How to create a constant magnetic field. What is magnetic therapy? What does a magnetic field cure?

What are super strong magnetic fields?

In science, various interactions and fields are used as tools to understand nature. During a physical experiment, the researcher, influencing the object of study, studies the response to this influence. By analyzing it, they make a conclusion about the nature of the phenomenon. The most effective means of influence is a magnetic field, since magnetism is a widespread property of substances.

The strength characteristic of a magnetic field is magnetic induction. The following is a description of the most common methods for producing ultra-strong magnetic fields, i.e. magnetic fields with induction over 100 T (tesla).

For comparison -

• the minimum magnetic field recorded using a superconducting quantum interferometer (SQUID) is 10 -13 T;
• Earth's magnetic field – 0.05 mT;
• souvenir refrigerator magnets – 0.05 T;
• alnico (aluminum-nickel-cobalt) magnets (AlNiCo) – 0.15 T;
• ferrite permanent magnets (Fe 2 O 3) – 0.35 T;
• samarium-cobalt permanent magnets (SmCo) - 1.16 Tesla;
• the strongest neodymium permanent magnets (NdFeB) – 1.3 Tesla;
• electromagnets of the Large Hadron Collider - 8.3 Tesla;
• the strongest constant magnetic field (National High Magnetic Field Laboratory, University of Florida) - 36.2 Tesla;
• the strongest pulsed magnetic field achieved without destroying the installation (Los Alamos National Laboratory, March 22, 2012) is 100.75 Tesla.

Currently, research in the field of creating superstrong magnetic fields is being carried out in countries participating in the Megagauss Club and is discussed at International conferences on the generation of megagauss magnetic fields and related experiments ( gauss– unit of measurement of magnetic induction in the CGS system, 1 megagauss = 100 tesla).

To create magnetic fields of such strength, very high power is required, so at present they can only be obtained in a pulsed mode, and the pulse duration does not exceed tens of microseconds.

Discharge to a single-turn solenoid

The simplest method of obtaining ultra-strong pulsed magnetic fields with magnetic induction in the range of 100...400 Tesla is the discharge of capacitive energy storage devices onto single-turn solenoids ( solenoid- this is a single-layer cylindrical coil, the turns of which are wound closely, and the length is significantly greater than the diameter).

The internal diameter and length of the coils used usually do not exceed 1 cm. Their inductance is small (units of nanohenry), therefore, currents of megaampere level are required to generate super-strong fields in them. They are obtained using high-voltage (10-40 kilovolts) capacitor banks with low self-inductance and stored energy from tens to hundreds of kilojoules. In this case, the time for the induction to rise to the maximum value should not exceed 2 microseconds, otherwise the destruction of the solenoid will occur before a super-strong magnetic field is reached.

The deformation and destruction of the solenoid is explained by the fact that due to a sharp increase in the current in the solenoid, the surface (“skin”) effect plays a significant role - the current is concentrated in a thin layer on the surface of the solenoid and the current density can reach very large values. The consequence of this is the appearance in the solenoid material of an area with increased temperature and magnetic pressure. Already at an induction of 100 Tesla, the surface layer of the coil, made even of refractory metals, begins to melt, and the magnetic pressure exceeds the tensile strength of most known metals. With further growth of the field, the melting region spreads deep into the conductor, and evaporation of the material begins on its surface. As a result, explosive destruction of the solenoid material occurs (“skin layer explosion”).

If the value of magnetic induction exceeds 400 tesla, then such a magnetic field has an energy density comparable to the binding energy of an atom in solids and far exceeds the energy density of chemical explosives. In the zone of action of such a field, as a rule, complete destruction of the coil material occurs with a speed of expansion of the coil material of up to 1 kilometer per second.

Magnetic flux compression method (magnetic cumulation)

To obtain the maximum magnetic field (up to 2800 T) in the laboratory, the magnetic flux compression method is used ( magnetic cumulation).

Inside a conductive cylindrical shell ( liner) with radius r 0 and cross section S 0 an axial starting magnetic field with induction is created B 0 and magnetic flux F = B 0 S 0 And. Then the liner is symmetrically and quickly compressed by external forces, while its radius decreases to rf and cross-sectional area up to S f. The magnetic flux penetrating the liner also decreases in proportion to the cross-sectional area. A change in magnetic flux in accordance with the law of electromagnetic induction causes the appearance of an induced current in the liner, creating a magnetic field that tends to compensate for the decrease in magnetic flux. In this case, the magnetic induction increases accordingly to the value B f =B 0 *λ*S 0 /S f, where λ is the magnetic flux conservation coefficient.

The magnetic cumulation method is implemented in devices called magnetic-cumulative (explosive-magnetic) generators. The liner is compressed by the pressure of the explosion products of chemical explosives. The current source for creating the initial magnetic field is a capacitor bank. The founders of research in the field of creating magnetic-cumulative generators were Andrei Sakharov (USSR) and Clarence Fowler (USA).

In one of the experiments in 1964, a record field of 2500 Tesla was recorded using the MK-1 magnetic-cumulative generator in a cavity with a diameter of 4 mm. However, the instability of magnetic cumulation was the reason for the irreproducible nature of the explosive generation of superstrong magnetic fields. Stabilization of the magnetic cumulation process is possible by compressing the magnetic flux by a system of successively connected coaxial shells. Such devices are called cascade generators of ultra-strong magnetic fields. Their main advantage is that they provide stable operation and high reproducibility of ultra-strong magnetic fields. The multi-stage design of the MK-1 generator, using 140 kg of explosive, ensuring a compression speed of the liner of up to 6 km/s, made it possible to obtain a world record magnetic field of 2800 tesla in a volume of 2 cm 3 in 1998 at the Russian Federal Nuclear Center. The energy density of such a magnetic field is more than 100 times higher than the energy density of the most powerful chemical explosives.

Application of ultra-strong magnetic fields

The use of strong magnetic fields in physical research began with the works of the Soviet physicist Pyotr Leonidovich Kapitsa in the late 1920s. Ultra-strong magnetic fields are used in studies of galvanomagnetic, thermomagnetic, optical, magnetic-optical, and resonance phenomena.

They apply in particular:

What is a permanent magnet? A permanent magnet is a body that can maintain magnetization for a long time. As a result of repeated research and numerous experiments, we can say that only three substances on Earth can be permanent magnets (Fig. 1).

Rice. 1. Permanent magnets. ()

Only these three substances and their alloys can be permanent magnets, only they can be magnetized and maintain this state for a long time.

Permanent magnets have been used for a very long time, and first of all they are devices for orientation in space - the first compass was invented in China in order to navigate in the desert. Today, no one argues about magnetic needles or permanent magnets; they are used everywhere in telephones and radio transmitters and simply in various electrical products. They can be different: there are strip magnets (Fig. 2)

Rice. 2. Strip magnet ()

And there are magnets that are called arc-shaped or horseshoe-shaped (Fig. 3)

Rice. 3. Arc magnet ()

The study of permanent magnets is exclusively related to their interaction. A magnetic field can be created by an electric current and a permanent magnet, so the first thing that was done was research with magnetic needles. If we bring a magnet close to the arrow, we will see interaction - like poles will repel, and unlike poles will attract. This interaction is observed with all magnets.

Let's place small magnetic arrows along the strip magnet (Fig. 4), the south pole will interact with the north, and the north will attract the south. The magnetic needles will be located along the magnetic field line. It is generally accepted that magnetic lines are directed outside a permanent magnet from the north pole to the south, and inside the magnet from the south pole to the north. Thus, the magnetic lines are closed in exactly the same way as those of an electric current, these are concentric circles, they are closed inside the magnet itself. It turns out that outside the magnet the magnetic field is directed from north to south, and inside the magnet from south to north.

Rice. 4. Magnetic field lines of a strip magnet ()

In order to observe the shape of the magnetic field of a strip magnet, the shape of the magnetic field of an arc-shaped magnet, we will use the following devices or parts. Let's take a transparent plate, iron filings and conduct an experiment. Let's sprinkle iron filings on the plate located on the strip magnet (Fig. 5):

Rice. 5. Shape of the magnetic field of a strip magnet ()

We see that the magnetic field lines leave the north pole and enter the south pole; by the density of the lines we can judge the poles of the magnet; where the lines are thicker, the magnet poles are located there (Fig. 6).

Rice. 6. Shape of the magnetic field of an arc-shaped magnet ()

We will carry out a similar experiment with an arc-shaped magnet. We see that magnetic lines start at the north and end at the south pole throughout the magnet.

We already know that a magnetic field is formed only around magnets and electric currents. How can we determine the Earth's magnetic field? Any needle, any compass in the Earth's magnetic field is strictly oriented. Since the magnetic needle is strictly oriented in space, therefore, it is affected by a magnetic field, and this is the Earth’s magnetic field. We can conclude that our Earth is a large magnet (Fig. 7) and, accordingly, this magnet creates a fairly powerful magnetic field in space. When we look at the needle of a magnetic compass, we know that the red arrow points south and the blue arrow points north. How are the Earth's magnetic poles located? In this case, it is necessary to remember that the south magnetic pole is located at the north geographic pole of the Earth and the north magnetic pole of the Earth is located at the south geographic pole. If we consider the Earth as a body located in space, then we can say that when we go north along the compass, we will come to the south magnetic pole, and when we go south, we will end up at the north magnetic pole. At the equator, the compass needle will be located almost horizontally relative to the surface of the Earth, and the closer we are to the poles, the more vertical the needle will be. The Earth's magnetic field could change; there were times when the poles changed relative to each other, that is, the south was where the north was, and vice versa. According to scientists, this was a harbinger of great disasters on Earth. This has not been observed for the last few tens of millennia.

Rice. 7. Earth's magnetic field ()

Magnetic and geographic poles do not coincide. There is also a magnetic field inside the Earth itself, and, like in a permanent magnet, it is directed from the south magnetic pole to the north.

Where does the magnetic field in permanent magnets come from? The answer to this question was given by the French scientist Andre-Marie Ampère. He expressed the idea that the magnetic field of permanent magnets is explained by elementary, simplest currents flowing inside permanent magnets. These simplest elementary currents reinforce each other in a certain way and create a magnetic field. A negatively charged particle - an electron - moves around the nucleus of an atom; this movement can be considered directed, and, accordingly, a magnetic field is created around such a moving charge. Inside any body, the number of atoms and electrons is simply enormous; accordingly, all these elementary currents take an ordered direction, and we get a fairly significant magnetic field. We can say the same about the Earth, that is, the Earth's magnetic field is very similar to the magnetic field of a permanent magnet. A permanent magnet is a fairly bright characteristic of any manifestation of a magnetic field.

In addition to the existence of magnetic storms, there are also magnetic anomalies. They are associated with the solar magnetic field. When sufficiently powerful explosions or ejections occur on the Sun, they occur not without the help of the manifestation of the Sun's magnetic field. This echo reaches the Earth and affects its magnetic field, as a result we observe magnetic storms. Magnetic anomalies are associated with iron ore deposits in the Earth, huge deposits are magnetized by the Earth’s magnetic field for a long time, and all bodies around will experience the magnetic field from this anomaly, compass arrows will show the wrong direction.

In the next lesson we will look at other phenomena associated with magnetic actions.

Bibliography

1. Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. Physics 8 / Ed. Orlova V.A., Roizena I.I. - M.: Mnemosyne.
2. Peryshkin A.V. Physics 8. - M.: Bustard, 2010.
3. Fadeeva A.A., Zasov A.V., Kiselev D.F. Physics 8. - M.: Enlightenment.

1. Class-fizika.narod.ru ().
2. Class-fizika.narod.ru ().
3. Files.school-collection.edu.ru ().

Homework

1. Which end of the compass needle is attracted to the Earth's north pole?
2. In what place on Earth can you not trust the magnetic needle?
3. What does the density of lines on a magnet indicate?

Introduction 1

(1) The most obvious mechanical phenomenon in electrical and magnetic experiments is the interaction, due to which bodies in certain states set each other in motion, despite the presence of a fairly significant distance between them.

Therefore, for a scientific interpretation of these phenomena, it is first of all necessary to establish the magnitude and direction of the force acting between the bodies, and if it is found that this force to some extent depends on the relative position of the bodies and on their electrical or magnetic state, then at first glance it seems natural to explain these facts by supposing the existence of something else, at rest or in motion in every body, constituting its electric or magnetic state, and capable of acting at a distance in accordance with mathematical laws.

In this way, mathematical theories of static electricity, magnetism, mechanical action between conductors carrying currents, and the theory of current induction arose. In these theories, the force acting between two bodies is considered only as depending on the state of the bodies and their relative position, the environment is not taken into account.

These theories more or less explicitly admit the existence of substances whose particles have the ability to act on each other at a distance. The most complete development of a theory of this kind belongs to W. Weber, 2 who included in it both electrostatic and electromagnetic phenomena.

Having done this, however, he was forced to admit that the force acting between two electric particles depends not only on their mutual distance, but also on their relative speed.

This theory as developed by Weber and Neumann 3 is extremely ingenious and surprisingly comprehensive in its application to the phenomena of static electricity, electromagnetic attractions, induction of currents and diamagnetic phenomena; this theory is all the more authoritative for us because it was the guiding idea of ​​the one who made such great strides in the practical part of the science of electricity, both by introducing a constant system of units into electrical measurements, and by actually determining electrical quantities with a hitherto unknown accuracy 4 .

(2) However, the mechanical difficulties associated with the assumption of the existence of particles acting at a distance with forces depending on their velocities are such that they prevent me from considering this theory as definitive, although it is possible that it may still be useful in relation to establishing coordination between phenomena. Therefore, I preferred to look for explanations of the facts in a different direction, assuming that they are the result of processes that occur both in the environment surrounding the body and in the excited bodies themselves, and trying to explain the interactions between bodies distant from each other without assuming the existence of forces that can directly operate at noticeable distances.

(3) The theory which I propose may be called the electromagnetic field theory, because it deals with the space surrounding electric or magnetic bodies, and it may also be called the dynamic theory, since it admits that there is matter in this space , which is in motion, through which the observed electromagnetic phenomena are produced.

(4) The electromagnetic field is that part of space that contains and surrounds bodies that are in an electric or magnetic state. This space can be filled with any kind of matter, or we can try to remove all dense matter from it, as is the case in Heusler tubes 5 or in other so-called vacuum tubes. However, there is always a sufficient amount of matter to perceive and transmit wave movements of light and heat. And since the transmission of radiations does not change very much, if the so-called vacuum is replaced by transparent bodies of appreciable density, we are forced to admit that these wave movements relate to ethereal substance, and not to dense matter, the presence of which only in some measure changes movement of the ether. We therefore have some reason to assume, based on the phenomena of light and heat, that there is some kind of ethereal medium that fills space and permeates all bodies, which has the ability to be set in motion, to transmit this movement from one part of itself to another and to communicate this movement dense matter, heating it and influencing it in a variety of ways.

(5) The energy imparted to the body by heating must have previously existed in the moving medium, for the wave movements left the source of heat some time before they reached the heated body itself, and during this time the energy must have existed half in the form of motion of the medium and half in the form of elastic tension. Based on these considerations, Professor W. Thomson 6 argued that this medium should have a density comparable to the density of ordinary matter, and even determined the lower limit of this density.

(6) Therefore, we can, as a given, derived from the branch of science, regardless of the one with which we (in the case under consideration) are dealing, accept the existence of a penetrating medium with a small but real density, with the ability to be set in motion and transmit motion from one part to another with great, but not infinite speed.

Consequently, the parts of this medium must be so connected that the movement of one part depends in some way on the movement of the remaining parts, and at the same time these connections must be capable of a certain kind of elastic displacement, since the communication of movement is not instantaneous, but requires time.

Therefore, this medium has the ability to receive and store two types of energy, namely “actual” energy, depending on the movement of its parts, and “potential” energy, which is the work that the medium will perform due to its elasticity, returning to its original state, after that the displacement she experienced.

The propagation of oscillations consists of the continuous conversion of one of these forms of energy into the other alternately, and at any instant the amount of energy in the whole medium is equally divided, so that half the energy is the energy of motion and the other half the energy of elastic tension.

(7) A medium having this kind of structure may be capable of other types of movement and displacement than those that determine the phenomena of light and heat; some of them may be such that they are perceived by our senses through the phenomena which they produce.

(8) Now we know that a luminiferous medium in some cases experiences the action of magnetism, since Faraday 7 discovered that in those cases when a plane polarized beam passes through a transparent diamagnetic medium in the direction of magnetic lines of force formed by magnets or currents, then the plane polarization begins to rotate.

This rotation always occurs in the direction in which positive electricity must flow around the diamagnetic body in order to form an effective magnetic field.

Verde 8 has since discovered that if a diamagnetic body is replaced by a paramagnetic one, for example, a solution of ferric chloride in ether, then the rotation occurs in the opposite direction.

Professor W. Thomson 9 Tuck pointed out that no distribution of forces acting between the parts of any medium, the only movement of which is the movement of light vibrations, is sufficient to explain these phenomena, but that we must admit the existence in the medium of a movement depending on magnetization, in addition to that vibratory motion which is light.

It is absolutely correct that rotation of the plane of polarization due to magnetic influence was observed only in media with a noticeable density. But the properties of the magnetic field do not change so much when one medium is replaced by another or by a vacuum to allow us to assume that a dense medium does more than simply change the motion of the ether. We therefore have a legitimate basis to pose the question: does not the movement of the ethereal medium take place wherever magnetic effects are observed? We have some reason to assume that this movement is a rotational movement, having its axis in the direction of the magnetic force.

(9) We can now discuss another phenomenon observed in the electromagnetic field. When a body moves across lines of magnetic force, it experiences what is called electromotive force; the two opposite ends of the body are electrified in opposite ways, and the electric current tends to pass through the body. When the electromotive force is large enough and acts on certain chemically complex bodies, it decomposes them and causes one of the components to be directed towards one end of the body, and the other in the exact opposite direction 10.

In this case we have an obvious manifestation of a force causing an electric current in spite of resistance, and electrifying the ends of the body in the opposite manner; this peculiar state of the body is maintained only by the action of an electromotive force, and as soon as this force is removed, it tends, with an equal and opposite force, to cause a reverse current through the body and restore its original electrical state. Finally, if this force is strong enough, it decomposes the chemical compounds and moves the components in two opposite directions, while their natural tendency is to interconnect with such a force as can generate an electromotive force in the opposite direction.

This force is therefore a force acting on a body due to its motion through an electromagnetic field or due to changes occurring in that field itself; the action of this force is manifested either in the generation of current and heating of the body, or in the decomposition of the body, or, if it cannot do either one or the other, then in bringing the body into a state of electric polarization - a forced state, in which the ends of the body are electrified in the opposite way and from which the body tends to free itself as soon as the disturbing force is removed.

(10) According to the theory I propose, this “electromotive force” is the force that arises when motion is transmitted from one part of the medium to another, so that it is thanks to this force that the movement of one part causes the movement of another. When an electromotive force acts along a conducting path, it produces a current, which, if it meets resistance, causes the electrical energy to be continually converted into heat; the latter can no longer be restored in the form of electrical energy by any reversal of the process.

(11) But when an electromotive force acts on a dielectric, it creates a state of polarization of its parts, which is analogous to the polarization of the parts of a mass of iron under the influence; magnet and which, like magnetic polarization, can be described as a state in which each particle has opposite ends in opposite states 11 .

In a dielectric under the influence of an electromotive force, we can imagine that the electricity in each molecule is so displaced that one side of the molecule becomes positively electrified and the other negatively electrified, but the electricity remains completely associated with the molecule and does not pass from one molecule to the other. another.1 The effect of this action on the entire mass of the dielectric is expressed! in the general displacement of electricity in a certain direction. 12 This displacement is not equivalent to a current, because when it reaches a certain degree it remains unchanged, but it is the beginning of a current, and its changes produce currents in positive or negative directions according to whether the displacement increases or decreases 12. There are no signs of any electrification inside the dielectric, since the electrification of the surface of any molecule is neutralized by the opposite electrification of the surface of the molecule in contact with it; but on the boundary surface of the dielectric, where electrification is not neutralized, we find phenomena indicating positive or negative electrification of this surface. The relationship between electromotive force and the amount of electrical displacement it produces depends on the nature of the dielectric, the same electromotive force generally producing greater electrical displacement in solid dielectrics, such as glass or sulfur, than in air.

(12) Here, therefore, we see another effect of the electromotive force, namely electrical displacement, which, according to our theory, is a kind of elastic compliance to the action of a force, similar to that which occurs in structures and machines due to imperfect rigidity of connections 13 .

(13) The practical study of the inductive capacitance of dielectrics 14 is made difficult due to two interfering phenomena. The first is the conductivity of the dielectric, which, although in many cases extremely small, is nevertheless not completely imperceptible. The second is a phenomenon called electrical absorption 15 and consists in the fact that when a dielectric is exposed to an electromotive force, the electrical displacement gradually increases, and if the electromotive force is removed, the dielectric does not instantly return to its original state, but discharges only part of the electrification imparted to it and , being left to its own devices, gradually acquires electrification on its surface, while the interior of the dielectric gradually becomes depolarized. Almost all solid dielectrics exhibit this phenomenon, which explains the residual charge of the Leyden jar and some phenomena in electrical cables described by F. Jenkin 16 .

(14) We encounter here two other types of compliance, different from the elasticity of an ideal dielectric, which we compared with an ideally elastic body. Compliance, which relates to conductivity, can be compared with the compliance of a viscous fluid (in other words, a fluid having high internal friction) or a soft body, in which the slightest force produces a constant change in shape, increasing with the time of action of the force. The compliance associated with the phenomenon of electrical absorption can be compared with the compliance of the elastic body of a cellular structure containing a thick liquid in its cavities. Such a body, being subjected to pressure, compresses gradually, and when the pressure is removed, the body does not immediately return to its previous shape, because the elasticity of the matter of the body must gradually overcome the viscosity of the liquid before complete equilibrium is restored. Some solids, although not having the structure of which we spoke above, exhibit mechanical properties of this kind, 17 and it is quite possible that these same substances, as dielectrics, have similar electrical properties, and if they are magnetic substances, they have corresponding properties relating to the acquisition, retention and loss of magnetic polarity 18.

(15) Therefore it seems that certain phenomena of electricity and magnetism lead to the same conclusions as optical phenomena, namely, that there is an ethereal medium permeating all bodies and being modified only in some degree by their presence; that parts of this medium have the power of being moved by electric currents and magnets; that this movement is communicated from one part of the medium to another with the help of forces arising from the connections of these parts; that under the influence of these forces a certain displacement arises, depending on the elasticity of these connections, and that, as a result, energy in the medium can exist in two different forms, one of which is the actual energy of movement of parts of the medium, and the other is potential energy due to the connections of the parts due to their elasticity.

(16) Hence we arrive at the concept of a complex mechanism, capable of a vast variety of movements, but at the same time connected in such a way that the movement of one part depends, according to certain relations, on the movement of other parts, and these movements are communicated by forces arising from the relative displacement of interconnected parts due to elasticity of connections. Such a mechanism must obey the general laws of dynamics, and we must be able to deduce all the consequences of this motion, supposing that the form of the relation between the movements of the parts is known. (17) We know that when an electric current flows in a conducting circuit, the adjacent part of the field is characterized by known magnetic properties, and if there are two circuits in the field, the magnetic properties of the field relating to both currents are combined. Thus, each part of the field is in connection with both currents, and both currents are connected with each other by virtue of their connection with the magnetization of the field. The first result of this connection, which I propose to study, is the induction of one current by another and the induction due to the movement of conductors in a field.

Another result that follows from this is the mechanical interaction between the conductors through which currents flow. The phenomenon of current induction was derived from the mechanical interaction of conductors by Helmholtz 19 and Thomson 20. I followed the reverse order and derived mechanical interaction from the laws of induction. I then described experimental methods for determining the values ​​of L, M, N 21 on which these phenomena depend.

(18) I then apply the phenomena of induction and attraction of currents to the study of the electromagnetic field and to the establishment of a system of magnetic lines of force indicating their magnetic properties. By examining the same field with a magnet, I show the distribution of its equipotential magnetic surfaces intersecting the field lines at right angles.

To introduce these results into the realm of symbolic calculus, 22 I express them in the form of general electromagnetic field equations.

These equations express:
(A) Relationship between electrical displacement, true conduction current, and total current composed of both.
(B) The relationship between the magnetic lines of force and the induction coefficients of the circuit, as already derived from the laws of induction.
(C) The relationship between the strength of a current and its magnetic effects according to the electromagnetic system of units.
(D) The value of the electromotive force in any body arising from the movement of the body in a field, changes in the field itself, and changes in electric potential from one part of the field to another.
(E) The relationship between electrical displacement and the electromotive force that produces it.
(F) The relationship between electric current and the electromotive force that conducts it.
(G) The relationship between the amount of free electricity at any point and the electrical displacements in its vicinity.
(H) The relationship between the increase or decrease in free electricity and nearby electric currents. There are 20 such equations in total, containing 20 variables.

(19) I then express through these quantities the internal energy of the electromagnetic field as depending partly on the magnetic and partly on the electric polarization at each point 23 .

From here I determine the acting mechanical force, firstly, on a movable conductor through which an electric current flows; secondly, to the magnetic pole; thirdly, on an electrified body.

The latter result, namely the mechanical force acting on an electrified body, gives rise to an independent method of electrical measurement based on electrical actions. The ratio between the units used in these two methods appears to depend on what I have called the "electrical elasticity" of the medium, and is the rate which was determined experimentally by Weber and Kohlrausch.

I then show how to calculate the electrostatic capacitance of a capacitor and the specific inductive capacitance of a dielectric.

The case of a capacitor consisting of parallel layers of substances having different electrical resistances and inductive capacitances is studied further and it is shown that the phenomenon called electrical absorption, generally speaking, will take place, i.e. if the capacitor is suddenly discharged, then after a short time it will detect the presence residual charge.

(20) The general equations are further applied to the case of a magnetic disturbance propagating through a non-conducting field, and it is shown that the only disturbances that can propagate in this way are disturbances transverse to the direction of propagation, and that the speed of propagation is the speed v, determined experimentally from experiments similar to Weber's, which expresses the number of electrostatic units of electricity contained in one electromagnetic unit.

This speed is so close to the speed of light that we seem to have good reason to conclude that light itself (including radiant heat and other radiations) is an electromagnetic disturbance in the form of waves propagating through an electromagnetic field according to the laws of electromagnetism 24 . If this is so, then the coincidence between the elasticity of the medium, calculated, on the one hand, from fast light vibrations and, on the other hand, found by the slow process of electrical experiments, shows how perfect and correct the elastic properties of the medium must be if it is not filled with any -or matter denser than air. If the same character of elasticity is preserved in dense transparent bodies, then it turns out that the square of the refractive index is equal to the product of the specific dielectric capacitance and the specific magnetic capacitance 25 . Conducting media quickly absorb such radiation and are therefore usually opaque.

The concept of the propagation of transverse magnetic disturbances to the exclusion of longitudinal ones is definitely pursued by Professor Faraday 26 in his “Thoughts on Ray Vibrations.” The electromagnetic theory of light as proposed by him is the same in essence as that which I am developing in this report, except that in 1846 there was no data for calculating the speed of propagation 27 .

(21) The general equations are then applied to the calculation of the mutual induction coefficients of the two circular currents and the self-inductance coefficient of the coil.

The absence of a uniform distribution of current in different parts of the wire cross-section at the moment the current begins to flow, as I believe, is being studied for the first time, and a corresponding correction for the self-induction coefficient has been found.

These results are applied to the calculation of the self-inductance of the coil used in the experiments of the British Electrical Resistance Standards Association Committee, and the values ​​obtained are compared with those determined experimentally.

* In the book: D. K. Maxwell Selected works on the theory of the electromagnetic field. M, 1954, p. 251-264.
1 Royal Society Transactions, vol. CLV, 1864
2 Wilhelm Weber (1804-1891) - German physicist, derived the elementary law of long-range electrodynamics; together with Kohlrausch Rudolf (1809-1858), he first measured in 1856 the ratio of electrostatic and magnetic units of charge, which turned out to be equal to the speed of light (3-108 m/s).
3 Electrodynamische Maassbestimmungen, Leipzig. Trans, vol. 1, 1849 and Taylor's Scientific Memoirs, vol. V, chapter XIV. “Explicare tentatur quomodo fiat ut lucis planum polarizationis per vires electricas vel magneticas declinetur”, Halis Saxonum, 1858.
4 This refers to the experiments of Weber and Kohlrausch.
5 Heinrich Geisler (1814-1879) was a German physicist who designed a number of physical instruments: hydrometers, mercury pumps, vacuum tubes - the so-called Heusler tubes, etc.
6 Thomson William (Lord Kelvin) (1824-1907) - an outstanding English physicist, one of the founders of thermodynamics; introduced the absolute temperature scale that bears his name, developed the theory of electrical oscillations, obtaining the formula for the period of an oscillatory circuit, the author of many other discoveries and inventions, and a supporter of the mechanistic picture of the physical world. W. Thomson. "On the Possible Density of the Lumminiterous Medium and on the Mechanical Value of a Cubis Mile of Sunlight", Transactions of the Royal Society of Edinburgh, p. 57, 1854.
7 This is what Maxwell calls kinetic energy.
8 "Exp. Res.", series XIX. Emile Verdet (1824-1866) - French physicist who experimentally discovered that the magnetic rotation of the plane of polarization is proportional to the square of the wavelength of light. Verdet, Comptes rendus, 1856, second half, with 529 and 1857, first half, p. 1209.
9 So W. Thomson, Proceedings of the Royal Society, June 1856 and June 1861.
10 Maxwell adheres to outdated ideas about the decomposition of electrolytes by an electric field.
11 Faraday, “Exp. Res", series XI; Mossotti, Mem. della Soc. Italina (Mode-pa), vol. XXIV, part 2, p. 49.
12 Here Maxwell introduces the concept of displacement current.
13 Elasticity theory models are used for illustrative purposes.
14 This is what Maxwell calls the dielectric constant of a substance.
15 Faraday, "Exp Res" (1233-1250).
16 F. Jenkm Reports of the British Association, 1859, p. 248, and Report of the Committee of the Board of Trade on Submarine Cables, p. 136 and 464.
17 As, for example, a composition of glue, molasses, etc., from which small plastic figures are made, which, being deformed, only gradually acquire their original shape.
18 Another example of how Maxwell uses analogies from the theory of elasticity.
19 Russian edition, Helmholtz. "On maintaining strength." M., 1922.
20 W. Thomson. Reports of the British Association, 1848; Phil. Mag., December 1851.
21 L, M, N are some geometric quantities introduced by Maxwell to describe the dependence of the interaction of conductors with current: L depends on the shape of the first conductor, N on the shape of the second, and M on the relative position of these conductors.
22 This "symbolic calculus" is borrowed from Hamilton's work on vector and operator analysis.
23 These equations in their modern form (in SI) look like this: (A) is not an equation, but a definition of the total current density vector:
24 Here Maxwell emphasizes the electromagnetic nature of light.
25 That is, p2 = e|l.
26 Phil. Mag., May 1846 or “Exp. Res.", vol. III.
27 The first reliable values ​​for the speed of light were obtained in the experiments of I. Fizeau (1849) and L. Foucault (1850).

Examples of sources of single electromagnetic pulses: nuclear explosion, lightning discharge, electrical discharge, switching in electrical circuits. The EMR spectrum is most often pink. Examples of sources of multiple electromagnetic pulses: collector machines, corona discharge on alternating current, intermittent arc discharge on alternating current.

In technology, electromagnetic radiation with a limited spectrum is most often encountered, but it, like EMR from a nuclear explosion, can lead to equipment failure or the creation of powerful interference. For example, radiation from radar stations, electrical erosion installations, digital communications, etc.

Electromagnetic field and its effect on human health

1. What is EMF, its types and classification

2. Main sources of EMF

2.1 Electric transport

2.2 Power lines

2.3 Electrical wiring

2.7 Cellular

2.8 Radars

2.9 Personal computers

3. How does EMF affect health?

4. How to protect yourself from EMF

In practice, when characterizing the electromagnetic environment, the terms “electric field”, “magnetic field”, “electromagnetic field” are used. Let us briefly explain what this means and what connection exists between them.

An electric field is created by charges. For example, in all the well-known school experiments on the electrification of ebonite, an electric field is present.

A magnetic field is created when electric charges move through a conductor.

To characterize the magnitude of the electric field, the concept of electric field strength is used, symbol E, unit of measurement V/m. The magnitude of the magnetic field is characterized by the magnetic field strength H, unit A/m. When measuring ultra-low and extremely low frequencies, the concept of magnetic induction B is also often used, unit T, one millionth of a T corresponds to 1.25 A/m.

By definition, an electromagnetic field is a special form of matter through which interaction occurs between electrically charged particles. The physical reasons for the existence of an electromagnetic field are related to the fact that a time-varying electric field E generates a magnetic field H, and a changing H generates a vortex electric field: both components E and H, continuously changing, excite each other. The EMF of stationary or uniformly moving charged particles is inextricably linked with these particles. With the accelerated movement of charged particles, the EMF “breaks away” from them and exists independently in the form of electromagnetic waves, without disappearing when the source is removed.

Electromagnetic waves are characterized by wavelength, symbol - l. A source that generates radiation, and essentially creates electromagnetic oscillations, is characterized by frequency, designated f.

An important feature of EMF is its division into the so-called “near” and “far” zones. In the “near” zone, or induction zone, at a distance from the source r 3l. In the “far” zone, the field intensity decreases in inverse proportion to the distance to the source r -1.

In the “far” zone of radiation there is a connection between E and H: E = 377H, where 377 is the wave impedance of the vacuum, Ohm. Therefore, as a rule, only E is measured. In Russia, at frequencies above 300 MHz, the electromagnetic energy flux density, or Poynting vector, is usually measured. Denoted as S, the unit of measurement is W/m2. PES characterizes the amount of energy transferred by an electromagnetic wave per unit time through a unit surface perpendicular to the direction of propagation of the wave.

International classification of electromagnetic waves by frequency

Frequency range name

1. Vadim described more than 4 years ago a practical example of the convergence of ring-shaped waves on a primitive-to-understand method of throwing a lifebuoy onto the water. The waves diverged from the source and actually converged. There were theoretically unsubstantiated attempts to create an electromagnetic shell of a fictitious “tempo machine”. Frankly, he has far-sighted grains, intuitive, not yet understood.

3. No matter how paradoxical it may seem, turning back time is possible. but with a further changed course.

4.The speed of time is not the same.

5. RELATIVITY - space and time for a given world and humanity - a measure of the speed of light, then another world. different speeds, different laws. Also in reduction.

6. "Big Bang" about 14 billion light years, just a few moments in another world, in another flow, time, which for humanity is 5 minutes - for other worlds - billions of years.

7. The infinite universe for OTHERS is like an invisible quantum particle and vice versa.

The introduction of new technologies and the widespread use of electricity has led to the emergence of artificial electromagnetic fields, which most often have a harmful effect on humans and the environment. These physical fields arise where there are moving charges.

The nature of the electromagnetic field

The electromagnetic field is a special type of matter. It occurs around conductors along which electric charges move. Such a force field consists of two independent fields - magnetic and electric, which cannot exist in isolation from one another. When an electric field arises and changes, it invariably generates a magnetic field.

One of the first to study the nature of alternating fields in the middle of the 19th century was James Maxwell, who is credited with creating the theory of the electromagnetic field. The scientist showed that electric charges moving with acceleration create an electric field. Changing it generates a field of magnetic forces.

The source of an alternating magnetic field can be a magnet if it is set in motion, as well as an electric charge that oscillates or moves with acceleration. If a charge moves at a constant speed, then a constant current flows through the conductor, which is characterized by a constant magnetic field. Propagating in space, the electromagnetic field transfers energy, which depends on the magnitude of the current in the conductor and the frequency of the emitted waves.

Impact of electromagnetic field on humans

The level of all electromagnetic radiation created by man-made technical systems is many times higher than the natural radiation of the planet. This field is characterized by a thermal effect, which can lead to overheating of body tissues and irreversible consequences. For example, prolonged use of a mobile phone, which is a source of radiation, can lead to an increase in the temperature of the brain and the lens of the eye.

Electromagnetic fields generated when using household appliances can cause the appearance of malignant tumors. This especially applies to children's bodies. A person's prolonged presence near a source of electromagnetic waves reduces the efficiency of the immune system and leads to heart and vascular diseases.

Of course, it is impossible to completely abandon the use of technical means that are a source of electromagnetic fields. But you can use the simplest preventive measures, for example, use a cell phone only with a headset, and do not leave device cords in electrical outlets after using equipment. In everyday life, it is recommended to use extension cords and cables that have protective shielding.

if a field is needed to magnetize something, then this piece of material to be magnetized must be included in the magnetic circuit. those. We take a closed steel core, make an opening in it as long as the material that we need to magnetize, insert this material into the resulting opening, so we close the sawn magnetic circuit again. the field penetrating your material will be very homogeneous.

How to create an electromagnetic field

An electromagnetic field does not arise on its own; it is emitted by some device or object. Before assembling such a device, it is necessary to understand the very principle of the appearance of the field. From the name it is easy to understand that this is a combination of magnetic and electronic fields that can generate each other under certain conditions. The concept of EMF is associated with the name of the scientist Maxwell.

Researchers from the Laboratory of High Magnetic Fields in Dresden have set a new world record by creating the strongest magnetic field produced artificially. Using a two-layer inductor coil weighing 200 kilograms and dimensions comparable to the size of an ordinary bucket, they were able to obtain a magnetic field of 91.4 tesla within a few tens of milliseconds. As a reference, the previous record in this area was 89 Tesla, which stood for many years, which was set by researchers from the Los Alamos National Laboratory, USA.

91 Tesla is an incredibly powerful magnetic field; conventional high-power electromagnets used in industrial and household appliances produce a magnetic field not exceeding 25 Tesla. Obtaining magnetic fields of prohibitive values ​​requires special approaches; such electromagnets are manufactured in a special way so that they can ensure the unhindered passage of a large amount of energy and remain safe and sound. It is known that electric current flowing through an inductor produces a magnetic field, but this magnetic field interacts with the electrons in the conductor, repelling them in the opposite direction, i.e. creates electrical resistance. The greater the magnetic field produced by the electromagnet, the greater the repulsive effect on the electrons that occurs in the coil conductors. And when a certain limit is reached, this impact can lead to complete destruction of the electromagnet.

In order to prevent the coil from self-destructing under the influence of its own magnetic field, German scientists “dressed” the coil turns in a “corset” of flexible and durable material, similar to that used in body armor. This solution gave scientists a coil capable of generating a magnetic field of 50 Tesla for two hundredths of a second without destruction. Their next step was quite predictable: to the first coil they added another coil of 12 layers, also enclosed in a “corset” of fiber. The second coil is capable of withstanding a magnetic field of 40 tesla, but the total magnetic field from the two coils, obtained with the help of some tricks, exceeded the threshold of 90 tesla.

But people still need very strong magnets. More powerful, precisely shaped magnetic fields make it possible to better study and measure some of the properties of new materials that scientists are constantly inventing and creating. Therefore, this new powerful electromagnet was appreciated by some scientists in the field of materials science. HZDR researchers have already received orders for six of these electromagnets, which they are expected to produce over the next few years.

Sources: engangs.ru, it-med.ru, tinyfamily.ru, www.kakprosto.ru, flyback.org.ru, dokak.ru, www.dailytechinfo.org