The use of magnets in different fields of activity of modern society. What are the magnets for

There are magnets of two different species. Some are so-called permanent magnets made from "magnetic solid" materials. Them magnetic properties Not related to the use of external sources or currents. The other type includes so-called electromagnets with a core from "magnetically soft" iron. Magnetic fields created by them are mainly due to the fact that an electric current passes through the wire covering the core.

Magnetic poles and magnetic field.

The magnetic properties of the rod magnet are most noticeable near the ends. If such a magnet is suspended for the middle part so that it can be freely rotated in the horizontal plane, then it will occupy the position approximately corresponding to the direction from the north to the south. The end of the rod, pointing to the north, is called the North Pole, and the opposite end - the southern pole. The varieve poles of two magnets are attracted to each other, and the same names are repelled.

If you bring the low-income iron bar to one of the magnet poles, then the latter will temporarily magnetize. At the same time, the pole of the magnetized bar of the magnet of the magnetic bar will be opposite to the name, and the distant - the same name. Attraction between the magnet pole and the opposite pole induced in Bruke and the magnet action is explained. Some materials (for example, steel) themselves become weak permanent magnets after they are near a permanent magnet or an electromagnet. The steel rod can be magnetized, simply by spending on its end the end of the core permanent magnet.

So, the magnet attracts other magnets and objects from magnetic materials without being in contact with them. Such an action is explained by the existence in the space around the magnetic field magnet. Some idea of \u200b\u200bthe intensity and direction of this magnetic field can be obtained by pouring on a sheet of cardboard or glass, laid on a magnet, iron sawdust. The sawmills are lined up with chains in the direction of the field, and the lines of lines from the sawdust will correspond to the intensity of this field. (The curves of the whole magnet, where the magnetic field intensity is the highest.)

M. Faraday (1791-1867) introduced for magnets the concept of closed induction lines. Induction lines go into the surrounding space from a magnet at its north pole, enter the magnet in the southern pole and pass inside the magnet material from the southern pole back to the northern, forming a closed loop. The total number of induction lines emerging from the magnet is called a magnetic flux. Magnetic flux density, or magnetic induction ( IN) is equal to the number of induction lines passing by normal through the elementary platform of a single magnitude.

The magnetic induction is determined by the force with which the magnetic field acts on the conductor in it in it. If the conductor for which the current passes I., Located perpendicular to induction lines, then by the AMPER's law F.acting on the conductor perpendicular to the field, and the conductor and proportional to the magnetic induction, the strength of the current and the length of the conductor. Thus, for magnetic induction B. You can write an expression

where F. - power in Newton, I. - Current in amperes, l. - Length in meters. The unit of measurement of magnetic induction is Tesla (TL).

Galvanometer.

A galvanometer is a sensitive device for measuring weak currents. The galvanometer uses the torque arising in the interaction of a horseshoe-shaped permanent magnet with a small cunning coil (weak electromagnet) suspended in the gap between the poles of the magnet. The torque, and consequently, the deviation of the coil is proportional to the current and complete magnetic induction in the air gap, so that the scale of the device with small deviations of the coil is almost linear.

Magnetizing force and magnetic field strength.

Next, you should enter another value that characterizes the magnetic effect of the electric current. Suppose that the current passes through the wire of the long coil, inside which is located magnetized material. The magnetizing force is called the product of the electric current in the coil on the number of its turns (this force is measured in amperes, since the number of turns is the value of dimensionless). Magnetic field tension N. It is equal to the magnetizing force per unit of the length of the coil. Thus, the value N. Measured in amperes per meter; It determines the magnetization acquired by the material inside the coil.

In vacuum magnetic induction B. proportional to the tension of the magnetic field N.:

where m.0 - so-called Magnetic constant having a universal value 4 p.H 10 -7 Gn / m. In many materials a magnitude B. Approximately proportional N.. However, in ferromagnetic materials, the ratio between B. and N. more complicated (what will be said below).

In fig. 1 shows a simple electromagnet designed to capture cargo. The source of energy serves accumulator battery direct current. The figure also shows the power lines of the electromagnet field, which can be revealed by the usual method of iron sawdust.

Large electromagnets with iron cores and a very large number of ampere-turns operating in continuous mode, have a large magnetizing force. They create a magnetic induction of up to 6 T. in the interval between the poles; This induction is limited only by mechanical stresses, heating coils and magnetic saturation of the core. A row of giant electromagnets (without a core) with water-cooled, as well as installations for the creation of pulsed magnetic fields, was constructed by P.L. Kapitsa (1894-1984) in Cambridge and at the Institute of Physical Problems of the Academy of Sciences of the USSR and F.Bitter (1902-1967) Massachusetts Technology Institute. On such magnets managed to reach induction to 50 tle. A relatively small electromagnet, which creates fields up to 6.2 T., which consumes the electrical power of 15 kW and cooled by liquid hydrogen, was developed in the Losalamamos National Laboratory. Such fields are obtained at cryogenic temperatures.

Magnetic permeability and its role in magnetism.

Magnetic permeability m. - This is a value that characterizes the magnetic properties of the material. Ferromagnetic metals Fe, Ni, CO and their alloys have very high maximum permeability - from 5000 (for Fe) to 800,000 (for supermalloa). In such materials with relatively small field strengths H. Large induction arise B.But the connection between these values, generally speaking, is nonlinear due to the phenomena of saturation and hysteresis, which is mentioned below. Ferromagnetic materials are strongly attracted by magnets. They lose their magnetic properties at temperatures above the Curie point (770 ° C for Fe, 358 ° C for NI, 1120 ° C for CO) and behave like paramagnetics for which induction B. up to very high tension values H. It is proportional to her - exactly the same way as it takes place in a vacuum. Many elements and compounds are paramagnetic at all temperatures. Paramagnetic substances are characterized by maternalized in an external magnetic field; If this field is turned off, paramagnetics are returned to a slight state. Magnetization in ferromagnets is saved and after turning off the external field.

In fig. 2 shows a typical hysteresis loop for magnetically solid (with large losses) ferromagnetic material. It characterizes the ambiguous dependence of the magnetization of the magnetically ordered material from the tension of the magnetizing field. With an increase in the magnetic field intensity from the original (zero) point ( 1 ) Magnetization goes on the bar code 1 –2 , and the value m. Significantly changes as the magnetization of the sample increases. At point 2 Saturation is achieved, i.e. With a further increase in tension, magnetization no longer increases. If now gradually reduce the amount H. to zero, then the curve B.(H.) no longer follows the path, but passes through the point 3 , Introducing the "memory" of the material about the "past story", from where and the name "Hysteresis". Obviously, while some residual magnetization is preserved (segment 1 –3 ). After changing the direction of the magnetizing field to the opposite curve IN (N.) Passing point 4 , with a segment ( 1 )–(4 ) Corresponds to the coercive force that impedes demagnetization. Further growth of values \u200b\u200b(- H.) leads the hysteresis curve in the third quadrant - plot 4 –5 . The following decrease in the value (- H.) to zero and then increase positive values H. will lead to a closure of hysteresis loops across points 6 , 7 and 2 .

Magnetically solid materials are characterized by a wide hysteresis loop covering a significant area in a diagram and therefore corresponding to large values \u200b\u200bof residual magnetization (magnetic induction) and coercive force. A narrow hysteresis loop (Fig. 3) is characteristic of magnetic soft materials - such as soft steel and special alloys with large magnetic permeability. Such alloys were created in order to reduce the hysteresis of energy losses. Most of these special alloys, like ferrite, have high electrical resistance, due to which not only magnetic losses are reduced, but also electrical due to vortex currents.

Magnetic materials with high permeability are manufactured by an annealing carried out withstanding at a temperature of about 1000 ° C, followed by leave (gradual cooling) to room temperature. At the same time, pre-mechanical and thermal processing are very significant, as well as the absence in the sample of impurities. For cores of transformers at the beginning of the 20th century. Silicon steel has been developed, the amount m. which increased with increasing silicon content. Between 1915 and 1920 there were Permalloi (Ni alloys with Fe) with a narrow narrow and almost rectangular hysteresis loop. Especially high magnetic permeability values m. For small values H. Alloys Hypernik (50% Ni, 50% Fe) and Mu-metal (75% Ni, 18% FE, 5% CU, 2% CR), whereas in Perminvar (45% Ni, 30% Fe, 25% CO ) Value m. Virtually constant in the wide range of field strength changes. Among modern magnetic materials should be mentioned by supermalla - alloy with the highest magnetic permeability (its composition includes 79% Ni, 15% FE and 5% Mo).

Theories of magnetism.

For the first time, a guessed that magnetic phenomena ultimately be reduced to electric, arose at Ampere in 1825, when he expressed the idea of \u200b\u200bclosed internal microtons circulating in each atom of the magnet. However, without any experienced confirmation of such currents in the substance (the electron was opened by J.Tomson only in 1897, and the description of the atom structure was given by Rutherford and Borok in 1913) this theory "faded". In 1852, V.Vebere expressed the assumption that each atom of magnetic substance is a tiny magnet, or a magnetic dipole, so that the total magnetization of the substance is achieved when all individual atomic magnets are built in a certain order (Fig. 4, b.). Weber believed that the molecular or atomic "friction" helps to preserve its streamlining. Contrary to the indignant influence of heat oscillations by this elementary magnets. His theory was able to explain the magnetization of the bodies when contact with the magnet, as well as their demagnetization during impact or heating; Finally, the "reproduction" of magnets was also explained when cutting the magnetized needle or magnetic rod into parts. And yet, this theory did not explain the origin of the elementary magnets themselves, nor the phenomena of saturation and hysteresis. Weber Theory was improved in 1890 J. Eving, replaced by its atomic friction hypothesis idea of \u200b\u200binteratomic restrictive forces, helping to maintain the ordering of elementary dipoles that constitute a permanent magnet.

The approach to the problem proposed by the ampere once received a second life in 1905, when P. Luzheven explained the behavior of paramagnetic materials, attributing each atom the internal uncompensated electron current. According to Lanzhen, it is these currents that form a tiny magnets, chaotic oriented, when there is no external field, but purchasing an ordered orientation after its application. At the same time, the approach to full ordering corresponds to the saturation of magnetization. In addition, Lanzhen introduced the concept of a magnetic moment equal to a separate atomic magnet, the product of the "magnetic charge" of the pole to the distance between the poles. Thus, weak magnetism of paramagnetic materials is due to the total magnetic moment created by uncompensated electron currents.

In 1907, P. Veis introduced the concept of "domain", which became an important contribution to the modern theory of magnetism. Wesis represented domains in the form of small "colonies" of atoms, within which the magnetic moments of all atoms are forced to preserve the same orientation due to some causes, so that each domain is magnetized to saturation. A separate domain may have linear dimensions of about 0.01 mm and, accordingly, the volume of about 10 -6 mm 3. Domains are separated by the so-called Bloch walls whose thickness does not exceed 1000 atomic sizes. "Wall" and two oppositely oriented domain are schematically shown in Fig. 5. Such walls are "transition layers", which occurs a change in the direction of the magnetization of domains.

IN general On the initial magnetization curve, three sections can be distinguished (Fig. 6). In the initial section, the wall under the action of the external field moves through the thickness of the substance until the defect of the crystal lattice, which stops it. By increasing the field strength, you can force the wall to move on, through the middle section between the dashed lines. If after that the field strength is re-reduced to zero, then the walls will not return to its original position, so that the sample will remain partially magnetized. This explains the hysteresis of the magnet. At the final section of the curve, the process is completed by saturation of the sample magnetization due to the ordering of the magnetization within the latest unordered domains. Such a process is almost completely reversible. The magnetic hardness show those materials in which the nuclear grille contains many defects that prevent the movement of inter-domestic walls. This can be achieved by mechanical and heat treatment, for example, by compressing and subsequent sintering the powder material. In alloys and their analogues, the same result is achieved by fusion of metals in a complex structure.

In addition to paramagnetic and ferromagnetic materials, there are materials with so-called antiferromagnetic and ferrimagnetic properties. The difference between these types of magnetism is explained in Fig. 7. Based on the presentation of domains, paramagnetism can be viewed as a phenomenon due to the presence in the material of small groups of magnetic dipoles in which individual dipoles interact very poorly with each other (or do not interact at all) and therefore only random orientations take in the absence of an external field ( Fig. 7, but). In the ferromagnetic materials, within each domain, there is a strong interaction between individual dipoles, leading to their ordered parallel lineing (Fig. 7, b.). In antiferromagnetic materials, on the contrary, the interaction between individual dipoles leads to their anti-parallel ordered lining, so that the total magnetic moment of each domain is zero (Fig. 7, in). Finally, in ferrimagnetic materials (for example, ferrites), both parallel and anti-parallel streamlining (Fig. 7, g.), The result is weak magnetism.

There are two convincing experimental confirmations of the existence of domains. The first of them is the so-called Barkhausen effect, the second is the method of powder figures. In 1919, Barkhausen found that when the external field is applied to a sample of ferromagnetic material, its magnetization changes in small discrete portions. From the point of view of the domain theory, it is nothing more than the jump-like promotion of the cross-wall wall, which meets the individual delaying defects on its way. This effect is usually detected using a coil into which the ferromagnetic crash or wire is placed. If you alternately bring to the sample and remove a strong magnet from it, the sample will be magnified and rechangeed. Scrolling changes in the magnetization of the sample change the magnetic flux through the coil, and the induction current is excited. The voltage arising from this in the coil is enhanced and fed to the inlet of the pair of acoustic headphones. Clicks perceived through headphones indicate a jump-shaped change in magnetization.

To identify the domain structure of the magnet by the method of powder figures on a well-polished surface of the magnetized material, a drop of a colloidal suspension of ferromagnetic powder (usually Fe 3 O 4) is applied. Powder particles settled mainly in places of maximum inhomogeneity of the magnetic field - at the borders of the domains. Such a structure can be studied under a microscope. A method based on the passage of polarized light through transparent ferromagnetic material was also proposed.

The initial theory of Weiss magnetism in its main features has kept its value to the present, having received, however, an updated interpretation based on the representation of uncompensated electron spins as a factor defining atomic magnetism. The hypothesis about the existence of his own moment at the electron was put forward in 1926 S. Haudsmitomit and J. Yulebeck, and now it is electrons as "elementary magnets" as the spin carriers.

To explain this concept, we consider (Fig. 8) a free atom of iron - typical ferromagnetic material. His two shells ( K. and L.) The nearest to the kernel is filled with electrons, and two of them are placed two, and on the second - eight electrons. IN K.- The spin of one of the electrons is positive, and the other is negative. IN L.- The break (more precisely, in two submarines) in four of the eight electrons are positive, and others have negative backs. In both cases, the spins of the electrons within one shell are fully compensated, so that the full magnetic moment is zero. IN M."The situation is different, because of the six electrons located in the third submarine, five electrons have backs directed in one direction, and only the sixth to another. As a result, four uncompensated spin remain, which causes the magnetic properties of the iron atom. (In external N.- The break is only two valence electrons, which do not give the contribution to the magnetism of the iron atom.) Similarly explains magnetism and other ferromagnets, such as nickel and cobalt. Since the adjacent atoms in the iron sample strongly interact with each other, and their electrons are partially collectivized, such an explanation should be considered only as a visual, but very simplified scheme of the real situation.

The theory of atomic magnetism, based on the electron spin, reinforce two interesting gyromagnetic experiments, one of which was carried out by A. Einstein and Vde Gaaz, and the other is S. Barnett. In the first of these experiments, the cylindrik from the ferromagnetic material was suspended as shown in Fig. 9. If the winding is skipping the current, the cylinder turns around its axis. When the current direction is changed (and, consequently, the magnetic field) is rotated in the opposite direction. In both cases, the rotation of the cylinder is due to the ordering of electronic spins. In the Barnett experiment, on the contrary, also suspended cylindrik, sharply given to the state of rotation, is magnetized in the absence of a magnetic field. This effect is explained by the fact that the magnetic moment is rotated, a gyroscopic moment is created, striving to rotate spin moments in the direction of its own axis of rotation.

For a more complete explanation of the nature and origin of short-range forces, ordering neighboring atomic magnets and opposing the disordering influence of thermal motion, it should be referred to for quantum mechanics. The quantum-mechanical explanation of the nature of these forces was proposed in 1928 V.Gaisenberg, who postulated the existence of exchange interactions between neighboring atoms. Later, Bethy and J. Slether showed that the exchange forces increase significantly with a decrease in the distance between atoms, but at the achievement of some minimal interatomic distance fall to zero.

Magnetic properties of matter

One of the first extensive and systematic studies of the magnetic properties of the substance was undertaken by P.Curi. He found that in its magnetic properties, all substances can be divided into three classes. The first includes substances with sharply pronounced magnetic properties, similar to the properties of iron. Such substances are called ferromagnetic; Their magnetic field is noticeable at considerable distances ( cm. above). In the second grade there are substances called paramagnetic; Their magnetic properties are generally similar to the properties of ferromagnetic materials, but much weaker. For example, the force of attraction to the poles powerful electromagnet It can snatch from your hands an iron hammer, and to detect the attraction of the paramagnetic substance to the same magnet, it is necessary, as a rule, very sensitive analytical scales. The last, third class includes so-called diamagnetic substances. They are repelled by electromagnet, i.e. The force acting on diamagnetics is directed opposite to the one that acts on ferro and paramagnetics.

Measurement of magnetic properties.

When studying magnetic properties, two types of measurements are most important. The first of them is measuring the force acting on the sample near the magnet; This determines the magnetization of the sample. The second is the measurements of the "resonant" frequencies associated with the magnetization of the substance. Atoms are tiny "gyroscopes" and in the magnetic field are preceded (as a conventional top under the influence of the torque generation of gravity) with a frequency that can be measured. In addition, the free adjustable particles moving at a right angle to the magnetic induction lines, the force acts as on the electronic current in the conductor. It makes the particle move along a circular orbit, the radius of which is given by the expression

R. = mV/eB.,

where m. - mass of particles, v. - its speed, e. - her charge, and B. - Magnetic field induction. The frequency of such a circular motion is equal

where f. measured in hertz, e. - in the coulters, m. - in kilograms, B. - In Teslas. This frequency characterizes the movement of charged particles in a substance in a magnetic field. Both types of movements (precession and movement in circular orbits) can be excited by variable fields with resonant frequencies equal to "natural" frequencies characteristic of this material. In the first case, the resonance is called magnetic, and in the second - cyclotron (due to the similarity with the cyclical movement of the subatomic particle in the cyclotron).

Speaking about the magnetic properties of atoms, it is necessary to emphasize on their moment of momentum. The magnetic field acts on the rotating atomic dipole, striving to turn it and install parallel to the field. Instead, atom begins to precession around the direction of the field (Fig. 10) with a frequency depending on the dipole moment and the attached field strength.

The precession of atoms is not directly observation, since all sample atoms are precedes in different phases. If you apply a small variable field sent perpendicular to a constant ordering field, then a certain phase ratio is established between precessing atoms and their total magnetic moment begins to precessively with the frequency equal to the frequency of the precession of individual magnetic moments. The angular velocity of the precession is important. As a rule, this is the magnitude of the order of 10 10 Hz / Tl for the magnetization associated with electrons, and about 10 7 Hz / Tl for the magnetization associated with positive charges in atomic nuclei.

The schematic diagram of the installation for observing the nuclear magnetic resonance (NMR) is presented in Fig. 11. In a homogeneous permanent field between the poles, the studied substance is introduced. If then with a small coil, covering the tube, excite the radio frequency field, you can achieve a resonance at a certain frequency equal to the frequency of the precession of all nuclear "gyroscopes" of the sample. Measurements are similar to the configuration of the radio at the frequency of a certain station.

Magnetic resonance methods allow to investigate not only the magnetic properties of specific atoms and nuclei, but also the properties of their environment. The fact is that the magnetic fields in solids and molecules are inhomogeneous, since they are distorted by atomic charges, and the stroke parts of the experimental resonant curve are determined by the local field in the area of \u200b\u200bthe precessing kernel. This makes it possible to study the characteristics of the structure of a particular sample with resonant methods.

Calculation of magnetic properties.

The magnetic induction of the Earth field is 0.5 h 10 -4 T., while the field between the poles of a strong electromagnet is about 2 tles and more.

The magnetic field created by any current configuration can be calculated using the Bio-Savara - Laplace formula for magnetic induction of the field generated by the current element. Calculation of the field created by contours of different shapes and cylindrical coils, in many cases is very complicated. The following are formulas for a number of simple cases. Magnetic induction (in teslas) field created by a long direct wire with a current I.

The field of the magnetized iron rod is similar to the outer field of the long solenoid with the number of amp-turns per unit of length, corresponding to the current in the atoms on the surface of the magnetized rod, since the currents inside the rod are mutually compensated (Fig. 12). By the name of the ampere, such a surface current is called Ammeovsky. Magnetic field tension H A.generated by ammel current equal to the magnetic moment of the unit volume of the rod M..

If an iron rod is inserted into the solenoid, then besides the solenoid current creates a magnetic field H.The streamlining of atomic dipoles in the magnetized material of the rod creates magnetization M.. In this case, the complete magnetic flux is determined by the sum of the real and amper currents, so B. = m.0(H. + H A.), or B. = m.0(H + M.). Attitude M./H. called magnetic susceptibility and indicated by the Greek letter c.; c.- a dimensionless value that characterizes the ability of the material to be magnetized in a magnetic field.

Value B./H., characterizing the magnetic properties of the material, is called magnetic permeability and is indicated through m A., and m A. = m.0m.where m A. - absolute, and m. - relative permeability,

In ferromagnetic substances c. It can have very large meanings - 10 4 EK 10 6. Value c. Paramagnetic materials are slightly larger than zero, and diamagnetic - a little less. Only in vacuum and in very weak fields of magnitude c. and m. constant and do not depend on the external field. Induction dependence B. from H. Usually nonlinear, and its graphics, so-called. Magnetization curves for different materials and even at different temperatures can differ significantly (examples of such curves are shown in Fig. 2 and 3).

The magnetic properties of the substance are very complex, and a thorough analysis of the structure of atoms, their interactions in molecules, their clashes in gases and their mutual influence in solids and liquids are needed; Magnetic properties of liquids are still the least studied.

Everyone kept a magnet in his hands and amused them in childhood. Magnets can be very different in shape, sizes, but all the magnets have a common property - they attract iron. It seems that they themselves are made of iron, in any case, from some metal for sure. There are, however, "black magnets" or "stones", they also attract the glands strongly, and especially each other.

But they are not like metal, they are easily frightened as glass. The farm magnets contains many useful cases, for example, conveniently with their help to "pin" paper sheets to iron surfaces. Magnet is convenient to collect lost needles, so, as we see, it is a completely unfasteless thing.

Science 2.0 - Large jump - Magnets

Magnet in the past

More Ancient Chinese more than 2,000 years ago knew about magnets, at least what this phenomenon can be used to select direction on travel. That is, a compass was invented. Philosophers B. ancient Greece, people are curious, collecting various amazing factsFaced with magnets in the vicinity of the city of Magnes in Malaya Asia. There they discovered strange stones that could attract iron. At the time, it was no less awesome than could be in our time aliens.

Even more surprising it seemed that the magnets were far from all metals, but only iron, and the iron itself is capable of becoming a magnet, although not so strong. It can be said that the magnet attracted not only iron, but also the curiosity of scientists, and moved a lot forward such science as physics. Fales from the Milet wrote about the "Magnet's Magnet", and the Roman Tit Lucretia Kar - about the "raging movement of iron sawdust and rings", in his essay "On the nature of things". He could already notice the presence of two poles from a magnet, which later, when the sailor began to use the compass, got the names in honor of the parties of the world.

What is a magnet. Simple words. A magnetic field

The magnet took seriously

The nature of the magnets could not explain for a long time. With the help of magnets, new continents opened (sailors still belong to the compass with great respect), but no one knew anything about the very nature of magnetism. Works were carried out only on the improvement of the compass, which was still engaged in the geographer and the navigator Christopher Columbus.

In 1820, the Danish scientist Hans Christian Ersted did the most important discovery. He installed the action of the wire with an electric shock on a magnetic arrow, and as a scientist, found out the experiments as it happens in different conditions. In the same year, the French physicist Henri Ampere made a hypothesis about elementary circular currents occurring in magnetic molecules. In 1831, the Englishman Michael Faradays using an insulated wire and magnet coil conducts experiments showing that the mechanical work can be turned into an electric current. It also establishes the law of electromagnetic induction and introduces the concept of "magnetic field" into appeal.

Faraday law establishes the rule: for a closed contour, the electromotive force is equal to the rate of changing the magnetic flux passing through this circuit. In this principle, all electrical machines work are generators, electric motors, transformers.

In 1873, Scottish scientist James K. Maxwell reduces magnetic and electrical phenomena into one theory, classical electrodynamics.

Substances that are able to magnify, received the name of ferromagnets. This name binds magnets with iron, but besides it, the ability to magnetize is still found in nickel, cobalt, and some other metals. Since the magnetic field has already passed into the field of practical use, then the magnetic materials have become a matter of much attention.

Experiments with alloys from magnetic metals and various additives in them began. It cost the resulting materials very expensive, and if Werner Siemens did not occur to the idea to replace the magnet steel, magnetized by a relatively small current, then the world would not see the electric tram and Siemens. Siemens still engaged in telegraph devices, but here he had a lot of competitors, and the electric tram gave a lot of money from the company, and ultimately pulled the rest.

Electromagnetic induction

Main values \u200b\u200brelated to magnets in the technique

We will be interested in mainly magnets, that is, ferromagnets, and leave a bit aside the rest, a very extensive region of magnetic (better to say electromagnetic, in memory of Maxwell) phenomena. We will have those that are accepted in C (kilogram, meter, second, amps) and their derivatives:

l. Field tension, H, A / m (amp per meter).

This value characterizes the field strength between parallel conductors, the distance between which is 1 m, and the current flow 1 A. The field strength is a vector magnitude.

l. Magnetic induction, B, tesla, magnetic flux density (Weber / M.KV.)

This current ratio through the conductor to the length of the circle, on the radius on which we are interested in the value of induction. The circle lies in the plane that the wire crosses perpendicularly. This includes a multiplier called magnetic permeability. This is a vector magnitude. If you mentally look into the end of the wire and assume that the current flows towards us, then the magnetic power circles "rotate" clockwise, and the induction vector is applied to the tangent and coincides with them in the direction.

l. Magnetic permeability, μ (relative value)

If we take the magnetic permeability of the vacuum for 1, then for other materials we will receive the appropriate values. For example, for air, we will get the magnitude, almost the same as for vacuum. For iron, we get substantially large quantities, so that you can figure out (and very accurately) to say that the iron "pulls" the power magnetic lines. If the field strength in the coil without a core will be equal to H, then we get μH with the core.

l. Coercive force, A / m.

The coercive force shows how magnetic material resists demagnetization and reclamation. If the current in the coil is completely removed, then the core will be residual induction. To make it equal to zero, you need to create a field of some tension, but reverse, that is, to put the current in the opposite direction. This tension is called coercive force.

Since magnets in practice are always used in some connection with electricity, it is not to be surprised that such an electrical value as amp is used to describe their properties.

From the said it follows the possibility, for example, a nail, which has been involved in a magnet, to become a magnet itself, albeit weaker. In practice, it turns out that even children who have fun with magnets know about it.

Magnets in the technique there are different requirements, depending on where these materials go. Ferromagnetic materials are divided into "soft" and "hard". The first go to the manufacture of cores for instruments, where the magnetic stream is constant or variable. You can't do a good self-magnet of soft materials. They are too easily demagned and here it is the most valuable property here, since the relay should "release" if the current is turned off, and the electric motor should not warm up - excessive energy is spent on the magnetization.

What does a magnetic field look like? Igor Beletsky

Permanent magnets, that are, those that are called magnets and require hard materials for their manufacture. The hardness is meant magnetic, that is, a large residual induction and a large coercive force, since, as we have seen, these values \u200b\u200bare closely related. Magnets are carbon, tungsten, chromium and cobalt steel. Their coercive force reaches the values \u200b\u200bof about 6500 cars.

There are special alloys called Alny, Alnisi, Alnic and many others, as you can guess in them enter aluminum, nickel, silicon, cobalt in different combinations, which have a greater coercive force - up to 20,000 ... 60000 vehicles. Such a magnet is not so easy to tear off the iron.

There are magnets specifically designed to work at an increased frequency. This is a lot of famous "round magnet". It is "mined" from the unsuitable speaker from the column of the music center, or car radio or even the TV of past years. This magnet is made by sintering iron oxides and special additives. Such a material is called ferrite, but not every ferrite is specifically magnetized. And in the speakers it is used for reasons of reducing useless losses.

Magnets. Discovery. How it works?

What happens inside the magnet?

Due to the fact that the atoms of substances are peculiar "bunches" of electricity, they can create their magnetic field, but only in some metals having a similar atomic structureThis ability is very much expressed. Both iron and cobalt, and nickel stand in the periodic Mendeleev system near, and have similar structures of electron shells, which converts atoms of these elements into microscopic magnets.

Since the metals can be called the frozen mixture of various crystals of a very small size, then it is clear that the magnetic properties of such alloys can be very much. Many groups of atoms can "deploy" their own magnets under the influence of neighbors and external fields. Such "communities" is called magnetic domains, and form very bizarre structures, which are still being studied with interest with physicists. It has great practical importance.

As already mentioned, magnets can have almost atomic sizes, so the smallest size The magnetic domain is limited to the crystal size in which the magnetic metal atoms are built. This explains, for example, almost a fantastic record density on modern hard disks of computers, which, apparently, will still grow while the discs do not appear competitors more serious.

Gravity, Magnetism and Electricity

Where are the magnets apply?

Whose cores are magnets from magnets, although they are usually called simply cores, magnets find many more applications. There are stationery magnets, magnets for latching furniture doors, magnets in chess for travelers. These are all magnets known.

More rare species include magnets for charged particle accelerators, these are very impressive facilities that can weigh tens of tons and more. Although now experimental physics has risen the grass, with the exception of the part that immediately brings super-profits on the market, and almost nothing else.

Another curious magnet is installed in a medical workfield, which is called a magnetic resonance tomograph. (Actually, the method is called NMR, nuclear magnetic resonance, but in order not to scare the people who are not strong in physics in the mass, it was renamed.) For the device, the observed object (patient) in a strong magnetic field is required, and the corresponding magnet has frightening dimensions. And the form of the Devil Coffin.

The person is put on the couch, and rolled through the tunnel in this magnet, while the sensors scan the place that interests doctors. In general, nothing terrible, but some claustrophobic comes to degree of panic. Such willingly give themselves to cut themselves, but will not agree to the MRI inspection. However, who knows how a person feels in an unusually strong magnetic field with an induction of up to 3 Tesla, after he paid for good money.

To obtain such a strong field, superconductivity often use, cooling the magnet coil with liquid hydrogen. This makes it possible to "pump" the field without fears that the heating of the wires with a strong current will limit the capabilities of the magnet. This is a completely notable installation. But magnets made of special alloys that do not require the addition of current, cost much more expensive.

Our land is also big, although not a very strong magnet. It helps not only the owners of a magnetic compass, but also saves us from death. Without it, we would be killed by solar radiation. The pattern of the magnetic field of the Earth, modeled by computers according to the observations from the space looks very impressive.

Here is a small answer to the question, about what a magnet is in physics and technology.

4. Application of magnets in different areas of modern society

The main use of the magnet finds in electrical engineering, radio engineering, instrument making, automation and telemechanic. Here ferromagnetic materials go to the manufacture of magnetic pipelines, relays, etc. .

Electromachine generators and electric motors - rotational type machines transforming either mechanical energy In electrical (generators), or electrical in mechanical (engines). The action of the generators is based on the principle of electromagnetic induction: in a wire moving in a magnetic field, an electromotive force (EMF) is guided. The effect of electric motors is based on the fact that the force placed in the transverse magnetic field is valid.

Magnetoelectric devices. In such devices, the power of the interaction of the magnetic field is used with a current in the turns of the winding of the movable part, seeking to turn the latter.

Induction electricity meters. The induction meter is nothing but a low-power AC motor with two windings - current and voltage winding. A conductive disk placed between windings rotates under the action of torque proportional to power consumed. This moment is equalized by currents in the disk with a permanent magnet, so the frequency of rotation of the disk is proportional to the power consumption.

Electric wrist Watch Food miniature battery. It requires much less details for their work than in the mechanical clock; Thus, the scheme of typical electric portable clock includes two magnets, two inductors and a transistor.

Dynamometer - a mechanical or electrical device for measuring the force of the thrust or torque of the machine, machine or engine.

Brake dynamometers are of a wide variety of structures; These include, for example, brake penetration, hydraulic and electromagnetic brakes.

The electromagnetic dynamometer can be made in the form of a miniature instrument suitable for measurement of the characteristics of small-sized engines.

The magnetic properties of the substance are widely used in science and technology as a means of studying the structure of various bodies. So there were sciences:

Magnetochemistry - section of physical chemistry, in which the connection between the magnetic and chemical properties of substances is studied; In addition, the magnetochemistry explores the effect of magnetic fields into chemical processes. Magnetichemia relies on modern physics of magnetic phenomena. The study of the connection between magnetic and chemical properties allows us to find out the peculiarities of the chemical structure of the substance.

Magnetic flaw detection, defect search method based on the study of the magnetic field distortion arising in places of defects in products from ferromagnetic materials.

Particle accelerator, installation in which the electrons, protons, ions and other charged particles with an energy significantly exceeding thermal energy are obtained using electrical and magnetic fields.

In modern accelerators, numerous and diverse species Techniques, incl. Powerful precision magnets.

In medical therapy and diagnosis, the officers play an important practical role. Many hospital institutions around the world today have at their disposal small electronic linear accelerators generating intensive X-ray radiation used for tumor therapy. Nicely use cyclotons or synchrotrons that generate proton beams. The advantage of protons in the treatment of tumors in front of X-ray radiation consists of a more localized energy release. Therefore, proton therapy is particularly effective in the treatment of brain tumors and eyes, when damage to surrounding healthy tissues should be as minimal.

Representatives of various sciences take into account magnetic fields in their research. The physicist measures the magnetic fields of atoms and elementary particles, the astronomer studies the role of space fields in the process of forming new stars, the geologist for the anomalies of the magnetic field of the Earth finds the deposits of magnetic ores, from recently, biology is also actively involved in the study and use of magnets.

The biological science of the first half of the 20th century confidently described life functions, not at all given the existence of any magnetic fields. Moreover, some biologists considered it necessary to emphasize that even a strong artificial magnetic field does not have any influence on biological objects.

In encyclopedias about the effect of magnetic fields on biological processes, nothing was said. In the scientific literature of the whole world, isolated positive considerations about the biological effect of magnetic fields annually appeared. However, this weak river could not melt the iceberg distrust even to the formulation of the problem itself ... and suddenly the river turned into a stormy stream. Avalanche of magnetobiological publications, as if having broken down from some vertices, since the beginning of the 60s, the skeptical statements are increasingly increasing and swells.

From the Alchemists of the XVI century and to the present day, the biological effect of the magnet has found fans and critics. Repeatedly for several centuries observed bursts and decals of interest in medical action magnet. With it, they tried to treat (and not unsuccessfully) nervous diseases, toothpick, insomnia, pain in the liver and in the stomach - hundreds of disease.

For therapeutic purposes, the magnet has become used, probably earlier than to determine the parties of the Light.

As a local exterior and as an amulet, the magnet has enjoyed great success among the Chinese, Hindus, Egyptians, Arabs, Greeks, Romans, etc. The philosopher Aristotle and the historian of Pliny are mentioned about his therapeutic properties.

In the second half of the 20th century, magnetic bracelets have widely spread, which are beneficial on patients with blood pressure impairment (hypertension and hypotension).

In addition to permanent magnets, electromagnets are used. They are also used for a wide range of problems in science, technology, electronics, medicine (nervous diseases, disease vessel diseases, cardiovascular - vascular diseases, cancer).

Most of all, scientists are inclined to think that magnetic fields increase the body's resistance.

There are electromagnetic blood velocity meters, miniature capsules, which can be moved through the blood vessels using external magnetic fields to expand them, take samples at certain parts of the path or, on the contrary, locally output from the capsules various medicines.

The magnetic method of removing metal particles from the eye is widespread.

Most of us are known to study the work of the heart using electrical sensors - an electrocardiogram. The electrical pulses produced by the heart create a magnetic field of the heart, which in max values \u200b\u200bis 10-6 voltages of the Earth magnetic field. The value of magnetocardiography is that it allows you to get information about electrically "silent" regions of the heart.

It should be noted that biologists are now asking physicists to give the theory of the primary biological action mechanism of the magnetic field, and physicists in response require more proven biological facts from biologists. Obviously, there will be a successful cooperation of various specialists.

An important link uniting magnetobiological problems is the reaction nervous system on magnetic fields. It is the brain first that reacts to any changes in the external environment. It is the study of his reactions that will be the key to solving many problems of magnetobiology.

Among the technological revolutions of the end of the XX century, one of the most important is the translation of consumers for atomic fuel. And again magnetic fields were in the center of attention. Only they will be able to curb the wayward plasma in the "peaceful" thermonuclear reaction, which should come to replace the reactions of division of radioactive uranium and thorium nuclei.

What else to burn? - an obsessive refrain sounds the question, forever tormented energy. For quite a long time, we saw firewood, but they have low energy intensity, and therefore the wood civilization is primitive. Today's our welfare is based on burning fossil fuel, however, the easily accessible reserves of oil, coal and natural gas slowly, but rightly dried. Will-Neils have to reorient the fuel and energy balance of the country for something else. In the future century, the remains of organic fuel will have to preserve the raw materials of chemistry. And the main power grid, as you know, will become nuclear fuel.

The idea of \u200b\u200bmagnetic thermal insulation of plasma is based on the well-known property of electrically charged particles moving in a magnetic field, to curb its trajectory and move along the spiral of the field lines. This curvature of the trajectory in an inhomogeneous magnetic field leads to the fact that the particle is pushed into an area where the magnetic field is weaker. The task is to surround the plasma from all sides to the stronger field. This task is solved in many laboratories in the world. The magnetic retention of plasma was discovered by Soviet scientists, which in 1950 were offered to keep the plasma in the so-called magnetic traps (or, as often they are called, in magnetic bottles).

An example of a very simple system for magnetic retention of a plasma can be a trap with magnetic corks or mirrors (proboscotron). The system is a long tube in which a longitudinal magnetic field has been created. At the ends of the pipe, more massive windings are wound than in the middle. This leads to the fact that magnetic power lines at the ends of the pipe are ground and the magnetic field in these areas is stronger. Thus, the particle that fell into a magnetic bottle cannot leave the system, for it would have to cross the power lines and due to the Lorentz power to "wind" on them. In this principle, a huge magnetic trap of the "Lental-1" installation was built, brushed at the Institute of Atomic Energy named after I.V. Kurchatova in 1958 Vacuum camera "Log-1" has a length of 19 m with internal diameter 1.4 m. The average diameter of the winding, creating a magnetic field, is 1.8 m, field strength in the middle of the chamber 0.5 TL, in traffic jams 0.8 T..

The cost of electricity obtained from thermonuclear power plants will be very low due to the cheaper raw materials (water). The time will come when the power plants will produce literally the oceans of electricity. With the help of this electricity, it will be possible, perhaps not only dramatically change the living conditions on Earth - turn reversal rivers, dry the swamps, wet the desert, - but also change the appearance of the surrounding space - to populate and "revive" the moon, surround Mars atmosphere.

One of the main difficulties on this path is the creation of a magnetic field of a given geometry and magnitude. Magnetic fields in modern thermonuclear traps are relatively small. However, if we take into account the huge amounts of cameras, the absence of a ferromagnetic core, as well as special requirements for the form of a magnetic field, impede the creation of such systems, it should be recognized that the available traps - a great technical achievement.

Based on the foregoing, it can be concluded that at present there is no industry in which the magnetism or the phenomenon of magnetism would not be used.

5. superconductors and their use magnet superconductor

Superconductors are often referred to as the key to the electrical engineering of the future. This is explained by their truly amazing properties. In fact, superconductors as special materials do not exist. These are ordinary materials from the Mendeleev table elements that certain conditions An unusual properties appear. Aluminum, for example, is considered a good conductor, it is not bad to pass warmly and in its thicker slightly enhances the magnetic field (paramagnet). When cooling below 1.2, the electrical conductivity of aluminum increases infinitely (superconductor), thermal conductivity is also strongly deteriorated (thermal insulator), and the magnetic field can no longer penetrate (diamagnet). It would seem that for achieving so useful qualities it is necessary to pay too expensive - the achievement of low temperatures - the pleasure is not cheap. It turned out, however, that the cost of refrigerators and thermal protection of cold zones is incomparable with achievable advantages. It became possible without excessive costs to get huge currents (a few thousand times large than in ordinary conductors) and huge magnetic fields with modest cross sections of the tires: it is extremely important when creating powerful electric power devices.

It is clear that to create more power generators, new design solutions and materials will be needed. In this regard, special hopes scientists and engineers are pinned on superconductivity. No wonder one of the main directions for the development of science are theoretical and experimental studies in the field of superconducting materials, and one of the main areas of development of technology is the development of superconducting turbogenerators. Superconducting electrical equipment will allow dramatically to increase electrical and magnetic loads in the elements of devices and thanks to this dramatically reduce their dimensions. In the superconducting wire, the current density is permissible, 10 ... 50 times higher than the current density in conventional electrical equipment. Magnetic fields can be brought to values \u200b\u200bof the order of 10 T., compared with 0.8 ... 1 TL in conventional machines. If we consider that the sizes of electrical devices are inversely proportional to the product of the valid current density to the induction of the magnetic field, it is clear that the use of superconductors will reduce the size and mass of electrical equipment many times!

Many obstacles themselves disappear, if you use the effect of superconductivity and apply superconducting materials. Then the losses in the rotor winding can be practically reduced to zero, since d.C. Will not meet resistance in it. And if so, the efficiency of the machine rises. The high force current flowing over the superconducting winding creates such a strong magnetic field, which is no longer necessary to apply steel magnetic core, traditional for any electric machine. Elimination began to reduce the mass of the rotor and its inertia. Creating cryogenic electrical machines - not tribute to fashion, but the need, natural consequence of scientific and technological progress. And there is every reason to argue that by the end of the century superconducting turbogenerators with a capacity of more than 1000 MW will work in power systems.

Energy needs not only cold generators. Several dozen superconducting transformers were already manufactured and tested (the first of them was built by Americans McIn in 1961; the transformer worked at 15 kW). There are projects of superconducting transformers to power up to 1 million kW. With sufficiently large capacities, superconducting transformers will be easier than usual by 40 ... 50% with approximately the same power loss transformers (in these calculations, the capacity of the lifesteller) is also taken into account. They are associated with the need to protect the transformer from the exit of it from the superconducting state during overloads, short circuits, overheating, when the magnetic field, current or temperature can achieve critical values.

IN last years It is becoming increasingly close to the fulfillment of the dream of superconducting power lines. The increasing need for electricity makes a very attractive transmission of high power over long distances. Soviet scientists convincingly showed the prospect of superconducting transmission lines. The cost of lines will be comparable to the value of ordinary air lines Electricity transmission (cost of superconductor, if we consider the high value of the critical density of its current compared to the economically appropriate current density in copper or aluminum wires, is small) and below the cost cable lines. It is assumed to carry out superconducting power lines: between the final transmission points in the ground, a liquid nitrogen pipeline is laid in the ground. Inside this pipeline is a pipeline with liquid helium. Helium and nitrogen occurred in pipelines due to the creation between the initial and final points of the pressure difference. Thus, the vibrant pumping stations will be only at the ends of the line. Liquid nitrogen can be used simultaneously as a dielectric. The helium pipeline is maintained inside the nitrogen dielectric racks (in most insulators, dielectric properties are improved at low temperatures). The helium pipeline has vacuum insulation. The inner surface of the liquid helium pipeline is covered with a superconductor layer. Losses in such a line, taking into account the inevitable losses at the ends of the line, where the superconductor should be shaked with the tires at normal temperature, will not exceed several more percentages, and in conventional power lines of loss in 5 ... 10 times more!

The basis of the energy of the early XXI century can be atomic and thermonuclear stations with extremely powerful electric generators. Electric fieldsgenerated by superconducting electromagnets, mighty rivers be able to flow over superconducting power lines to superconducting energy storage devices, from where it will be selected by consumers. Power plants will be able to evenly produce power and day, and at night, and their release from planned regimes should increase the efficiency and service life of the main aggregates.

Space solar stations can be added to ground power plants. Having hinged over fixed points of the planet, they will have to convert the sun's rays into short-wave electromagnetic from the remote to send focused energy streams to ground converters in industrial currents. All electrical equipment of ground-space electrical systems It should be superconducting, otherwise loss in conductors of finite electrical conductivity will be apparently unacceptable.

Conclusion

The worldview and well-being of a person sufficiently depends on the progress of science.

A small trembling arrow, from one end painted black, from the other - in red, we are obliged to amazing discoveries. Unknown worlds, exotic animals, fragrant islands, ice continents and who do not know the people's civilization appeared before the eyes of the amazed "drivers of frigates", which have accomplished their way with a small arrow of the compass ...

In a huge arsenal of funds modern science Magnet occupies a perfect place. Without it, no study is impossible, no science, no industry, no civilized life. If you remember also that not possess the Earth by a magnetic field, it would now be a planet as Mars covered with cosmic radiation as Mars, then you can feel something like gratitude to magnets.

But besides thanks, the magnet is worthy and respect - because if you think in a historical scale, then you have to confess that we can still say that we can say about the nature of the magnet attraction.

The issue of magnetic attraction Another hundred years will worry the minds of boys and scientists. I will not overestimate your knowledge. Who does it, often gets to see. Recall that it was written about electricity in 1755 in one London weekly: "Electricity is a force well-studied by man. It is successfully used to treat diseases, this force is able to accelerate the development of plants. "

These words were written before Faraday, Ampere, Maxwell, when people can now be safely argued, did not know anything about electricity. And now, in the second half of the 20th century, it is unlikely that some scientist will find the courage to say: "Electricity is a force well-studied by man."

We know a lot about electricity and magnetism and learn more and more every day. But on one problem there are other, no less complex and interesting. Life will always be full of mysteries. And along with the most complex - mystery life and the mystery of the Universe - the mystery of the magnet will always give food for the inquisitive mind.

Albert Einstein remembered the day when he, a four-year-old child, gave a new toy - compass. For life, he retained the children's surprise with the wonderful properties of the magnet, the most properties that thousands of years ago were worried about our ancestors.

It is unlikely that there will be a person who will have a courage to say: "I have suffered a mystery of the magnet!" However, scientists who have known a surprisingly small toliary of secrets were able to create devices capable of competing with the strongest magnets created by nature.

Bibliography

1. Big Soviet Encyclopedia. Publisher "Soviet Encyclopedia", M., 1974.

2. Dyagilev, F.M. From the history of physics and life of her creators: a textbook for universities / FM Dyagilev. - M.: Education, 1986. - 280 s.

3. Kabardin, O.F. Physics: Ref. Materials: studies. Manual for students. / O.F. Kabardin. - 3rd ed. - M.: Education, 1991. - 367С.: IL.

4. Kartsev, V.P. Magnet for three thousand years / V.P. Carts. - M.: Knowledge, 1986. - 230 s.

5. Elk, V.A. History and philosophy of science. Basics of the course: Tutorial / V.A. Elk. - M.: Publisher - Trading Corporation Dashkov and K 0, 2004.- 404 p.

6. Milkovskaya, L.B. We repeat the physics: a tutorial for universities / L.B. Milkovskaya. - M.: Higher School, 1991- 307c.: Il.

7. Simonenko, OD Electrical science in the first half of the XX century. / O.D. Simonenko. - M.: Knowledge, 1988. - 325С.

8. Modern electronics (50-80-Е) / V.P. Borisov [and others]; Ed. V.P. Borisova, V.M. Rodionova. - M.: Omega-L, 1993. - 340 p.

9. Kholodov, Yu.A. Man in magnetic web: / Yu.A. Colds. - M.: Knowledge, 1972 - 173 p.

10. Electromagnetic dynamometers // Science and technology. - 2008. - №5. - p.25-27

Electromachine generators and electric motors - rotational type machines, converting either mechanical energy into electrical (generators), or electrical in mechanical (engines). The action of the generators is based on the principle of electromagnetic induction: in a wire moving in a magnetic field, an electromotive force (EMF) is guided. The effect of electric motors is based on the fact that the force placed in the transverse magnetic field is valid.

Magnetoelectric devices. In such devices, the power of the interaction of the magnetic field is used with a current in the turns of the winding of the movable part, seeking to turn the latter.

Electric wristwatches are powered by a miniature battery. It requires much less details for their work than in the mechanical clock; Thus, the scheme of typical electric portable clock includes two magnets, two inductors and a transistor.

Dynamometer - a mechanical or electrical device for measuring the force of the thrust or torque of the machine, machine or engine.

Brake dynamometers are of a wide variety of structures; These include, for example, brake penetration, hydraulic and electromagnetic brakes.

The electromagnetic dynamometer can be made in the form of a miniature instrument suitable for measurement of the characteristics of small-sized engines.

The magnetic properties of the substance are widely used in science and technology as a means of studying the structure of various bodies. So there were sciences:

Magnetic flaw detection, defect search method based on the study of the magnetic field distortion arising in places of defects in products from ferromagnetic materials.

In modern accelerators, numerous and varied types of equipment are used, incl. Powerful precision magnets.

In medical therapy and diagnosis, the cervices play an important practical role. Many hospital institutions around the world today have at their disposal small electronic linear accelerators generating intensive X-ray radiation used for tumor therapy. Nicely use cyclotons or synchrotrons that generate proton beams. The advantage of protons in the treatment of tumors in front of X-ray radiation consists of a more localized energy release. Therefore, proton therapy is particularly effective in the treatment of brain tumors and eyes, when damage to surrounding healthy tissues should be as minimal.

From the Alchemists of the XVI century and to the present day, the biological effect of the magnet has found fans and critics. Repeatedly for several centuries, bursts were observed and the decline in interest in the medicinal action of the magnet. With it, they tried to treat (and not unsuccessfully) nervous diseases, dental pain, insomnia, pain in the liver and in the stomach - hundreds of diseases.

For therapeutic purposes, the magnet has become used, probably earlier than to determine the parties of the Light.

In the second half of the 20th century, magnetic bracelets have widely spread, which are beneficial on patients with blood pressure impairment (hypertension and hypotension).

In addition to permanent magnets, electromagnets are used. They are also used for a wide range of problems in science, technology, electronics, medicine (nerve diseases, limb vessel disease, cardiovascular diseases, cancer).

Most of all, scientists are inclined to think that magnetic fields increase the body's resistance.

The magnetic method of removing metal particles from the eye is widespread.

An important link uniting magnetobiological problems is the reaction of the nervous system for magnetic fields. It is the brain first that reacts to any changes in the external environment. It is the study of his reactions that will be the key to solving many problems of magnetobiology.

An example of a very simple system for magnetic retention of a plasma can be a trap with magnetic corks or mirrors (proboscotron). The system is a long tube in which a longitudinal magnetic field has been created. At the ends of the pipe, more massive windings are wound than in the middle. This leads to the fact that magnetic power lines at the ends of the pipe are ground and the magnetic field in these areas is stronger. Thus, the particle that fell into a magnetic bottle cannot leave the system, for it would have to cross the power lines and due to the Lorentz power to "wind" on them. In this principle, a huge magnetic trap of the "Lental-1" installation was built, brushed at the Institute of Atomic Energy named after I.V. Kurchatova In 1958, the Vacuum chamber "RUB-1" has a length of 19 m with an internal diameter of 1.4 m. The average diameter of the winding, creating a magnetic field, is 1.8 m, field strength in the middle of the chamber 0.5 TL, in traffic jams 0.8 T.

Based on the foregoing, it can be concluded that at present there is no industry in which the magnetism or the phenomenon of magnetism would not be used.

At the very beginning of work, it will be useful to give daily payments.

If, in some place, on moving bodies, possessing a charge, the force acts that does not act on fixed or devoid of body, they say that in this place is present a magnetic field - one of the forms of more general electromagnetic field .

There are bodies that can create a magnetic field around them (and the magnetic field strength is also valid for such a body), they say that these bodies are logied and have a magnetic moment, which is also determined by the body to create a magnetic field. Such bodies are called magnets .

It should be noted that different materials on divergent to an external magnetic field.

There are materials weakening external field intrabash – paramagnetics and reinforcing the external field inside – diamagnetics.

There are materials with a huge ability (in thousands of times) to strengthen the external field within themselves - iron, cobalt, nickel, gadolinium, alloys and compounds of these metals, they are called - Ferromagnets.

There are among ferromagnets materials that are a sufficient impact on them is a sufficiently strong external magnetic field themselves with magnets - this magnetically solid materials.

There are materials concentrating an external magnetic field and, while the nearest, behave like magnets; But if the external field disappears, they are not unpleasured by magnets - this magnetic materials

Introduction

We are accustomed to the magnet about a bit of a little condescendingly as to the outdated attribute of schooloral physics, sometimes not even suspecting how many magnets around us. In our apartment dozens of magnets: in the electric shaver, speakers, tape recorders, in hours, in jars with nails, finally. We ourselves are also magnets: biotoks current in us give birth around us the fancy pattern of magnetic power lines. Earth, on which we live, - a giant blue magnet. The sun is a yellow plasma ball - magazine more ambitious. Galaxies and nebulae, barely distinguished by telescopes, - incomprehensible size magnets. Thermonuclear synthesis, magnetodynamic generation of electricity, acceleration of charged particles in synchrotrons, raising sunken vessels - all areas where ambitious, unprecedented magnets are required. The problem of creating strong, supreme, ultrasive and even stronger magnetic fields has become one of the main most important physics and technique.

Magnet is known for a man of snow-shy times. We have reached us

about the magnets and their properties of Falez Mieta's tubes (approx. 600 BC) and Plato (427-347 Don.E.). The word "magnet" originated due to the fact that natural magnets Greeks were banned in Magnesia (Fessels).

Natural (or enlightened) magnets are found in nature as deposits of magnetic ores. Valtsky University is the largest known natural magnet. Its mass is 13 kg, and it is able to raise the cargo in 40 kg.

Artificial magnets are magnets created by a person based on various ferromagnetic. Taxable "powder" magnets (from iron, cobalt and some other files) can keep the load of more than 5,000 times greater than their own behavior.

Existing magnets of two different types:

Some - the so-called constricate manufactured from " magnetically solid »Materials. And magnetic properties are not associated with the use of external sources or currents.

The other type includes the so-called electromagnets with a core from " magnetically soft »Iron. The magnetic fields are created mainly by the fact that it takes an electric current on the wire covering the core.

In 1600, the Book of the Royal Doctor was published in London. Hilbert "About magnet, magnetic bodies and a large magnet-land." Etospication was the first idea of \u200b\u200bthe study of magnetic phenomena of science positions known to us. In this work, it was collected then information about magnetism electricities, as well as the results of the author's own experiments.

Of all, with a person who is annoyed, he first of all seeks to extract practical benefits. Unlinked this fate and magnet

In my work, I will try to trace how you are not used by a person not for war, but for peaceful purposes, including the applications in biology, medicine, in everyday life.

COMPASS,the device for determining horizontal directions on the terrain. It is applied to determine the direction in which the marine, airway, ground vehicle is moving; The directions in which pedestrian goes; directions on some object or landmark. Compassuses are divided into dynamic classes: magnetic compasses like shooter, which are used by the imaging and tourists, and non-magnetic, such as gyrocompass and radio compasses.

To 11 c. Referring to the Chinese Shen Kua and Chuu on the manufacture of compasses from natural immughs and using them in navigation. If

the long needle of the antholythomagnet is balanced on the axis, which allows it to turn freely in the horizontal address, then it is always facing one end to the north, and to the other - to the south. The setting pointing to the north, it is possible to use such a compass to the detection of directions.

Magnetic effects confused by the ends of such a needle, and therefore they were called poles (respectively northern and southern).

The main use is magnetic in electrical engineering, radiotechnics, instrument making, automation of ortho gear. Here ferromagnetic materials go on the manufacturer of junction, relays, etc.

In 1820, Earsted (1777-1851) discovered that the conductor runs on a magnetic arrow by turning it. Literally, the ampels showed that two parallel conductor with a current of one directed to each other. Later, he suggested that the unagnificent phenomena were due to currents, and the magnetic properties of permanent motors are associated with currents constantly circulating inside these magnets. Etopropement fully complies with modern ideas.

Electromachine Generos and Electric Motors -machinery type, converting either mechanical energy into electrical (generators), or electrical in mechanical (engines). Impellers are based on the principle of electromagnetic induction: in a wire moving in a magnetic field, an electromotive force (EMF) is guided. ActionElectrodic motors are based on the fact that the wire with a current, an inverse magnetic field is operating.

Magnetoelectrics.In such an appliance, the power of the magnetic field interaction with the current in the turns of the winding part, seeking to turn the last

Induction Power Energy. The induction is meant is nothing but a low-power electric motor transmitted current with two windings - current and voltage winding. Conductor placed between windings rotates under the action of torque proportional to power consumed. This moment is equalized by currents inscribed in the disk by a permanent magnet, so that the frequency of rotation of the discharge of power consumed.

Electric wristwatch Food miniature battery. For their work, much less details are booked than in the mechanical clock; Thus, there are two magnets, two coils and a transistor in the stem-electric portable clock.

Lock-mechanical, electrical or electronic device limiting the possibility of unauthorized use of anything. Castle can be driven by the device (key) available to the identified person, information (digital or letter code), introduced by an etyl person, or any individual characteristic (for example, drawings of the eye) of this person. The lock usually temporarily connects each other two nodes two parts in one device. Most often, the locks are mechanical, non-wider uses are electromagnetic locks.

Magnetic locks. Magnetic elements are applied by plindle locks of some models. The iconic lock is equipped with response codes of permanent magnets. When the correct key is inserted into the lock query, it attracts and installs the internal magnetic elements of the lock to the descriptive position, which allows you to open the lock.

Dynamometer -mechanical or electrical device for measurement of thrust or torque machine, machine or engine.

Brake dynamometersthere are the most visible constructions; These include, for example, brake penetration, hydraulic is electromagnetic brakes.

Electromagnetic dynamometer It can be filled in the form of a miniature device suitable for measuring characteristic-making engines.

Galvanometer-Content device for measuring weak currents. In the galvanometer, an ongoing moment that occurs in the interaction of a horseshoe-shaped constant, with a small cunning coil (weak electromagnet), suspended with a gap between the poles of the magnet. The torque, and consequently, the reel is proportional to the current and complete magnetic induction in the air transmission, so that the scale of the device with small deviations of the coil is almost linear. The use of its base is the most common type of appliances.

The spectrum of the manufactured devices is widely formulated: Devices panel direct and alternating current (magnetoelectric, magnetoelectric with rectifier and electromagnetic system), combined ampervoltmeter instruments, to diagnose the irregular equipment of the electrical equipment, measuring the temperature of flat surfaces, instruments for equipping school classrooms, testers IMSERTERS of all sorts of electrical parameters

Production abrasivesmall, solid, acute particles used in free or associated mechanical processing (including to give shape, sprinkles, grinding, polishing) a variety of materials and products of them (from largest plates to sheets of plywood, optical glasses and computer microcircuits ). Abrasives are natural or artificial. The effect of abrasives is reduced to the kudania of the material from the surface being processed. The production of the production of artificial abrasives of ferrosilicia, which is present, is settled on the bottom of the furnace, but its small amounts are being introduced into the abrasiveness of it is removed by a magnet.

Magnetic properties of the substance are widely used by Vnaughter and technology as a means of studying the structure of various bodies. So arose science:

Magnetochemistry (magnetochemistry) - section of physical chemistry, in which there is a connection between the magnetic and chemical properties of substances; In addition, the magnetochemistry explores the influence of magnetic fields into chemical processes. Magnitochemistry relies on modern magnetic phenomena physics. Studying communication magnetic and chemical properties allows us to find out the particular composition of the substance.

Magnetic flaw detector, Defective methods based on the study of the magnetic field distortion arising in places of defects in products from ferromagnetic materials.

. Supervice-frequency range technology

Ultrahigh Frequency Range (microwave) - frequency range of electromagnetic emission (100¸300 000 million Herz), located in the spectrum between ultravylovylovision frequencies and frequencies of far infrared region

Communication.Radio waves of the microwave range are widely shown in communication techniques. In addition to various military radio systems, in all countries of the world there are numerous commercial links of the microwave communication. Commonly, such radio waves do not follow the curvature of the earth's surface, as a rule, these lines, as a rule, consist of a reference stations installed on the tops of hills or on the radio worst Sinter of about 50 km.

Heat treatment of food products.The microwave radiation is for heat treatment of food products at home and in the dietary industry. The energy generated by powerful electronic lamps can be monitored in a small volume for highly efficient thermal processing products in the so-called. Microwave or microwave ovens, differing in cleanliness, silent and compactness. Such devices are applied on inlets, in railway restaurants and vending machines, quick preparation of products and cooking dishes are goggled. Industry is also a microwave oven for domestic purposes.

Fast progress in the field of microwave technology is largely festered with the invention of special electrovacuum devices - magnetron iris, capable of generating large amounts of microwave energy. The generator of the pretentious vacuum triode used at low frequencies in the microwave range is very ineffective.

Magnetron. In the Magnetron, invented in the United Kingdom, the Second World War, these disadvantages are missing, because the basis of a completely different approach to the generation of microwave radiation is the principle of volumetrozonator

In Magnetron, there are several volume resonators, symmetrically located around the cathode located in the center. Device placement poles strong magnet.

Running wave lamp (LBB).Another electionachamable device for generating and enhancing the electromagnetic VOLSVCH-band is a lamp of the running wave. It is a thin pumping tube inserted into the focusing magnetic coil.

Particle Accelerator, installation in which the directional beams of electrons, protons, ions and other charged faces with an energy significantly exceeding thermal energy is obtained using electrical and magnetic polynets.

In modern accelerators, numerous ways are used, incl. Powerful precision magnets.

In medical studies and diagnosticsthe officers play an important practical role. Throughout the world, many electronic linear accelerators generating intensive x-ray devices, used for tumor therapy, have at their disposal. To lesser extent used proteiclons or synchrotrons that generate proton beams. The advantage of protons of therapy of tumors in front of X-ray radiation is in the coolerocalyse energy release. Therefore, proton therapy is particularly effective in the treatment of brain and eye tumors, when damage to the surrounding healthy tissue to be as minimal.

Representatives of different sciences take into account the magnetic fields of all studies. The physicist measures the magnetic fields of atoms and elementary particles, the astronomer studies the role of space fields in the process of forming a new junction, the geologist for the magnetic field anomalies of the Earth finds the deposits of magnetic, from recently the biology also actively included in the study of the and use of magnets.

Biological sciencethe first half of the 20th century confidently described life functions, at all inconspicuous existence of any magnetic fields. Moreover, nosbiologists considered it necessary to emphasize that even a strong artificial magnetic field does not have any influence on biological objects.

In encyclopedias about the influence of the magnetic fields on biological processes, nothing was said. In the science of all over the world, single positive considerations of Other or other biological effects of magnetic fields appeared annually. However, this weak rod could melt the iceberg distrust even to the formulation of the problem itself ... and the stormy flow turned into a stormy stream. The avalanche of magnetobiological publications, as if having broken down from some vertices, from the beginning of the 60s it is constantly converted and swells skeptical statements.

From the alchemists of the XVIV and to the present day, the biological effect of the magnet many times is completely plans and critics. Repeatedly for several centuries, the surveillance and decline in interest in the medicinal action of the magnet. With it, they tried to try (and not unsuccessfully) nervous diseases, toothache, insomnia, stuff pain and in the stomach - hundreds of diseases.

For therapeutic purposes, the magnets is used, probably earlier than to determine the parties of the light.

As local outdoor and as amulet, the magnet enjoyed great success among the Chinese, Hindus, Egyptians, Arabs. Greeks, Romans, etc. The philosopher Aristotle and the historian of Pliny are about his medicinal properties.

In the second half of the XXVEK, magnetic bracelets are widely spread, which are beneficially influencing dummy with impaired blood pressure (hypertension and hypotension).

In addition to constant magnets, electromagnets are used. They are also used for a wide range of problems with science, technician, electronics, medicine (nervous diseases, diseases of the limbs, cardiovascular diseases, cancer diseases).

Most of all, scientists in the idea that magnetic fields increase the body's resistance.

There are electromagnetic measuring velocity of blood flow, miniature capsules, which can be moved along the blood vessels using external grunge fields to expand them, take samples at certain parts of the path or, on the contrary, locally output the various medicines.

The widespread method of removing metal particles from the eye.

Most of us know the heart of the heart using electrical sensors -Electrocardiogram. The electrical impulses produced by the heart, the creator of the heart of the heart, which in MAX values \u200b\u200bis 10-6 stress magnetic field of the Earth. The value of magnetocardiography is that it allows information about electrically "silent" regions of the heart.

It should be noted that biologises are asked to physicists to give the theory of the primary mechanism of the biological effect of the magnetic field, and physicists in response require more provenbiological facts from biologists. Obviously, there will be a successful cooperation between the public specialists.

An important link, uniting magnetobiological problems, is the reaction of the nervous system on magnet mention. It is the brain first that reacts to any changes in the external environment. It is that of his reactions will be the key to solving many problems of magnetobiology.

The easiest conclusion, which is one of the above - no area of \u200b\u200bapplied activity, where the magnets would not be used.

References:

1) BSE, the second edition, Moscow, 1957.

2) Colds Yu.A. "Man in Magnet Popeutina", "Knowledge", Moscow, 1972

3) Materials from the Internet - Encyclopedia

4) Putilov K.A. "Course of Physics", "Fizmatgiz", Moscow, 1964.