three feet of the same wire was insulated in a spiral between the turns of the first winding, the metallic contact being eliminated by means of a cord. One of these spirals was connected to a galvanometer, and the other with a well-charged battery of one hundred pairs of four-inch square plates with double copper plates, when the contact was closed, there was a temporary but very weak effect on the galvanometer, and a similar slight effect took place when the contact with the battery was opened.” This is how Faraday described his first experiment on the induction of currents. He called this type of induction voltaic induction. He further describes his main experience with the iron ring - the prototype of the modern transformer.

"A ring was welded from a round piece of soft iron; the thickness of the metal was seven-eighths of an inch, and the outer diameter of the ring six inches. Around one part of this ring were wound three spirals, each containing about twenty-four feet of copper wire, one twentieth of an inch thick. The spirals were insulated from the iron and from each other..., occupying approximately nine inches along the length of the ring. They could be used individually and in connection, this group is designated by the letter A. About sixty feet of the same were wound on the other part of the ring in the same way. copper wire in two pieces, which formed a spiral B, having the same direction as the spirals A, but separated from them at each end by about half an inch of bare iron.

Spiral B was connected by copper wires to a galvanometer placed three feet from the iron. The individual spirals were connected end to end so as to form a common spiral, the ends of which were connected to a battery of ten pairs of plates four inches square. The galvanometer reacted immediately, and much more strongly than was observed, as described above, using a coil ten times more powerful, but without iron; however, despite maintaining contact, the action ceased. When the contact with the battery was opened, the arrow again deflected strongly, but in the direction opposite to that which was induced in the first case."

Faraday further investigated the influence of iron by direct experiment, introducing an iron rod inside a hollow coil, in this case “the induced current had a very strong effect on the galvanometer.” "A similar effect was then obtained with the help of ordinary magnets". Faraday called this action magnetoelectric induction, assuming that the nature of voltaic and magnetoelectric induction is the same.

All the experiments described constitute the content of the first and second sections of Faraday’s classic work “Experimental Research in Electricity,” begun on November 24, 1831. In the third section of this series, “On the New Electric State of Matter,” Faraday for the first time tries to describe the new properties of bodies manifested in electromagnetic induction. He calls this property he discovered the “electrotonic state.” This is the first germ of the field idea, which was later formed by Faraday and first precisely formulated by Maxwell. The fourth section of the first series is devoted to the explanation of the Arago phenomenon. Faraday correctly classifies this phenomenon as induction and tries to use this phenomenon to “obtain a new source of electricity.” When a copper disk moved between the poles of a magnet, it received a current in the galvanometer using sliding contacts. This was the first dynamo. Faraday summarizes the results of his experiments in the following words: “It has thus been shown that a constant current of electricity can be created by means of an ordinary magnet.” From his experiments on induction in moving conductors, Faraday derived the relationship between the polarity of a magnet, the moving conductor and the direction of the induced current, i.e., “the law governing the production of electricity through magnetoelectric induction.” As a result of his research, Faraday established that “the ability to induce currents is manifested in a circle around the magnetic resultant or force axis in exactly the same way as magnetism located around a circle arises around an electric current and is detected by it” *.

* (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 57.)

In other words, a vortex electric field arises around an alternating magnetic flux, just as a vortex magnetic field arises around an electric current. This fundamental fact was summarized by Maxwell in the form of his two electromagnetic field equations.

The second series of “Research”, begun on January 12, 1832, is also devoted to the study of the phenomena of electromagnetic induction, especially the inductive action of the Earth’s magnetic field. Faraday devotes the third series, begun on January 10, 1833, to proving the identity of various types of electricity: electrostatic, galvanic, animal , magnetoelectric (i.e., obtained through electromagnetic induction). Faraday comes to the conclusion that electricity obtained by different methods is qualitatively the same, the difference in actions is only quantitative. This dealt the final blow to the concept of various “fluids” of resin and glass electricity, galvanism, animal electricity. Electricity turned out to be a single, but polar entity.

The fifth series of Faraday's Researches, begun on June 18, 1833, is very important. Here Faraday begins his research on electrolysis, which led him to the establishment of the famous laws that bear his name. These studies were continued in the seventh series, begun on January 9, 1834. In this last series, Faraday proposes new terminology: he proposes to call the poles that supply current to the electrolyte electrodes, call positive electrode anode, and negative - cathode, particles of deposited substance going to the anode he calls anions, and the particles going to the cathode are cations. Further, he owns the terms electrolyte for degradable substances, ions And electrochemical equivalents. All these terms are firmly established in science. Faraday draws the correct conclusion from the laws he found that we can talk about some absolute quantity electricity associated with atoms of ordinary matter. “Although we know nothing about what an atom is,” writes Faraday, “we involuntarily imagine some small particle that appears to our mind when we think about it; however, in the same or even greater ignorance we are in relation to electricity, we are not even able to say whether it represents a special matter or matter, or simply the movement of ordinary matter, or another type of force or agent; nevertheless, there is a huge number of facts that make us think, that the atoms of matter are in some way endowed with or connected with electrical forces, and to them they owe their most remarkable qualities, including their chemical affinity for each other."

* (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 335.)

Thus, Faraday clearly expressed the idea of \u200b\u200bthe “electrification” of matter, the atomic structure of electricity, and the atom of electricity, or, as Faraday puts it, “the absolute amount of electricity,” turns out to be "just as definite in its action, like any of those quantities which, remaining connected with the particles of matter, impart to them their chemical affinity." The elementary electric charge, as further development of physics has shown, can indeed be determined from Faraday's laws.

The ninth series of Faraday's Studies was very important. This series, begun on December 18, 1834, dealt with the phenomena of self-induction, with extra currents of closure and opening. Faraday points out when describing these phenomena that although they have features inertia, However, the phenomenon of self-induction is distinguished from mechanical inertia by the fact that they depend on forms conductor. Faraday notes that "extract is identical with ... induced current" *. As a result, Faraday developed an idea of the very broad significance of the induction process. In the eleventh series of his studies, begun on November 30, 1837, he states: “Induction plays the most general role in all electrical phenomena, participating, apparently, in each of them, and in fact bears the features of a primary and essential principle” ** . In particular, according to Faraday, every charging process is an induction process, offsets opposite charges: “substances cannot be charged absolutely, but only relatively, according to a law identical with induction. Every charge is supported by induction. All phenomena voltage include the beginning of inductions" ***. The meaning of these statements by Faraday is that any electric field ("voltage phenomenon" - in Faraday's terminology) is necessarily accompanied by an induction process in the medium ("displacement" - in Maxwell's later terminology). This process is determined by the properties of the medium , its “inductive ability”, in Faraday’s terminology, or “dielectric constant”, in modern terminology. Faraday’s experiments with a spherical capacitor determined the dielectric constant of a number of substances with respect to air. These experiments strengthened Faraday’s idea of the essential role of the medium in electromagnetic processes.

* (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 445.)

** (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 478.)

*** (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 487.)

The law of electromagnetic induction was significantly developed by a Russian physicist of the St. Petersburg Academy Emilie Christianovich Lentz(1804-1865). On November 29, 1833, Lenz reported to the Academy of Sciences his research “On determining the direction of galvanic currents excited by electrodynamic induction.” Lenz showed that Faraday's magnetoelectric induction is closely related to Ampere's electromagnetic forces. “The position by which the magnetoelectric phenomenon is reduced to the electromagnetic one is as follows: if a metal conductor moves close to a galvanic current or magnet, then a galvanic current is excited in it in such a direction that if the conductor were stationary, the current could cause it to move in the opposite direction; it is assumed that a conductor at rest can move only in the direction of movement or in the opposite direction" *.

* (E. H. Lenz, Selected Works, Ed. Academy of Sciences of the USSR, 1950, pp. 148-149.)

This Lenz principle reveals the energetics of induction processes and played an important role in Helmholtz’s work on establishing the law of conservation of energy. Lenz himself derived from his rule the well-known principle in electrical engineering of the reversibility of electromagnetic machines: if you rotate a coil between the poles of a magnet, it generates a current; on the contrary, if a current is sent into it, it will rotate. An electric motor can be turned into a generator and vice versa. While studying the action of magnetoelectric machines, Lenz discovered the armature reaction in 1847.

In 1842-1843. Lenz produced a classic study “On the laws of heat release by galvanic current” (reported on December 2, 1842, published in 1843), which he began long before Joule’s similar experiments (Joule’s report appeared in October 1841) and continued by him despite the publication Joule, “since the latter’s experiments may meet with some justified objections, as has already been shown by our colleague Mr. Academician Hess” *. Lenz measures the current using a tangent compass, a device invented by Helsingfors professor Johann Nervander (1805-1848), and in the first part of his report examines this device. In the second part, “Heat Release in Wires,” reported on August 11, 1843, he arrives at his famous law:

Heating of the wire by galvanic current is proportional to the resistance of the wire.
Heating of a wire by galvanic current is proportional to the square of the current used for heating"**.

* (E. H. Lenz, Selected Works, Ed. USSR Academy of Sciences, 1950, p. 361.)

** (E. H. Lenz, Selected Works, Ed. USSR Academy of Sciences, 1950, p. 441.)

The Joule-Lenz law played an important role in establishing the law of conservation of energy. The entire development of the science of electrical and magnetic phenomena led to the idea of the unity of the forces of nature, to the idea of preserving these “forces”.

Almost simultaneously with Faraday, electromagnetic induction was observed by an American physicist Joseph Henry(1797-1878). Henry made a large electromagnet (1828) which, powered by a low-resistance galvanic cell, supported a load of 2,000 pounds. Faraday mentions this electromagnet and points out that with its help you can get a strong spark when opened.

Henry was the first to observe (1832) the phenomenon of self-induction, and his priority is marked by the name of the unit of self-induction “Henry”.

In 1842 Henry established oscillatory character Leyden jar type. The thin glass needle with which he studied this phenomenon was magnetized with different polarities, while the direction of the discharge remained unchanged. “The discharge, whatever its nature,” Henry concludes, “does not seem (using Franklin’s theory. - P.K.) to be a single transfer of weightless fluid from one plate to another; the discovered phenomenon forces us to assume the existence of the main discharge in one direction, and then several strange movements back and forth, each weaker than the last, continuing until equilibrium is achieved."

Induction phenomena are becoming a leading topic in physical research. In 1845, a German physicist Franz Neumann(1798-1895) gave the mathematical expression law of induction, summarizing the research of Faraday and Lenz.

The electromotive force of induction was expressed by Neumann in the form of a time derivative of some function inducing the current and the mutual configuration of interacting currents. Neumann called this function electrodynamic potential. He also found an expression for the coefficient of mutual induction. In his essay “On the Conservation of Force” in 1847, Helmholtz derived Neumann’s expression for the law of electromagnetic induction from energy considerations. In the same work, Helmholtz states that the discharge of a capacitor is “not... a simple movement of electricity in one direction, but... its flow in one direction or the other between two plates in the form of oscillations that become smaller and smaller. less, until finally all living force is destroyed by the sum of resistances."

In 1853 William Thomson(1824-1907) gave a mathematical theory of the oscillatory discharge of a capacitor and established the dependence of the oscillation period on the parameters of the oscillatory circuit (Thomson's formula).

In 1858 P. Blazerna(1836-1918) experimentally recorded the resonant curve of electrical oscillations, studying the effect of a discharge-inducing circuit containing a bank of capacitors and connecting conductors to a side circuit, with a variable length of the induced conductor. Also in 1858 Wilhelm Feddersen(1832-1918) observed the spark discharge of a Leyden jar in a rotating mirror, and in 1862 he photographed an image of a spark discharge in a rotating mirror. Thus, the oscillatory nature of the discharge was clearly established. At the same time, Thomson's formula was tested experimentally. Thus, step by step, the doctrine of electrical vibrations, constituting the scientific foundation of alternating current electrical engineering and radio engineering.

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

The most important fact that was discovered is the close 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 fields, the variety of manifestations of electromagnetic forces would not be as extensive as they actually are. 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 taken by the founder of the concept of the electromagnetic field - Faraday. Faraday was confident in the unified nature of electrical and magnetic phenomena. Thanks to this, he made a discovery, which subsequently formed the basis for the design of generators for all power plants in the world, converting mechanical energy into electrical energy. (Other sources: galvanic cells, batteries, etc. - provide an insignificant share of the generated energy.)

An electric current, Faraday reasoned, can magnetize a piece of iron. Couldn't a magnet, in turn, cause an electric current?

For a long time this connection could not be discovered. It was difficult to figure out the main thing, namely: only a moving magnet or a time-varying magnetic field can excite an electric current in a coil.

The following fact shows what kind of accidents could have prevented the discovery. Almost simultaneously with Faraday, the Swiss physicist Colladon tried to obtain 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. So that the magnet did not have a direct effect on the needle, the ends of the coil into which Colladon pushed the magnet, hoping to receive a current in it, were brought into the next room and there connected to a galvanometer. Having inserted the magnet into the coil, Colladon walked into the next room and, with chagrin,

I made sure that the galvanometer did not show any current. If he had only to watch the galvanometer all the time and ask someone to work on the magnet, a remarkable discovery would have been made. But this did not happen. A magnet at rest relative to the coil does not generate current in it.

The phenomenon of electromagnetic induction consists in the occurrence of an electric current in a conducting circuit, which is either at rest in a time-varying magnetic field 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 accurately. Here is a description of the first experiment given by Faraday himself:

“A copper wire 203 feet long was wound on a wide wooden spool, and between its turns was wound a wire of the same length, but insulated from the first with a 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, a sudden but extremely weak action was noticed on the galvanometer, and the same was noticed when the current stopped. With the continuous passage of current through one of the spirals, it was not possible to notice either an effect on the galvanometer, or at all any inductive effect on the other spiral, despite the fact that the heating of the entire spiral connected to the battery and the brightness of the spark jumping between the coals indicated battery power" (Faraday M. "Experimental Research in Electricity", 1st series).

So, initially, induction was discovered in conductors that are motionless relative to each other when closing and opening a circuit. Then, clearly understanding that bringing current-carrying conductors closer or further away should lead to the same result as closing and opening a circuit, Faraday proved through experiments that current arises when the coils move each other

regarding a friend. Familiar with the works of Ampere, Faraday understood that a magnet is a collection of small currents circulating in molecules. On October 17, as recorded in his laboratory notebook, an induced current was detected in the coil while the magnet was being pushed in (or pulled out). Within one month, Faraday experimentally discovered all the essential features of the phenomenon of electromagnetic induction.

Nowadays, everyone can repeat Faraday's experiments. To do this, you need to have two coils, a magnet, a battery of elements and a fairly sensitive galvanometer.

In the installation shown in Figure 238, an induction current occurs in one of the coils when the electrical circuit of another coil, stationary relative to the first, is closed or opened. In the installation in Figure 239, a rheostat is used to change the current strength 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 a permanent magnet moves relative to the coil.

Faraday himself already grasped the general thing on which the appearance of an induction current depends in experiments that outwardly look different.

In a closed conducting circuit, a current arises when the number of magnetic induction lines piercing the area limited by this circuit changes. And the faster the number of magnetic induction lines changes, the greater the resulting induction current. In this case, the reason for the change in the number of magnetic induction lines is completely indifferent. This may be a change in the number of magnetic induction lines penetrating the area of a stationary conducting circuit due to a change in the current strength in the adjacent coil (Fig. 238), or a change in the number of induction lines due to the movement of the circuit in a non-uniform magnetic field, the density of the lines of which varies in space (Fig. 241).

In 1821, Michael Faraday wrote in his diary: “Convert magnetism into electricity.” After 10 years, he solved this problem.
Faraday's discovery
It is no coincidence that the first and most important step in the discovery of new properties of electromagnetic interactions was taken by the founder of the concept of the electromagnetic field - Faraday. Faraday was confident in the unified nature of electrical and magnetic phenomena. Shortly after Oersted's discovery, he wrote: “... it seems very unusual that, on the one hand, every electric current is accompanied by a magnetic action of corresponding intensity, directed at right angles to the current, and that at the same time, in good conductors of electricity placed in the sphere of this action, no current was induced at all, no tangible action equivalent in strength to such a current arose. Hard work for ten years and faith in success led Faraday to a discovery that subsequently formed the basis for the design of generators for all power plants in the world, converting mechanical energy into electrical energy. (Sources operating on other principles: galvanic cells, batteries, thermal and photocells - provide an insignificant share of the generated electrical energy.)
For a long time, the relationship between electrical and magnetic phenomena could not be discovered. It was difficult to figure out the main thing: only a time-varying magnetic field can excite an electric current in a stationary coil, or the coil itself must move in a magnetic field.
The discovery of electromagnetic induction, as Faraday called this phenomenon, was made on August 29, 1831. It is a rare case when the date of a new remarkable discovery is so precisely known. Here is a brief description of the first experiment given by Faraday himself.
“A copper wire 203 feet long was wound on a wide wooden spool, and between its turns was wound a wire of the same length, but insulated from the first with 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, a sudden but extremely weak effect on the galvanometer was noticed, and the same was noticed when the current stopped. With the continuous passage of current through one of the spirals, it was not possible to note either an effect on the galvanometer, or at all any inductive effect on the other spiral, unable to 5.1
noting that the heating of the entire coil connected to the battery, and the brightness of the spark jumping between the coals, indicated the power of the battery.”
So, initially, induction was discovered in conductors that are motionless relative to each other when closing and opening a circuit. Then, clearly understanding that bringing current-carrying conductors closer or further away should lead to the same result as closing and opening a circuit, Faraday proved through experiments that current arises when the coils move relative to each other (Fig. 5.1). Familiar with the works of Ampere, Faraday understood that a magnet is a collection of small currents circulating in molecules. On October 17, as recorded in his laboratory notebook, an induced current was detected in the coil while the magnet was being pushed in (or pulled out) (Figure 5.2). Within one month, Faraday experimentally discovered all the essential features of the phenomenon of electromagnetic induction. All that remained was to give the law a strict quantitative form and completely reveal the physical nature of the phenomenon.
Faraday himself already grasped the general thing on which the appearance of an induction current depends in experiments that outwardly look different.
In a closed conducting circuit, a current arises when the number of magnetic induction lines penetrating the surface bounded by this circuit changes. And the faster the number of magnetic induction lines changes, the greater the resulting current. In this case, the reason for the change in the number of magnetic induction lines is completely indifferent. This can be a change in the number of lines of magnetic induction piercing a stationary conductor due to a change in the current strength in a neighboring coil, or a change in the number of lines due to the movement of the circuit in a non-uniform magnetic field, the density of the lines of which varies in space (Fig. 5.3).
Faraday not only discovered the phenomenon, but was also the first to construct an as yet imperfect model of an electric current generator that converts mechanical rotational energy into current. It was a massive copper disk rotating between the poles of a strong magnet (Fig. 5.4). By connecting the axis and edge of the disk to the galvanometer, Faraday discovered a deviation
IN
\

\
\
\
\
\
\
\L

S arrow pointing. The current was, however, weak, but the principle found made it possible to subsequently build powerful generators. Without them, electricity would still be a luxury available to few people.
An electric current arises in a conducting closed loop if the loop is in an alternating magnetic field or moves in a time-constant field so that the number of magnetic induction lines penetrating the loop changes. This phenomenon is called electromagnetic induction.

An example would be a question. In this context we can talk about taboos. There are certain areas that will be taboo for the majority, which does not mean that there will not be one, three, three scientists who will handle this phenomenon with the curiosity of a person.

These social conditions make most people uninterested in this. R: And that's just a question. The example of the fitting also shows the fear of not being discredited. Dr. Marek Spira: Today we strive to break all taboos. On the one hand, this is knowledge of the truth, and on the other, respect for certain values, the overthrow of which only leads to the destruction of social order. Human curiosity is so great that it transcends all boundaries. By nature, man does not like taboos. And in this sense, the desire for truth knows no boundaries, which exist, of course, but they are constantly moving.

A new period in the development of physical science begins with the ingenious discovery of Faraday electromagnetic induction. It was in this discovery that the ability of science to enrich technology with new ideas was clearly demonstrated. Faraday himself already foresaw, on the basis of his discovery, the existence of electromagnetic waves. On March 12, 1832, he sealed an envelope with the inscription "New Views to be kept in a sealed envelope in the archives of the Royal Society for the present time." This envelope was opened in 1938. It turned out that Faraday quite clearly understood that inductive actions propagate at a finite speed in a wave manner. “I believe it is possible to apply the theory of oscillations to the propagation of electrical induction,” wrote Faraday. At the same time, he pointed out that “the propagation of a magnetic influence takes time, i.e., when a magnet acts on another distant magnet or piece of iron, the influencing cause (which I dare to call magnetism) spreads from magnetic bodies gradually and requires a certain time for its propagation , which will obviously turn out to be very insignificant. I also believe that electrical induction propagates in exactly the same way. I believe that the propagation of magnetic forces from a magnetic pole is similar to the oscillation of a disturbed surface of water or to the sound vibrations of air particles."

This raises the question of whether we will ever know the full truth. Knowing human nature, we can say that although this is impossible, we will always strive for it. However, there is a danger that we will ignore this mystery. Being at a certain stage of knowledge, we can conclude that we already know everything. Meanwhile, disaster is coming, and the question is how can we let it go? Perhaps it was due to the neglect of the forces of nature, the forces of nature. An example would be the inventor of the computer, who in the last century believed that the acquisition of knowledge in a computer would be unlimited.

Years after this discovery, with laptops today, this was a fallacy. How the extent of our ignorance has increased as the number of questions has increased. We physicists shy away from the earth. Let's say we want to fly to a galaxy several light years away from Earth. Since we cannot build a spacecraft that travels faster than the speed of light, it will not take one generation of astronauts to reach this galaxy. Although it is possible to imagine space travel for many generations of astronauts, this is only possible in science fiction.

It is these constants, known to us today, that determine the limits of knowledge. If we consider the Big Bang, we must remember that our knowledge still does not reach the point that the density of matter is incomparable to what we are dealing with today and which we cannot reproduce in our conditions.

We don't know this "explosive" physics, so we don't know these physical constants if they existed. N.: We are also not sure that today's physics is final. We had Newton who was later tested by Einstein, so we can conclude that Einstein will be tested by someone else.

On this basis, the special theory of relativity was created, which has already been repeatedly confirmed experimentally. However, if one of these paradigms fails, we will have a new physics. If we say that we know the universe, nature, that we know that it happened before, we say this because the indicated physical constants do not change their values over time. Experiments that attempt to undermine these solids - and how and how they are carried out - are not convincing.

In fact, we can say that from a certain point we know that the physical laws governing the Universe have not changed - these constants are still the same. Are there secrets we don't want to face? Kant spoke of two types of metaphysics - metaphysics as a science that does not exist, and metaphysics as a natural tendency that makes us break taboos.

Limits exist, but the human mind has a natural need to ask questions that cannot be answered empirically. It is not a luxury, but a person's responsibility to find it. There was once a belief that too much curiosity leaves us short of God. We ourselves have created a taboo - God cannot be known because we will lose faith. Authentic people who are respected are first and foremost trusted, and their humility was conditioned by cultural context. The educated man began to walk away from God, claiming that he would not believe in this “superstition.”

There were many misunderstandings because sometimes we did not value the search for truth. Christianity has never officially declared such a formula, because faith needs the help of reason to know the truth and even argue with the Lord God. Can we really get to know him? This is another problem, but it does not relieve us of the responsibility of constantly searching, because we have a reason. The Church today repeats that there is no contradiction between faith and reason. Even if he defeats some dogmas?

S: We do not need to be afraid, reason cannot cancel any dogma, and if this happens, it means that we do not need to deal with dogma, but with the human formula without covering. The reason is to destroy lies, but truth never fails. We know this from the history of the Church, even if it was very difficult, the Church was able to cleanse itself of lies, and we are proud of that.

An illustration can be the example of the relationship between the crew of two spaceships, after the return of the crew of one of them it was said: there is no God, and the other is so beautiful that it can only be created by God. So, if there is a taboo at all, it is a temporary one due to cultural and social conditions, which is mainly due to the fear of dealing with something risky in terms of losing scientific position. This magic word - organization - has its origin, the question remains - what?

Therefore, God knows things as they are, and we are as they are. R: You may not agree with me, but something that cannot be verified experimentally will always be more difficult to accept. Especially in the field of physics. N.: The same Kant says: I have limited knowledge in order to make room for faith. Where there are boundaries of knowledge, my faith begins.

N: The reasons for this scientist are this: all the evidence for the existence of God was false, so there is no God. Meanwhile, only the methodology is tested as follows: all evidence for the existence of God was false, but no conclusions could be drawn about his existence or his existence. And this is really beyond the scope, but there is also a huge problem here - the correct research methodology: right or wrong, this applies to every field, be it physics, astronomy, philosophy or theology.

Why is it used to discover secrets - a natural need to advance knowledge, progress, or satisfy the subjective needs of individual researchers? This can be seen in the example of uninhibited so-called. basic research. Their nature is to discover the secrets of nature, regardless of the frequent stimulus for their immediate use. When Faraday discovered the phenomenon of electromagnetic induction, he was asked what it would be like to have humanity?

He said evasively that you will probably pay taxes and not address the scientific side of the discovery. His subjective need was the desire to know and the satisfaction that came from it. It seems to me that exploiting the usefulness of the study is not justified.

For every opening you need to be well prepared. Each discovery, even the so-called media catastrophe, is covered by the vast knowledge and experience of the researcher. Only great knowledge, imagination and going beyond the traditional framework of scientific research allows us to see something new, new, unknown, and then called discovery. Copernicus was condemned not because he did not like him, for example, he was from Toruń, but because he could not understand that the Bible cannot be read literally. Often the researcher is faced with a vulgar approach to learning, knowledge and misunderstanding.

Sometimes the discoverer is ahead of his time, only a new generation accepts his discovery. We also have a natural tendency today to comfortably layer the world in different directions, so that we don't have to think just to consume. An example is James Clerk Maxwell, whose famous equation is our civilization; Without them, it would be difficult to imagine today's successes and development. However, Maxwell's understanding of the mechanism of electromagnetic propagation does not fit into today's interpretation of this phenomenon.

In addition, Olivier Heaviside, another scientist and mathematician, made his mathematical and mathematical formulas very useful. This is an example of the essence and type of continuity of science: many scientists, even the “smallest,” contribute to universal knowledge. Isn’t this comforting in an era of yet another humiliation in the academic world? What are the secrets of modern science facing the greatest research opportunities?

Scientists still wonder why the charge of a proton is positive and the electron is negative? What properties does antimatter have? How does a material known to operate at very high temperatures behave? These questions really matter. We are talking about temperatures comparable to the internal temperature of the Sun. This is a huge problem for physicists, very important in the context of the search for new energy sources.

To illustrate the importance of this problem for humanity, it is enough to give one of the estimates. In a situation of such great progress in science, in the use of nature in the service of humanity, the problem remains with man who is becoming more and more confused. The changes are starting to blur. The unknown development of science does not have a negative impact on the intellectual development of societies, but on the contrary - negative phenomena, such as secondary illiteracy, are multiplying.

* (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 335.)

* (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 445.)

** (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 478.)

*** (M. Faraday, Experimental Research in Electricity, Vol. I, Ed. USSR Academy of Sciences, 1947, p. 487.)

* (E. H. Lenz, Selected Works, Ed. Academy of Sciences of the USSR, 1950, pp. 148-149.)

Heating of the wire by galvanic current is proportional to the resistance of the wire.
Heating of a wire by galvanic current is proportional to the square of the current used for heating"**.

* (E. H. Lenz, Selected Works, Ed. USSR Academy of Sciences, 1950, p. 361.)

** (E. H. Lenz, Selected Works, Ed. USSR Academy of Sciences, 1950, p. 441.)

Henry was the first to observe (1832) the phenomenon of self-induction, and his priority is marked by the name of the unit of self-induction “Henry”.

Answer:

The next important step in the development of electrodynamics after Ampere's experiments was the discovery of the phenomenon of electromagnetic induction. The phenomenon of electromagnetic induction was discovered by the English physicist Michael Faraday (1791 - 1867).

Faraday, while still a young scientist, like Oersted, thought that all the forces of nature are interconnected and, moreover, that they are capable of transforming into each other. It is interesting that Faraday expressed this idea even before the establishment of the law of conservation and transformation of energy. Faraday knew about Ampere's discovery, that he, figuratively speaking, converted electricity into magnetism. Reflecting on this discovery, Faraday came to the idea that if “electricity creates magnetism,” then vice versa, “magnetism must create electricity.” And back in 1823, he wrote in his diary: “Convert magnetism into electricity.” For eight years, Faraday worked to solve the problem. For a long time he was haunted by failures, and finally, in 1831, he solved it - he discovered the phenomenon of electromagnetic induction.

firstly, Faraday discovered the phenomenon of electromagnetic induction for the case when the coils are wound on the same drum. If an electric current appears or disappears in one coil as a result of connecting or disconnecting a galvanic battery from it, then a short-term current arises in the other coil at that moment. This current is detected by a galvanometer which is connected to the second coil.

Then Faraday also established the presence of an induced current in the coil when a coil in which an electric current flowed was brought closer to it or removed from it.

finally, the third case of electromagnetic induction that Faraday discovered was that a current appeared in the coil when a magnet was introduced or removed from it.

Faraday's discovery attracted the attention of many physicists, who also began to study the features of the phenomenon of electromagnetic induction. The next task was to establish the general law of electromagnetic induction. It was necessary to find out how and on what the strength of the induction current in a conductor depends or on what the value of the electromotive force of induction in a conductor in which an electric current is induced depends.

This task proved difficult. It was completely solved by Faraday and Maxwell later within the framework of the doctrine they developed about the electromagnetic field. But physicists also tried to solve it, adhering to the theory of long-range action in the study of electrical and magnetic phenomena, which was common at that time.

These scientists managed to do something. At the same time, they were helped by the rule discovered by St. Petersburg academician Emilius Christianovich Lenz (1804 - 1865) for finding the direction of the induction current in different cases of electromagnetic induction. Lenz formulated it as follows: “If a metal conductor moves in the vicinity of a galvanic current or magnet, then a galvanic current is excited in it in such a direction that if the conductor were stationary, the current could cause it to move in the opposite direction; it is assumed that a conductor at rest can only move in the direction of movement or in the opposite direction.”

This rule is very convenient for determining the direction of the induced current. We still use it now, only now it is formulated somewhat differently, with the burial of the concept of electromagnetic induction, which Lenz did not use.

But historically, the main significance of Lenz’s rule was that it gave rise to the idea of how to approach finding the law of electromagnetic induction. The fact is that the atom rule establishes a connection between electromagnetic induction and the phenomenon of interaction of currents. The question of the interaction of currents was already resolved by Ampere. Therefore, the establishment of this connection at first made it possible to determine the expression of the electromotive force of induction in a conductor for a number of special cases.

In general terms, the law of electromagnetic induction, as we said, was established by Faraday and Maxwell.

Electromagnetic induction is the phenomenon of the occurrence of electric current in a closed circuit when the magnetic flux passing through it changes.

Electromagnetic induction was discovered by Michael Faraday on August 29, 1831. He discovered that the electromotive force arising in a closed conducting circuit is proportional to the rate of change of the magnetic flux through the surface bounded by this circuit. The magnitude of the electromotive force (EMF) does not depend on what is causing the flux change - a change in the magnetic field itself or the movement of the circuit (or part of it) in the magnetic field. The electric current caused by this emf is called induced current.

Self-induction is the occurrence of induced emf in a closed conductive circuit when the current flowing through the circuit changes.

When the current in a circuit changes, the magnetic flux through the surface bounded by this circuit also changes proportionally. A change in this magnetic flux, due to the law of electromagnetic induction, leads to the excitation of an inductive emf in this circuit.

This phenomenon is called self-induction. (The concept is related to the concept of mutual induction, being, as it were, a special case of it).

The direction of the self-induction EMF always turns out to be such that when the current in the circuit increases, the self-induction EMF prevents this increase (directed against the current), and when the current decreases, it decreases (co-directed with the current). This property of self-induction emf is similar to the force of inertia.

The creation of the first relay was preceded by the invention in 1824 by the Englishman Sturgeon of an electromagnet - a device that converts the input electric current of a wire coil wound on an iron core into a magnetic field formed inside and outside this core. The magnetic field was recorded (detected) by its effect on the ferromagnetic material located near the core. This material was attracted to the core of the electromagnet.

Subsequently, the effect of converting the energy of electric current into mechanical energy of meaningful movement of external ferromagnetic material (anchor) formed the basis of various electromechanical devices for telecommunications (telegraphy and telephony), electrical engineering, and power engineering. One of the first such devices was an electromagnetic relay, invented by the American J. Henry in 1831.

The law of electromagnetic induction is a formula that explains the formation of EMF in a closed loop of a conductor when the magnetic field strength changes. The postulate explains the operation of transformers, chokes and other products that support the development of technology today.

The Michael Faraday Story

Michael Faraday was taken out of school along with his older brother due to a speech impediment. The discoverer of electromagnetic induction libbed, irritating the teacher. She gave money to buy a stick and flog a potential speech therapist client. And Michael’s older brother.

The future luminary of science was truly the darling of fate. Throughout his life, with due persistence, he found help. The brother returned the coin with contempt, reporting the incident to his mother. The family was not considered rich, and the father, a talented artisan, had difficulty making ends meet. The brothers began looking for work early: the family had been living on alms since 1801, Michael was in his tenth year at that time.

At the age of thirteen, Faraday entered a bookstore as a newspaper delivery boy. Through the whole city he barely makes it to addresses on opposite ends of London. Due to his diligence, the owner of Ribot gives Faraday a job as a bookbinder's apprentice for seven years free of charge. In ancient times, a man on the street paid a master for the process of acquiring a craft. Like George Ohm's skill as a mechanic, Faraday's bookbinding process was fully useful in the future. A big role was played by the fact that Michael scrupulously read the books that fell into his work.

Faraday writes that he equally readily believed Mrs. Marcet's treatise (Conversations on Chemistry) and the tales of the Thousand and One Nights. The desire to become a scientist played an important role in this matter. Faraday chooses two directions: electricity and chemistry. In the first case, the main source of knowledge is the Encyclopedia Britannica. An inquisitive mind requires confirmation of what is written, the young bookbinder constantly tests his knowledge in practice. Faraday becomes an experienced experimenter, which will play a leading role in the study of electromagnetic induction.

Let us remember that we are talking about a student without his own income. The elder brother and father provided assistance as best they could. From chemical reagents to assembling an electrostatic generator, experiments require an energy source. At the same time, Faraday manages to attend paid lectures on natural science and meticulously writes down his knowledge in a notebook. Then he binds the notes, using the acquired skills. The apprenticeship ends in 1812, Faraday begins to look for work. The new owner is not so accommodating, and, despite the prospect of becoming the heir to the business, Michael is on the way to the discovery of electromagnetic induction.

Faraday's scientific path

In 1813, fate smiled on the scientist who gave the world an idea of electromagnetic induction: he managed to get the position of secretary to Sir Humphrey Davy, a short period of acquaintance would play a role in the future. Faraday cannot bear to carry out the duties of a bookbinder any longer, so he writes a letter to Joseph Banks, then president of the Royal Scientific Society. A fact will tell you about the nature of the organization's activities: Faraday received a position called senior servant: he helps lecturers, wipes dust from equipment, and monitors transportation. Joseph Banks ignores the message, Michael does not lose heart and writes to Davy. After all, there are no other scientific organizations in England!

Davy is very attentive because he knows Michael personally. Not being naturally gifted with the ability to speak - remember his school experience - and express thoughts in writing, Faraday takes special lessons to develop the necessary skills. He carefully systematizes his experiences in a notebook and expresses his thoughts in a circle of friends and like-minded people. By the time he meets Sir Humphrey, Davy has achieved remarkable skill, and he petitions for the newly minted scientist to be accepted into the above-mentioned position. Faraday is happy, but initially there was an idea to appoint the future genius to wash dishes...

By the will of fate, Michael is forced to listen to lectures on various topics. Professors needed help only periodically; otherwise, they were allowed to be in the classroom and listen. Considering how much a Harvard education costs, this became a good leisure activity. After six months of brilliant work (October 1813), Davy invites Faraday on a trip to Europe, the war is over, you need to look around. This became a good school for the discoverer of electromagnetic induction.

Upon returning to England (1816), Faraday received the title of laboratory assistant and published his first work on the study of limestone.

Electromagnetism Research

The phenomenon of electromagnetic induction is the induction of an emf in a conductor under the influence of a changing magnetic field. Today, devices operate on this principle, from transformers to hobs. The championship in the field was given to Hans Oersted, who on April 21, 1820 noticed the effect of a closed circuit on a compass needle. Similar observations were published in the form of notes by Giovanni Domenico Romagnosi in 1802.

The merit of the Danish scientist is that he attracted many prominent scientists to the cause. So, it was noticed that the needle is deflected by a current-carrying conductor, and in the fall of that year the first galvanometer was born. The measuring device in the field of electricity has become a great help to many. Along the way, various points of view were expressed, in particular, Wollaston announced that it would be a good idea to make a current-carrying conductor rotate continuously under the influence of a magnet. In the 20s of the 19th century, euphoria reigned around this issue; before that, magnetism and electricity were considered independent phenomena.

In the fall of 1821, the idea was brought to life by Michael Faraday. It is said that then the first electric motor was born. On September 12, 1821, in a letter to Gaspard de la Rive, Faraday writes:

“I found out that the attraction and repulsion of a magnetic needle by a current-carrying wire is child’s play. A certain force will continuously rotate the magnet under the influence of electric current. I built theoretical calculations and managed to implement them in practice.”

The letter to de la Rive was not an accident. As he developed in the scientific field, Faraday gained many supporters and his only irreconcilable enemy... Sir Humphrey Davy. The experimental setup has been declared a plagiarism of Wollaston's idea. Approximate design:

The silver bowl is filled with mercury. Liquid metal has good electrical conductivity and serves as a moving contact.
At the bottom of the bowl there is a cake of wax, into which a bar magnet is inserted with one pole. The second rises above the surface of the mercury.
A wire connected to a source hangs from a height. Its end is immersed in mercury. The second wire is near the edge of the bowl.
If you pass a direct electric current through a closed circuit, the wire begins to describe circles around the mercury. The center of rotation becomes a permanent magnet.

The design is called the world's first electric motor. But the effect of electromagnetic induction has not yet manifested itself. There is an interaction between two fields, nothing more. Faraday, by the way, did not stop, and made a bowl where the wire is stationary, and the magnet moves (forming a surface of rotation - a cone). He proved that there is no fundamental difference between the field sources. That is why induction is called electromagnetic.

Faraday was immediately accused of plagiarism and hounded for several months, about which he wrote bitterly to trusted friends. In December 1821, a conversation took place with Wollaston; it seemed that the incident had been settled, but... a little later, a group of scientists resumed their attacks, and Sir Humphrey Davy became the head of the opposition. The essence of the main complaints was opposition to the idea of accepting Faraday as a member of the Royal Society. This weighed heavily on the future discoverer of the law of electromagnetic induction.

Discovery of the law of electromagnetic induction

For a time, Faraday seemed to abandon the idea of research in the field of electricity. Sir Humphrey Davy was the only one to throw the ball against Michael's candidacy. Perhaps the former student did not want to upset the patron, who was at that time the president of the society. But the thought of the unity of natural processes constantly tormented me: if electricity could be converted into magnetism, we must try to do the opposite.

This idea originated - according to some sources - in 1822, and Faraday constantly carried with him a piece of iron ore that resembled, serving as a “knot for memory”. Since 1825, being a full member of the Royal Society, Michael received the position of head of the laboratory and immediately made innovations. The staff now gathers once a week for lectures with visual demonstrations of the devices. Gradually, the entrance becomes open, even children get the opportunity to try new things. This tradition marked the beginning of the famous Friday evenings.

For five whole years Faraday worked on optical glass; the group did not achieve much success, but there were practical results. A key event occurred - the life of Humphrey Davy, who constantly opposed experiments with electricity, was cut short. Faraday rejected the offer of a new five-year contract and now began open research that led directly to magnetic induction. According to the literature, the series lasted 10 days, unevenly distributed between August 29 and November 4, 1831. Faraday describes his own laboratory setup:

Using soft (highly magnetic) 7/8" round iron, I made a ring with an outer radius of 3". In fact, it turned out to be a core. The three primary windings were separated from each other by cotton cloth and a tailor's cord so that they could be combined into one or used separately. The copper wire in each is 24 feet long. The quality of insulation is checked using batteries. The secondary winding consisted of two segments, each 60 feet long, separated from the primary by a distance.

From a source (presumably a Wollaston element), which consisted of 10 plates, each 4 square inches in area, power was supplied to the primary winding. The ends of the secondary were short-circuited with a piece of wire; a compass needle was placed along the circuit three feet from the ring. When the power source was closed, the magnetized needle immediately began to move, and after an interval returned to its original place. It is obvious that the primary winding causes a response in the secondary. Now we would say that the magnetic field propagates through the core and induces an EMF at the output of the transformer.