A thousand years before the first sightings electrical phenomena, mankind has already begun to accumulate knowledge of magnetism. And just four hundred years ago, when the formation of physics as a science had just begun, researchers separated magnetic properties substances from their electrical properties, and only after that they began to study them independently. This was how the experimental and theoretical foundation was laid, which by the middle of the 19th century became the foundation of e one theory of electrical and magnetic phenomena.

It seems that the unusual properties of magnetic iron ore were known as early as the Bronze Age in Mesopotamia. And after the beginning of the development of iron metallurgy, people noticed that it attracts iron products. The ancient Greek philosopher and mathematician Thales from the city of Miletus (640−546 BC) also thought about the reasons for this attraction, he explained this attraction by the animation of the mineral.

Greek thinkers imagined how invisible vapors envelop magnetite and iron, how these vapors attract substances to each other. Word "magnet" it could have been the name of the city of Magnesia-u-Sipila in Asia Minor, not far from which magnetite was deposited. One of the legends tells that the shepherd Magnis somehow ended up with his sheep next to a rock, which attracted the iron tip of his staff and boots.

In the ancient Chinese treatise "Spring and Autumn Records of Master Liu" (240 BC), the property of magnetite to attract iron is mentioned. A hundred years later, the Chinese noted that magnetite did not attract either copper or ceramics. In the 7th and 8th centuries, they noticed that a magnetized iron needle, being freely suspended, turns towards the North Star.

So by the second half of the 11th century, China began to manufacture marine compasses, which European sailors mastered only a hundred years after the Chinese. Then the Chinese had already discovered the ability of a magnetized needle to deviate in a direction east of the north, and thus discovered magnetic declination, ahead of European navigators in this, who came to exactly this conclusion only in the 15th century.

In Europe, the first properties of natural magnets were described by the French philosopher Pierre de Maricourt, who in 1269 served in the army of the Sicilian king Charles of Anjou. During the siege of one of the Italian cities, he sent a document to a friend in Picardy, which entered the history of science under the name “Letter on a Magnet”, where he spoke about his experiments with magnetic iron ore.

Marikur noted that in any piece of magnetite there are two areas that attract iron especially strongly. He noticed in this similarity with the poles celestial sphere, so I borrowed their names to designate areas of maximum magnetic force. From there, the tradition began to call the poles of magnets the south and north magnetic poles.

Marikur wrote that if you break any piece of magnetite into two parts, then each fragment will have its own poles.

Marikur first connected the effect of repulsion and attraction magnetic poles with the interaction of opposite (south and north), or the same poles. Maricourt is rightfully considered a pioneer of the European experimental scientific school, his notes on magnetism were reproduced in dozens of lists, and with the advent of printing they were published in the form of a brochure. They were cited by many learned naturalists up to the 17th century.

The English naturalist, scientist and physician William Gilbert was also well acquainted with Marikur's work. In 1600, he published On the Magnet, Magnetic Bodies, and the Great Magnet, the Earth. In this work, Hilbert gave all the information known at that time about the properties of natural magnetic materials and magnetized iron, and also described his own experiences with a magnetic ball, in which he reproduced the model of terrestrial magnetism.

In particular, he empirically established that at both poles of the "little Earth" the compass needle rotates perpendicular to its surface, it is set parallel at the equator, and rotates to an intermediate position at mid-latitudes. Thus Hilbert was able to model magnetic inclination, which was known in Europe for more than 50 years (in 1544 it was described by Georg Hartmann, a mechanic from Nuremberg).

Gilbert also reproduced the geomagnetic declination, which he attributed not to the ideally smooth surface of the ball, but on a planetary scale, explained this effect by attraction between continents. He discovered how strongly heated iron loses its magnetic properties, and when cooled, it restores them. Finally, Gilbert was the first to clearly distinguish between the attraction of a magnet and the attraction of amber rubbed with wool, which he called electrical force. It was a truly innovative work, appreciated by both contemporaries and descendants. Gilbert discovered that it would be correct to consider the Earth a "big magnet".

All the way early XIX century, the science of magnetism has advanced very little. In 1640, Benedetto Castelli, a student of Galileo, explained the attraction of magnetite by many very small magnetic particles included in its composition.

In 1778, Dutch-born Sebald Brugmans noticed how bismuth and antimony repelled the poles of a magnetic needle, the first example of a physical phenomenon that Faraday would later call diamagnetism.

Charles-Augustin Coulomb in 1785, through precise measurements on a torsion balance, proved that the force of interaction of magnetic poles with each other is inversely proportional to the square of the distance between the poles - just as exactly as the force of interaction electric charges.

Since 1813, the Danish physicist Oersted has been diligently trying to experimentally establish a connection between electricity and magnetism. The researcher used compasses as indicators, but for a long time he could not reach the goal, because he expected that the magnetic force was parallel to the current, and placed the electrical wire at right angles to the compass needle. The arrow did not react in any way to the occurrence of current.

In the spring of 1820, during one of his lectures, Oersted pulled a wire parallel to the arrow, and it is not clear what led him to this idea. And then the arrow swung. Oersted for some reason stopped the experiments for several months, after which he returned to them and realized that "the magnetic effect electric current directed along the circles embracing this current.

The conclusion was paradoxical, because before the rotating forces did not manifest themselves either in mechanics or anywhere else in physics. Oersted wrote an article where he outlined his conclusions, and did not study electromagnetism anymore.

In the autumn of the same year, the Frenchman Andre-Marie Ampère began experiments. First of all, repeating and confirming the results and conclusions of Oersted, in early October he discovered the attraction of conductors if the currents in them are directed in the same direction, and repulsion if the currents are opposite.

Ampere also studied the interaction between non-parallel current-carrying conductors, after which he described it with the formula, later called Ampère's law. The scientist also showed that current-carrying wires coiled into a spiral turn under the influence of a magnetic field, as happens with a compass needle.

Finally, he put forward the hypothesis of molecular currents, according to which, inside magnetized materials, there are continuous microscopic parallel to each other circular currents, causing magnetic action materials.

At the same time, Biot and Savard jointly bred mathematical form lu, which makes it possible to calculate the intensity of the magnetic field direct current.

And so, by the end of 1821, Michael Faraday, already working in London, made a device in which a conductor with current rotated around a magnet, and another magnet turned around another conductor.

Faraday suggested that both the magnet and the wire are wrapped in concentric lines of force, which cause their mechanical action.

Over time, Faraday became convinced of the physical reality of magnetic lines of force. By the end of the 1830s, the scientist was already clearly aware that energy as permanent magnets, and conductors with current, is distributed in the space surrounding them, which is filled with power magnetic lines. In August 1831, the researcher managed to force magnetism to produce the generation of electric current.

The device consisted of an iron ring with two opposite windings located on it. The first winding could be connected to an electric battery, and the second connected to a conductor placed above the magnetic compass needle. When a direct current flowed through the wire of the first coil, the needle did not change its position, but began to swing at the moments it was turned off and on.

Faraday came to the conclusion that at these moments, electrical impulses appeared in the wire of the second winding, associated with the disappearance or appearance of magnetic lines of force. He made the discovery that cause of the emerging electromotive force is the change in the magnetic field.

In November 1857, Faraday wrote a letter to Professor Maxwell in Scotland asking him to give a mathematical form to the knowledge of electromagnetism. Maxwell complied with the request. concept electromagnetic field found a place in 1864 in his memoirs.

Maxwell introduced the term "field" to denote the part of space that surrounds and contains bodies that are in a magnetic or electric state, and he emphasized that this space itself can be both empty and filled with absolutely any kind of matter, and the field will still have place.

In 1873, Maxwell published "Treatise on Electricity and Magnetism", where he presented a system of equations combining electromagnetic phenomena. He gave them a name general equations electromagnetic field, and to this day they are called Maxwell's equations. According to Maxwell's theory magnetism is a special kind of interaction between electric currents. It is the foundation on which all theoretical and experimental work relating to magnetism is built.

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Stages of work

Set goals and objectives Practical part. Research and observation. Conclusion.

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Purpose: to explore experimentally the properties of magnetic phenomena. Tasks: - To study the literature. - Conduct experiments and observations.

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Magnetism

Magnetism is a form of interaction between moving electric charges, carried out at a distance by means of a magnetic field. Magnetic interaction plays important role in the processes taking place in the universe. Here are two examples to prove this. It is known that the magnetic field of a star generates a stellar wind similar to the solar wind, which, by reducing the mass and moment of inertia of the star, changes the course of its development. It is also known that the Earth's magnetosphere protects us from the disastrous effects cosmic rays. If it were not for it, the evolution of living beings on our planet, apparently, would have gone a different way, and maybe life on Earth would not have arisen at all.

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Earth's magnetic field

The main reason for the presence of the Earth's magnetic field is that the Earth's core consists of red-hot iron (a good conductor of electrical currents that occur inside the Earth). Graphically, the Earth's magnetic field is similar to the magnetic field of a permanent magnet. The Earth's magnetic field forms a magnetosphere extending for 70-80 thousand km in the direction of the Sun. It shields the Earth's surface, protects against the harmful effects of charged particles, high energies and cosmic rays, and determines the nature of the weather. The Sun's magnetic field is 100 times greater than Earth's.

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Changing the magnetic field

The reason for the constant change is the presence of mineral deposits. There are territories on Earth where its own magnetic field is strongly distorted by the occurrence of iron ores. For example, the Kursk magnetic anomaly, located in the Kursk region. The cause of short-term changes in the Earth's magnetic field is the action of the "solar wind", i.e. the action of a stream of charged particles ejected by the Sun. The magnetic field of this stream interacts with the Earth's magnetic field, and "magnetic storms" arise.

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Man and magnetic storms

Cardio - vascular and circulatory system increases blood pressure, deteriorating coronary circulation. Magnetic storms cause exacerbations in the body of a person suffering from diseases of the cardiovascular system (myocardial infarction, stroke, hypertensive crisis, etc.). Respiratory organs magnetic storms biorhythms change. The condition of some patients worsens before magnetic storms, while others - after. The adaptability of such patients to the conditions of magnetic storms is very small.

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Practical part

Purpose: to collect data on the number of ambulance calls in 2008 and draw a conclusion. Find out the correlation between childhood morbidity and magnetic storms.

The nature of magnetism

Course 1 physical chemistry(under the editorship of Gerasimov Ya.I.) M .: Chemistry, 1969. T.1.

2. The course of physical chemistry (under the editorship of Krasnov K.S.) kn.1. M., Higher. school, 1995.

3. Brief reference book of physical and chemical quantities, ed. A.A. Ravdel and A.M. Ponomareva. L., Chemistry, 1983.

4. Rabinovich V.A., Khavin Z.Ya. Brief chemical reference book. L., Chemistry.

CHAPTER 1

PHYSICAL SUBSTANTIATION OF MAGNETIC

MEASUREMENTS

The nature of magnetism

The phenomenon of magnetism was discovered in antiquity as a field of permanent magnets. Long time magnetism like special form matter, was explained by the Coulomb model, which represents a set of charges of two signs. This discovery is still being used in science today. theoretical studies and developing conclusions. After the discovery by Oersted of the magnetic field of currents and subsequent studies by a number of other physicists, the complete equivalence of the properties of the magnetic fields of currents and magnets was established. According to the Ampère theorem, the magnetic field of a closed direct current can be considered as the field of a dipole consisting of magnetic charges positive and negative signs. Ampere suggested the appearance of electric molecular currents in the presence of magnets, which create a magnetic field. But these are not free macroscopic currents, but microscopic bound currents circulating within individual molecules of matter. Ampère's assumption was subsequently confirmed.

Any substance in nature is a magnet; it is capable of being magnetized under the influence of a magnetic field and acquiring its own magnetic moment. Magnets are substances that, when introduced into an external field, change in such a way that they themselves become sources of an additional magnetic field. A magnetized substance creates a magnetic field IN 1, which is superimposed on the primary field AT about. Both fields add up to the resulting field

B \u003d B o + B 1.(1.1)

Ampère explains the magnetization of bodies by the circulation of circular currents (molecular currents) in the molecules of matter. Currents have magnetic moments that create a magnetic field in the surrounding space. In the absence of an external field molecular currents are oriented randomly, as a result of which the resulting field due to them is equal to zero. The total magnetic moment of the body in this case is equal to zero. Under the action of an external magnetic field magnetic moments molecules acquire a predominant orientation in one direction, as a result of which the magnet is magnetized and its total moment becomes different from zero. The magnetic fields of individual molecular currents no longer compensate each other, and a field arises IN 1. This phenomenon was discovered experimentally by Faraday in 1845.

Molecules acquire magnetic properties due to the magnetic properties of their constituent atoms. It is known that an atom consists of a positive nucleus surrounded by negative electrons. An electron in orbit around the nucleus constant speed equivalent closed circuit orbital current J:

J=e¦ ,

where e– absolute value charge of an electron, ¦ is the frequency of its orbital revolution. Orbital magnetic moment R m electron is equal to

P m \u003d J S n,

where S is the area of ​​the orbit, n– unit vector normal to the plane of the orbit.

geometric sum orbital magnetic moments of all the electrons of an atom is called the orbital magnetic moment μ atom. In addition, it is known that the electron still has own moment an impulse that has nothing to do with its orbital movement. He acts like he's constantly spinning around own axis. This property is called the electron spin. The electron spin modulus depends on Planck's constant h:

Associated with this internal angular momentum is a magnetic moment of constant magnitude. The direction of this magnetic moment coincides with the direction expected for an electron if it is represented as a negatively charged ball rotating around an axis. The value of the spin magnetic moment is always the same, the external field can only affect its direction.

If the spin moments of an electron can be freely oriented in matter, then we can expect that they will easily be located in the direction of the applied field AT, i.e. will choose the direction of energy. We can assume that the magnetic properties of a substance depend on the applied induced field.

The composition of the nuclei of atoms various elements also includes protons. Their number in the nucleus corresponds to serial number element in periodic system D.I. Mendeleev. The proton has a positive electric charge numerically equal to the charge of the electron. The mass of a proton is 1836.5 times the mass of an electron. In the classical model, the proton is represented as a mass that carries a positive charge and rotates around its own axis. The proton is represented as an elementary rotating mass, which has an angular momentum due to rotation around its own axis. The rotation of a proton carrying an electric charge creates a ring current, which, in turn, causes a magnetic moment called its own magnetic moment, or the spin magnetic moment of the proton.

Motion elementary particles an atom of matter in a magnetic field creates a net magnetic effect, which is quantitative characteristic magnetized state of matter. This vector quantity is called magnetization, it is equal to the ratio of the magnetic moment of a macroscopically small volume of matter υ to the value of this volume:

J= , (1.2)

where is the magnetic moment of the atom contained in the volume υ . In other words, the magnetization is bulk density magnetic moment of a magnet.

A substance that contains an evenly distributed throughout its volume a large number of identically directed atomic magnetic dipoles, is called uniformly magnetized. Magnetization vector J is the product of the number of oriented dipoles per unit volume and the magnetic moment μ each dipole.

Rice. 1.1. Magnetic field around a magnetized cylinder

Consider experimental studies. The magnetic field near a magnetized rod, such as a compass needle, is very similar to the electric field of an electrically polarized rod, which has an excess positive charges at one end and an excess of negative charges at the other. We get that the magnetic field has its own sources, which are associated with it in the same way as an electric charge is associated with electric field. One magnetic charge can be called north pole and the other to the south.

On fig. Figure 1.1 shows the magnetic field around a magnetized cylinder, as seen from the orientation of small pieces of nickel wire immersed in glycerin. The studies were carried out at the Palmer Physical Laboratory Princeton University(E. Purcell) /21/. Experience shows that it was not possible to obtain an excess of isolated magnetic charges of the same sign, but, on the contrary, confirms that charges exist in pairs and there is a connection between them. The researchers claim that ordinary matter is "made" of electrical charges, not magnetic ones.

It can be concluded that the source of the magnetic field are electric currents. This confirms Ampère's idea that magnetism can be explained by the existence of many tiny rings of electric current distributed throughout matter.

The nature of magnetic phenomena

All substances, without exception, react when an external magnetic field is applied. If we consider the electron orbit as a circuit with a current, then when a magnetic field is applied, in accordance with the Lenz rule, an emf should be induced, which in turn will create a magnetic field directed against the external one. Therefore, inside the material, the magnetic field strength will decrease. Its relative decrease - diamagnetic susceptibility - is about 10 -8 . All substances possess diamagnetism, and its magnitude is almost independent of temperature.

In addition to the magnetic moment that arises due to the movement of an electron in orbit, an electron, having its own spin moment of momentum, has a spin magnetic moment. Therefore, in general case an atom of a substance can have its own net magnetic moment. In the absence of a magnetic field, the magnetic moment of the body is zero due to the random distribution of atomic magnetic moments. The action of the magnetic field will be reduced to the orientation of the magnetic moments of the atoms in the direction of the applied field, and inside the material the magnetic field strength will increase - the paramagnetic effect.

Paramagnetism, like diamagnetism, is a relatively weak effect, and substances in which only these effects take place are called weak magnets (). When the field is removed, both effects are eliminated. The temperature dependence of the paramagnetic effect is described by the Curie-Weiss law:

where and Θ p are constants and is the paramagnetic susceptibility.

Substances possessing a magnetically ordered state (ferromagnets, antiferromagnets, and ferrimagnets) sharply differ from dia- and paramagnets in their response to an external magnetic field. These are substances in which, regardless of the external field, the magnetic moments of the electron spins line up parallel to each other (ferromagnetism) or antiparallel (antiferromagnetism). The magnetically ordered state has a quantum mechanical nature. Probabilistic definition the location of the "wave-particle" of the electron, given quantum mechanics, made it possible to understand what causes the magnetic moments to line up in parallel - this is the so-called energy of the exchange interaction. We can say that this is the electrostatic energy of the interaction of two electrons, when the first electron is in place of the second, and the second in place of the first. The likelihood of such a situation in quantum mechanics is not equal to zero. At certain distance between interacting atoms, the energy of the exchange interaction will be minimal if the magnetic moments of the spins are parallel (ferromagnetism) or antiparallel (antiferromagnetism).

So, the ordered alignment of the magnetic moments of the spins of electrons is the result of the interaction of electrons. The question arises, what direction will the magnetic moments of the spins in crystal lattice? In this case, it is necessary to take into account the spatial arrangement of the electron orbit in the crystal lattice. The interaction between the magnetic moments of the orbits and the magnetic moments of the spins comes into force. This interaction, denoted as the energy of magnetic crystallographic anisotropy, determines the direction in which the magnetic moments of the spins line up. Magnetic crystal anisotropy (difference in directions) of spontaneous magnetization in the crystal lattice occurs. For iron, for example, the direction in which the magnetic moments line up is the edge of the unit cell cube.

Greetings dear readers. Nature hides many secrets in itself. Some of the mysteries man managed to find explanations, while others did not. Magnetic phenomena in nature occur on our earth and around us, and sometimes we simply do not notice them.

One of these phenomena can be seen by picking up a magnet and pointing it at a metal nail or pin. See how they are attracted to each other.

Many of us still remember school course physics experiments with this subject, which has a magnetic field.

I hope you remembered what magnetic phenomena are? Of course, this is the ability to attract other metal objects to itself, having a magnetic field.

Consider the magnetic iron ore from which the magnet is made. Each of you probably has such magnets on the refrigerator door.

You will probably be interested to know what other magnetic natural phenomena? From school lessons in physics we know that fields are magnetic and electromagnetic.

May you know that magnetic iron ore in wildlife was known even before our era. At this time, the compass was created, which chinese emperor used during his many trips and just boat trips.

Translated from Chinese the word magnet is like a loving stone. Amazing translation, isn't it?

Christopher Columbus, using a magnetic compass in his travels, noticed that geographical coordinates influence the deviation of the needle in the compass. Subsequently, this result of observation led scientists to the conclusion that there are magnetic fields on the earth.

The influence of the magnetic field in animate and inanimate nature

The unique ability of migratory birds to accurately locate their habitats has always been of interest to scientists. The earth's magnetic field helps them lay unerringly. Yes, and the migration of many a number of animals depend on this field of the earth.

So not only birds have their “magnetic cards”, but also such animals as:

• Turtles
• Sea shellfish
• salmon fish
• salamanders
• and many other animals.

Scientists have found that in the body of living organisms there are special receptors, as well as magnetite particles, which help to feel magnetic and electromagnetic fields.

But just how any creature living in wild nature, finds the desired landmark, scientists cannot unambiguously answer.

Magnetic storms and their impact on humans

We already know about magnetic fields our land. They protect us from the effects of charged microparticles that reach us from the Sun. A magnetic storm is nothing more than a sudden change in the earth's electromagnetic field protecting us.

Have you noticed how sometimes a sudden sharp pain shoots into your head temple and then a severe headache appears? All these painful symptoms that occur in the human body indicate the presence of this natural phenomenon.

This magnetic phenomenon can last from an hour to 12 hours, and may be short-lived. And as noted by doctors, in more older people with cardiovascular diseases suffer from this.

It has been noted that the number of heart attacks increases during a prolonged magnetic storm. There are a number of scientists who track the appearance of magnetic storms.

So my dear readers, it is sometimes worth learning about their appearance and trying to prevent their terrible consequences if possible.

Magnetic anomalies in Russia

Throughout the vast territory of our earth there are various kinds of magnetic anomalies. Let's learn a little about them.

The famous scientist and astronomer P. B. Inokhodtsev, back in 1773, studied geographical position all cities of the central part of Russia. It was then that he discovered a strong anomaly in the region of Kursk and Belgorod, where the compass needle was feverishly spinning. And only in 1923 the first well was drilled, which revealed metal ore.

Even today, scientists cannot explain the huge accumulations of iron ore in the Kursk magnetic anomaly.

We know from geography textbooks that all iron ore is mined in mountainous areas. And how deposits of iron ore were formed on the plain is unknown.

Brazilian magnetic anomaly

Off the ocean coast of Brazil at an altitude of more than 1000 kilometers, the bulk of the instruments flying over this place aircraft- aircraft and even satellites suspend their work.

Imagine an orange orange. Its peel protects the pulp, and the magnetic field of the earth with protective layer atmosphere protects our planet from harmful effects from space. And the Brazilian anomaly is like a dent in that skin.

In addition, the mysterious were observed more than once in this unusual place.

There are still many mysteries and secrets of our land to be revealed to scientists, my friends. I want to wish you good health and that adverse magnetic phenomena bypass you!

I hope you like mine short review magnetic phenomena in nature. Or maybe you have already observed them or felt their effect on yourself. Write about it in your comments, I will be interested to read about it. And that's all for today. Allow me to say goodbye and see you again.

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