Electromagnetic field. Presentation on the topic "Magnetic phenomena in nature" Brazilian magnetic anomaly

Greetings, dear readers. Nature hides many secrets. Man managed to find explanations for some mysteries, but not for others. 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 experiments with this object, which has a magnetic field, from our school physics course.

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

Let's consider magnetic iron ore, from which the magnet is made. Each of you probably has such magnets on your refrigerator door.

You might be interested to know what other magnetic natural phenomena are there? From school physics lessons we know that fields can be magnetic and electromagnetic.

Let it be known to you that magnetic iron ore was known in living nature even before our era. At this time, a compass was created, which the Chinese emperor used during his numerous campaigns and just sea walks.

The word magnet is translated from Chinese as a loving stone. Amazing translation, isn't it?

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

The influence of the magnetic field in living 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 unmistakably. And the migrations of many animals depend on this field of earth.

So not only birds, 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 sense magnetic and electromagnetic fields.

But how exactly does any living creature living in wildlife, finds the desired landmark, scientists cannot answer unequivocally.

Magnetic storms and their impact on humans

We already know about the magnetic fields of our earth. 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 electrical energy that protects us. magnetic field land.

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

This magnetic phenomenon can last from an hour to 12 hours, or can be short-lived. And as noted by doctors, in to a greater extent This affects older people with cardiovascular diseases.

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

So, my dear readers, sometimes it’s 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 find out a little about them.

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

Scientists even today 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. It is unknown how the iron ore deposits were formed on the plain.

Brazilian magnetic anomaly

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

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

In addition, mysterious ones 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 would like to wish you good health and that unfavorable magnetic phenomena will bypass you!

I hope you liked 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. Let me say goodbye to you and see you again.

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In this lesson, the topic of which is “Electromagnetic field,” we will discuss the concept of “electromagnetic field,” the features of its manifestation and the parameters of this field.

We're talking on mobile phone. How is the signal transmitted? How is the signal transmitted from a space station flying to Mars? In the void? Yes, there may be no substance, but this is not emptiness, there is something else through which the signal is transmitted. This something was called an electromagnetic field. This is not a directly observable, but a really existing object of nature.

If a sound signal is a change in the parameters of a substance, for example air (Fig. 1), then a radio signal is a change in the parameters of the EM field.

Rice. 1. Sound wave propagation in air

The words “electric” and “magnetic” are clear to us, we have already studied separately electrical phenomena (Fig. 2) and magnetic phenomena (Fig. 3), but why then are we talking about the electromagnetic field? Today we will figure it out.

Rice. 2. Electric field

Rice. 3. Magnetic field

Examples of electromagnetic phenomena.

A microwave creates strong, and most importantly, very rapidly changing electromagnetic fields that act on an electric charge. And as we know, atoms and molecules of substances contain an electric charge (Fig. 4). This is where the electromagnetic field acts on it, forcing the molecules to move faster (Fig. 5) - the temperature increases and the food heats up. X-rays, ultraviolet rays, and visible light have the same nature.

Rice. 4. The water molecule is a dipole

Rice. 5. Movement of molecules having an electrical charge

In a microwave oven, the electromagnetic field imparts energy to the substance, which is used for heating, visible light imparts energy to the eye receptors, which is used to activate the receptor (Fig. 6), the energy of ultraviolet rays is used to form melanin in the skin (the appearance of tanning, Fig. 7), and The energy of X-rays causes the film to turn black, on which you can see an image of your skeleton (Fig. 8). The electromagnetic field in all these cases has different parameters, and therefore has different effects.

Rice. 6. Conditional diagram of activation of the eye receptor by visible light energy

Rice. 7. Skin tanning

Rice. 8. Blackening of the film during x-ray

So we encounter the electromagnetic field much more often than it seems, and have long been accustomed to the phenomena that are associated with it.

So, we know that the electric field arises around electric charges (Fig. 9). Everything is clear here.

Rice. 9. Electric field around an electric charge

If an electric charge moves, then, as we studied, a magnetic field arises around it (Fig. 10). Here the question already arises: an electric charge is moving, there is an electric field around it, what does the magnetic field have to do with it? One more question: we say “the charge is moving.” But motion is relative, and it can move in one frame of reference and be at rest in another (Fig. 11). Does this mean that a magnetic field will exist in one frame of reference, but not in another? But the field should not exist or not exist depending on the choice of reference frame.

Rice. 10. Magnetic field around a moving electric charge

Rice. 11. Relativity of charge motion

The fact is that there is a single electromagnetic field, and it has a single source - an electric charge. It has two components. Electric and magnetic fields are separate manifestations, separate components of a single electromagnetic field, which manifest themselves differently in different reference systems (Fig. 12).

Rice. 12. Manifestations of the electromagnetic field

You can choose a reference frame in which only the electric field, or only the magnetic field, or both at once will appear. However, it is impossible to choose a reference system in which both the electric and magnetic components will be zero, that is, in which the electromagnetic field will cease to exist.

Depending on the reference system, we see either one component of the field, or another, or both. It’s like the movement of a body in a circle: if you look at such a body from above, we will see movement along the circle (Fig. 13), if from the side, we will see oscillations along the segment (Fig. 14). In each projection onto the coordinate axis, circular motion is oscillations.

Rice. 13. Body movement in a circle

Rice. 14. Body oscillations along a segment

Rice. 15. Projection of circular movements onto the coordinate axis

Another analogy is the projection of a pyramid onto a plane. It can be projected into a triangle or a square. On the plane these are completely different figures, but all of this is a pyramid, which is looked at from different sides. But there is no angle from which the pyramid will disappear completely. It will just look more like a square or triangle (Fig. 16).

Rice. 16. Projections of a pyramid onto a plane

Consider a conductor carrying current. In it, negative charges are compensated by positive ones, the electric field around it is zero (Fig. 17). The magnetic field is not zero (Fig. 18); we considered the emergence of a magnetic field around a conductor with current. Let us choose a reference system in which the electrons forming electricity, will be motionless. But in this reference frame, the positively charged ions of the conductor will move in the opposite direction relative to the electrons: a magnetic field still arises (Fig. 18).

Rice. 17. A conductor with current whose electric field is zero

Rice. 18. Magnetic field around a current-carrying conductor

If electrons were in a vacuum, in this reference frame an electric field would arise around them, because they are not compensated by positive charges, but there would be no magnetic field (Fig. 19).

Rice. 19. Electric field around electrons in a vacuum

Let's look at another example. Let's take a permanent magnet. There is a magnetic field around it, but no electric one. Indeed, the electric field of protons and electrons is compensated (Fig. 20).

Rice. 20. Magnetic field around a permanent magnet

Let us take a reference frame in which the magnet is moving. A vortex electric field will appear around a moving permanent magnet (Fig. 21). How to identify it? Let us place a metal ring (immobile in this reference frame) in the path of the magnet. A current will arise in it - this is a well-known phenomenon of electromagnetic induction: when the magnetic flux changes, an electric field arises, leading to the movement of charges, to the appearance of a current (Fig. 22). In one reference frame there is no electric field, but in another it appears.

Rice. 21. Vortex electric field around a moving permanent magnet

Rice. 22. The phenomenon of electromagnetic induction

Magnetic field of a permanent magnet

In any substance, the electrons that revolve around the nucleus can be thought of as a small electric current that flows in a circle (Fig. 23). This means that a magnetic field arises around it. If the substance is not magnetic, it means that the planes of rotation of the electrons are directed arbitrarily and the magnetic fields from individual electrons compensate each other, since they are directed chaotically.

Rice. 23. Representation of the rotation of electrons around the nucleus

In magnetic substances, the planes of electron rotation are oriented approximately equally (Fig. 24). Therefore, the magnetic fields from all electrons add up, and a non-zero magnetic field is obtained on the scale of the entire magnet.

Rice. 24. Rotation of electrons in magnetic substances

There is a magnetic field around a permanent magnet, or rather the magnetic component of the electromagnetic field (Fig. 25). Can we find a frame of reference in which the magnetic component becomes zero and the magnet loses its properties? Still no. Indeed, electrons rotate in the same plane (see Fig. 24); at any moment in time, the speeds of the electrons are not directed in the same direction (Fig. 26). So it is impossible to find a frame of reference where they all freeze and the magnetic field disappears.

Rice. 25. Magnetic field around a permanent magnet

Thus, electric and magnetic fields are different manifestations of a single electromagnetic field. It cannot be said that at a specific point in space there is only a magnetic or only an electric field. There may be one or the other. It all depends on the frame of reference from which we view this point.

Why did we previously talk separately about electric and magnetic fields? Firstly, it happened historically: people have known about magnets for a long time, people have long observed fur electrified on amber, and no one realized that these phenomena were of the same nature. And secondly, this is a convenient model. In problems where we are not interested in the relationship between the electric and magnetic components, it is convenient to consider them separately. Two charges at rest in a given reference frame interact through an electric field - we apply Coulomb’s law to them, we are not interested in the fact that these same electrons can move in some reference frame and create a magnetic field, and we successfully solve the problem (Fig. 27) .

Rice. 27. Coulomb's Law

The effect of a magnetic field on a moving charge is considered in another model, and within the framework of its applicability, it also works perfectly in solving a number of problems (Fig. 28).

Rice. 28. Left hand rule

Let's try to understand how the components of the electromagnetic field are interconnected.

It is worth noting that the exact relationship is quite complex. It was developed by British physicist James Maxwell. He derived the famous 4 Maxwell equations (Fig. 29), which are studied in universities and require knowledge higher mathematics. We will not study them, of course, but in several in simple words Let's figure out what they mean.

Rice. 29. Maxwell's equations

Maxwell relied on the work of another physicist - Faraday (Fig. 30), who simply qualitatively described all the phenomena. He made drawings (Fig. 31) and notes that greatly helped Maxwell.

Rice. 31. Drawings by Michael Faraday from the book “Electricity” (1852)

Faraday discovered the phenomenon of electromagnetic induction (Fig. 32). Let's remember what it is. An alternating magnetic field generates an induced emf in a conductor. In other words, an alternating magnetic field (yes, in this case, not an electric charge) generates an electric field. This electric field is vortex, that is, its lines are closed (Fig. 33).

Rice. 32. Drawings by Michael Faraday for the experiment

Rice. 33. Occurrence of induced emf in a conductor

In addition, we know that a magnetic field is generated by a moving electric charge. It would be more correct to say that it is generated by an alternating electric field. As the charge moves, the electric field at each point changes, and this change generates a magnetic field (Fig. 34).

Rice. 34. Emergence of a magnetic field

You can notice the appearance of a magnetic field between the plates of the capacitor. When it charges or discharges, an alternating electric field is generated between the plates, which in turn generates a magnetic field. In this case, the magnetic field lines will lie in a plane perpendicular to the electric field lines (Fig. 35).

Rice. 35. The appearance of a magnetic field between the capacitor plates

Now let's look at Maxwell's equations (Fig. 29), a short explanation of them is given below for your reference.

The divergence icon is a mathematical operator; it highlights that component of the field that has a source, that is, the field lines begin and end at something. Look at the second equation: this component of the magnetic field is zero: magnetic field lines do not start or end at anything, there is no magnetic charge. Look at the first equation: this component of the electric field is proportional to the charge density. An electric field is created by an electric charge.

The most interesting are the following two equations. The rotor icon is a mathematical operator that highlights the vortex component of the field. The third equation means that the vortex electric field is created by a time-varying magnetic field (this is the derivative, which, as you know from mathematics, means the rate of change of the magnetic field). That is, we are talking about electromagnetic induction.

The fourth equation shows, if you do not pay attention to the proportionality coefficients: the vortex magnetic field is created by a changing electric field, as well as by an electric current ( - current density). We are talking about what we know well: a magnetic field is created by a moving electric charge and.

As you can see, an alternating magnetic field can generate an alternating electric field, and an alternating electric field, in turn, generates an alternating magnetic field, and so on (Fig. 36).

Rice. 36. An alternating magnetic field can generate an alternating electric field, and vice versa

As a result, space can form electromagnetic wave(Fig. 37). These waves have different manifestations - these are radio waves, visible light, ultraviolet and so on. We'll talk about this in the next lessons.

Rice. 37. Electromagnetic wave

Bibliography

1. Kasyanov V.A. Physics. 11th grade: Educational. for general education institutions. - M.: Bustard, 2005.
2. Myakishev G.Ya. Physics: Textbook. for 11th grade general education institutions. - M.: Education, 2010.

1. Internet portal “studopedia.su” ()
2. Internet portal “worldofschool.ru” ()

Homework

1. Is it possible to detect a magnetic field in a reference frame associated with one of the uniformly moving electrons in the flow that is created in the TV picture tube?
2. What field appears around an electron moving in a given frame of reference with constant speed?
3. What kind of field can be detected around motionless amber charged static electricity? Around a moving one? Justify your answers.

Physical bodies are the “actors” of physical phenomena. Let's get to know some of them.

Mechanical phenomena

Mechanical phenomena are the movement of bodies (Fig. 1.3) and their action on each other, for example repulsion or attraction. The action of bodies on each other is called interaction.

We will get to know mechanical phenomena in more detail this academic year.

Rice. 1.3. Examples of mechanical phenomena: movement and interaction of bodies during sports competitions (a, b. c); movement of the Earth around the Sun and its rotation around its own axis (g)

Sound phenomena

Sound phenomena, as the name suggests, are phenomena involving sound. These include, for example, the propagation of sound in air or water, as well as the reflection of sound from various obstacles - say, mountains or buildings. When sound is reflected, a familiar echo appears.

Thermal phenomena

Thermal phenomena are the heating and cooling of bodies, as well as, for example, evaporation (the transformation of liquid into vapor) and melting (the transformation solid into liquid).

Thermal phenomena are extremely widespread: for example, they determine the water cycle in nature (Fig. 1.4).

Rice. 1.4. Water cycle in nature

Heated sun rays the water of the oceans and seas evaporates. As the steam rises, it cools, turning into water droplets or ice crystals. They form clouds from which water returns to Earth in the form of rain or snow.

The real “laboratory” of thermal phenomena is the kitchen: whether soup is being cooked on the stove, whether water is boiling in a kettle, whether food is frozen in the refrigerator - all these are examples of thermal phenomena.

The operation of a car engine is also determined by thermal phenomena: when gasoline burns, a very hot gas is formed, which pushes the piston (motor part). And the movement of the piston is transmitted through special mechanisms to the wheels of the car.

Electrical and magnetic phenomena

The most striking (in the literal sense of the word) example of an electrical phenomenon is lightning (Fig. 1.5, a). Electric lighting and electric transport (Fig. 1.5, b) became possible thanks to the use of electrical phenomena. Examples of magnetic phenomena are the attraction of iron and steel objects by permanent magnets, as well as the interaction of permanent magnets.

Rice. 1.5. Electrical and magnetic phenomena and their uses

The compass needle (Fig. 1.5, c) rotates so that its “north” end points north precisely because the needle is a small permanent magnet, and the Earth is a huge magnet. The Northern Lights (Fig. 1.5, d) are caused by the fact that electrically charged particles flying from space interact with the Earth as with a magnet. Electrical and magnetic phenomena determine the operation of televisions and computers (Fig. 1.5, e, f).

Optical phenomena

Wherever we look, we will see optical phenomena everywhere (Fig. 1.6). These are phenomena associated with light.

An example of an optical phenomenon is the reflection of light various items. Rays of light reflected by objects enter our eyes, thanks to which we see these objects.

Rice. 1.6. Examples of optical phenomena: The sun emits light (a); The moon reflects sunlight (b); Mirrors (c) reflect light especially well; one of the most beautiful optical phenomena - rainbow (d)

Slide 2

Stages of work

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

Slide 3

Purpose: to experimentally study the properties of magnetic phenomena. Objectives: - Study literature. - Conduct experiments and observations.

Slide 4

Magnetism

Magnetism is a form of interaction of moving electric charges, carried out at a distance through a magnetic field. Magnetic interaction plays an important role in the processes occurring in the Universe. Here are two examples that confirm what has been said. 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 of cosmic rays. If it had not existed, the evolution of living beings on our planet would apparently have taken a different path, and perhaps life on Earth would not have arisen at all.

Slide 5

Slide 6

Earth's magnetic field

The main reason for the presence of the Earth's magnetic field is that the Earth's core consists of hot iron (a good conductor of electrical currents arising within 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 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 the Earth's.

Slide 7

Magnetic field change

The reason for the constant changes is the presence of mineral deposits. There are areas on Earth where its own magnetic field is greatly distorted by the occurrence of iron ores. For example, the Kursk magnetic anomaly, located in the Kursk region. The reason for 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 emitted by the Sun. The magnetic field of this flow interacts with the magnetic field of the Earth, and " magnetic storms".

Slide 8

Man and magnetic storms

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

Slide 9

Practical part

Goal: collect data on the number of ambulance calls for 2008 and draw a conclusion. To find out the correlation between childhood morbidity and magnetic storms.

1. 1. Magnetic phenomena Chernova Albina 8E
2. 2. 1.The Earth’s magnetic field (detected by the effect on the compass needle). The Earth's external magnetic field - the magnetosphere - extends in outer space to more than 20 Earth diameters and reliably protects our planet from a powerful flow of cosmic particles. The most striking manifestation of the magnetosphere are magnetic storms - rapid chaotic oscillations of all components of the geomagnetic field. Often, magnetic storms cover the entire globe: they are recorded by all magnetic observatories in the world - from Antarctica to Spitsbergen, and the type of magnetograms obtained at the most remote points of the Earth is surprisingly similar. Therefore, it is no coincidence that such magnetic storms are called global.
3. 3. 2. Permanent magnets (detected by their action on metal objects). There are two magnets different types. Some are so-called permanent magnets, made from “hard magnetic” materials. Their magnetic properties are not related to the use of external sources or currents. Another type includes the so-called electromagnets with a core made of “soft magnetic” iron. The magnetic fields they create are mainly due to the fact that an electric current passes through the wire of the winding surrounding the core. in engines - electromagnets - doorbell, telephone, telegraph...
4. 4. 3. Magnetic properties of substances (Antiferromagnets, Diamagnets, Paramagnets, Ferromagnetics, Ferrimagnetics - used in technology). 4. Alternating current generators (at nuclear power plants, state district power plants...). 5. Instruments of the magnetoelectric system (galvanometer - a sensitive device for measuring weak currents). 6. Transmission of information using electromagnetic waves. 7. Magnetic phenomena include magnetic induction, Ampere force, Lorentz force, electromagnetic induction. 8. Magnetic fluids, synthesized in the mid-20th century at the intersection of the sciences of colloid chemistry, physics of magnetic phenomena and hydrodynamics, belong to magnetically controlled materials and have received widespread practical use in mechanical engineering, medicine...
5. 5. Such magnetic phenomena are also known as: Magnetization of ferromagnetic materials Paramagnetic resonance Ferromagnetic resonance Antiferromagnetic resonance Phase transition to the ferromagnetic phase at the Curie temperature Phase transition to the antiferromagnetic phase at the Néel temperature. Movement of blast furnaces in an external magnetic field Spin waves Hysteresis of the magnetization reversal curve of ferromagnets Formation of a magnetic field during the movement of electric charges Resonance of domain walls in an alternating magnetic field Precession of the magnetic moment around the direction of the magnetic field Expulsion of diamagnets from a region of a strong magnetic field Retraction of paramagnetic materials into a region of a strong magnetic field Expulsion of a magnetic field fields from a superconductor