What is a magnetic field and its properties. What is a magnetic field and where does it come from?

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A magnetic field can be created by the current of charged particles and/or the magnetic moments of electrons in atoms (and the magnetic moments of other particles, although to a noticeably lesser extent) (permanent magnets).

In addition, it appears in the presence of a time-varying electric field.

Main power characteristic magnetic field is magnetic induction vector (magnetic field induction vector). From a mathematical point of view, it is a vector field, which defines and specifies the physical concept of a magnetic field. Often, for brevity, the magnetic induction vector is simply called a magnetic field (although this is probably not the most strict use of the term).

Another fundamental characteristic of the magnetic field (alternative to magnetic induction and closely interrelated with it, almost equal to it in physical value) is vector potential .

A magnetic field can be called a special type of matter, through which interaction occurs between moving charged particles or bodies with a magnetic moment.

Magnetic fields are a necessary (in the context) consequence of the existence of electric fields.

From the point of view of quantum field theory, magnetic interaction is how special case electromagnetic interaction is carried by a fundamental massless boson - a photon (a particle that can be represented as a quantum excitation electromagnetic field), often (for example, in all cases of static fields) - virtual.

Magnetic field sources

A magnetic field is created (generated) by a current of charged particles, or a time-varying electric field, or the particles’ own magnetic moments (the latter, for the sake of uniformity of the picture, can be formally reduced to electric currents).

Calculation

In simple cases, the magnetic field of a conductor with current (including the case of a current distributed arbitrarily over a volume or space) can be found from the Biot-Savart-Laplace law or the circulation theorem (also known as Ampere’s law). In principle, this method is limited to the case (approximation) of magnetostatics - that is, the case of constant (if we are talking about strict applicability) or rather slowly changing (if we are talking about approximate application) magnetic and electric fields.

In more complex situations it is sought as a solution to Maxwell's equations.

Manifestation of magnetic field

The magnetic field manifests itself in the effect on the magnetic moments of particles and bodies, on moving charged particles (or current-carrying conductors). The force acting on an electrically charged particle moving in a magnetic field is called the Lorentz force, which is always directed perpendicular to the vectors v And B. It is proportional to the charge of the particle q, speed component v, perpendicular to the direction of the magnetic field vector B, and the magnitude of the magnetic field induction B. In the SI system of units, the Lorentz force is expressed as follows:

in the GHS unit system:

where square brackets denote the vector product.

Also (due to the action of the Lorentz force on charged particles moving along a conductor), a magnetic field acts on a conductor with current. The force acting on a current-carrying conductor is called Ampere force. This force consists of the forces acting on individual charges moving inside the conductor.

Interaction of two magnets

One of the most common in ordinary life manifestations of a magnetic field - the interaction of two magnets: like poles repel, opposite poles attract. It is tempting to describe the interaction between magnets as the interaction between two monopoles, and from a formal point of view this idea is quite feasible and often very convenient, and therefore practically useful (in calculations); however, detailed analysis shows that this is in fact not a completely correct description of the phenomenon (the most obvious question that cannot be explained within such a model is the question of why monopoles can never be separated, that is, why experiment shows that no isolated the body does not actually have a magnetic charge; in addition, the weakness of the model is that it is not applicable to the magnetic field created by a macroscopic current, which means, if not considered as a purely formal device, it only leads to a complication of the theory in a fundamental sense).

It would be more correct to say that a magnetic dipole placed in a non-uniform field is acted upon by a force that tends to rotate it so that the magnetic moment of the dipole is aligned with the magnetic field. But no magnet experiences the (total) force exerted by a uniform magnetic field. Force acting on a magnetic dipole with a magnetic moment m expressed by the formula:

The force acting on a magnet (which is not a single point dipole) from a non-uniform magnetic field can be determined by summing all the forces (determined by this formula) acting on the elementary dipoles that make up the magnet.

However, an approach is possible that reduces the interaction of magnets to the Ampere force, and the formula itself above for the force acting on a magnetic dipole can also be obtained based on the Ampere force.

The phenomenon of electromagnetic induction

Vector field H measured in amperes per meter (A/m) in the SI system and in oersteds in the GHS. Oersteds and Gaussians are identical quantities; their division is purely terminological.

Magnetic field energy

The increment in magnetic field energy density is equal to:

H- magnetic field strength, B- magnetic induction

In the linear tensor approximation, magnetic permeability is a tensor (we denote it) and multiplication of a vector by it is tensor (matrix) multiplication:

or in components.

The energy density in this approximation is equal to:

- components of the magnetic permeability tensor, - tensor, represented by a matrix inverse to the matrix of the magnetic permeability tensor, - magnetic constant

When choosing coordinate axes that coincide with the main axes of the magnetic permeability tensor, the formulas in the components are simplified:

- diagonal components of the magnetic permeability tensor in its own axes (the remaining components in these special coordinates - and only in them! - are equal to zero).

In an isotropic linear magnet:

- relative magnetic permeability

In a vacuum and:

The energy of the magnetic field in the inductor can be found using the formula:

Ф - magnetic flux, I - current, L - inductance of a coil or turn with current.

Magnetic properties of substances

From a fundamental point of view, as stated above, a magnetic field can be created (and therefore - in the context of this paragraph - weakened or strengthened) by an alternating electric field, electric currents in the form of streams of charged particles, or magnetic moments of particles.

The specific microscopic structure and properties of various substances (as well as their mixtures, alloys, states of aggregation, crystalline modifications, etc.) lead to the fact that at the macroscopic level they can behave quite differently under the influence of an external magnetic field (in particular, weakening or enhancing it to varying degrees).

In this regard, substances (and environments in general) with respect to their magnetic properties are divided into the following main groups:

Antiferromagnets are substances in which an antiferromagnetic order has been established for the magnetic moments of atoms or ions: the magnetic moments of substances are directed oppositely and are equal in strength.
Diamagnets are substances that are magnetized against the direction of an external magnetic field.
Paramagnetic substances are substances that are magnetized in an external magnetic field in the direction of the external magnetic field.
Ferromagnets are substances in which, below a certain critical temperature (Curie point), a long-range ferromagnetic order of magnetic moments is established
Ferrimagnets are materials in which the magnetic moments of the substance are directed in opposite directions and are not equal in strength.
The groups of substances listed above mainly include ordinary solid or (some) liquid substances, as well as gases. The interaction with the magnetic field of superconductors and plasma is significantly different.

Toki Fuko

Foucault currents (eddy currents) are closed electric currents in a massive conductor that arise when the magnetic flux penetrating it changes. They are induced currents formed in a conducting body either as a result of a change in time of the magnetic field in which it is located, or as a result of the movement of the body in a magnetic field, leading to a change in the magnetic flux through the body or any part of it. According to Lenz's rule, the magnetic field of Foucault currents is directed so as to counteract the change in magnetic flux that induces these currents.

History of the development of ideas about the magnetic field

Although magnets and magnetism were known much earlier, the study of the magnetic field began in 1269, when the French scientist Peter Peregrine (Knight Pierre of Mericourt) marked the magnetic field on the surface of a spherical magnet using steel needles and determined that the resulting magnetic field lines intersected at two points, which he called “poles” by analogy with the poles of the Earth. Nearly three centuries later, William Gilbert Colchester used the work of Peter Peregrinus and for the first time definitively stated that the Earth itself was a magnet. Published in 1600, Gilbert's work "De Magnete", laid the foundations of magnetism as a science.

Three discoveries in a row challenged this “basis of magnetism.” First, in 1819, Hans Christian Oersted discovered that electric current creates a magnetic field around itself. Then, in 1820, André-Marie Ampère showed that parallel wires carrying current in the same direction attract each other. Finally, Jean-Baptiste Biot and Félix Savart discovered a law in 1820, called the Biot-Savart-Laplace law, which correctly predicted the magnetic field around any live wire.

Expanding on these experiments, Ampère published his own successful model of magnetism in 1825. In it, he showed the equivalence of electric current in magnets, and instead of the dipoles of magnetic charges of the Poisson model, he proposed the idea that magnetism is associated with constantly flowing current loops. This idea explained why magnetic charge could not be isolated. In addition, Ampere derived the law named after him, which, like the Biot-Savart-Laplace law, correctly described the magnetic field created by direct current, and also introduced the magnetic field circulation theorem. Also in this work, Ampère coined the term "electrodynamics" to describe the relationship between electricity and magnetism.

Although the strength of the magnetic field of a moving electric charge implied in Ampere's law was not explicitly stated, Hendrik Lorentz derived it from Maxwell's equations in 1892. Wherein classical theory electrodynamics was basically completed.

The twentieth century expanded views on electrodynamics, thanks to the emergence of the theory of relativity and quantum mechanics. Albert Einstein, in his 1905 paper establishing his theory of relativity, showed that electric and magnetic fields are part of the same phenomenon, viewed in different frames of reference. (See Moving Magnet and the Conductor Problem—a thought experiment that ultimately helped Einstein develop special relativity). Finally, quantum mechanics was combined with electrodynamics to form quantum electrodynamics (QED).

Notes

TSB. 1973, "Soviet Encyclopedia".
In particular cases, a magnetic field can exist in the absence of an electric field, but generally speaking, a magnetic field is deeply interconnected with an electric one, both dynamically (the mutual generation of variables by the electric and magnetic fields of each other), and in the sense that upon transition to a new reference system, the magnetic field and the electric field are expressed through each other, that is, generally speaking they cannot be unconditionally separated.
Yavorsky B. M., Detlaf A. A. Handbook of Physics: 2nd ed., revised. - M.: Nauka, Main editorial office of physical and mathematical literature, 1985, - 512 p.
In the SI, magnetic induction is measured in tesla (T), in the CGS system in gauss.
They coincide exactly in the CGS system of units, in SI they differ by a constant coefficient, which, of course, does not change the fact of their practical physical identity.
The most important and obvious difference here is that the force acting on a moving particle (or on a magnetic dipole) is calculated precisely through and not through . Any other physically correct and meaningful measurement method will also make it possible to measure precisely, although for formal calculations it sometimes turns out to be more convenient - which, in fact, is the point of introducing this auxiliary quantity (otherwise one would do without it altogether, using only
However, we must understand well that a number of fundamental properties of this “matter” are fundamentally different from the properties of that normal looking"matter", which could be designated by the term "substance".
See Ampere's theorem.
For a uniform field, this expression gives zero force, since all derivatives are equal to zero B by coordinates.
Sivukhin D.V. General course physics. - Ed. 4th, stereotypical. - M.: Fizmatlit; Publishing house MIPT, 2004. - T. III. Electricity. - 656 s. - ISBN 5-9221-0227-3; ISBN 5-89155-086-5.

The magnetic field has long raised many questions in humans, but even now remains a little-known phenomenon. Many scientists tried to study its characteristics and properties, because the benefits and potential of using the field were undeniable facts.

Let's look at everything in order. So, how does any magnetic field operate and form? That's right, from electric current. And current, according to physics textbooks, is a directional flow of charged particles, isn’t it? So, when a current passes through any conductor, a certain type of matter begins to act around it - a magnetic field. A magnetic field can be created by a current of charged particles or by the magnetic moments of electrons in atoms. Now this field and matter have energy, we see it in electromagnetic forces that can affect the current and its charges. The magnetic field begins to influence the flow of charged particles, and they change the initial direction of movement perpendicular to the field itself.

A magnetic field can also be called electrodynamic, because it is formed near moving particles and affects only moving particles. Well, it is dynamic due to the fact that it has a special structure in rotating bions in a region of space. An ordinary moving electric charge can make them rotate and move. Bions transmit any possible interactions in this region of space. Therefore, a moving charge attracts one pole of all bions and makes them rotate. Only he can bring them out of their state of rest, nothing else, because other forces will not be able to influence them.

In an electric field there are charged particles that move very quickly and can travel 300,000 km in just a second. Light has the same speed. A magnetic field cannot exist without an electric charge. This means that the particles are incredibly closely related to each other and exist in a common electromagnetic field. That is, if there are any changes in the magnetic field, then there will be changes in the electric one. This law is also reverse.

We talk a lot about the magnetic field here, but how can we imagine it? We cannot see it with our human naked eye. Moreover, due to the incredibly fast propagation of the field, we do not have time to detect it using various devices. But in order to study something, you need to have at least some idea about it. It is also often necessary to depict a magnetic field in diagrams. To make it easier to understand, conditional field lines are drawn. Where did they get them from? They were invented for a reason.

Let's try to see the magnetic field using small metal filings and an ordinary magnet. Let's pour these sawdust onto a flat surface and expose them to a magnetic field. Then we will see that they will move, rotate and line up in a pattern or pattern. The resulting image will show the approximate effect of forces in the magnetic field. All forces and, accordingly, lines of force are continuous and closed in this place.

A magnetic needle has similar characteristics and properties to a compass, and is used to determine the direction of lines of force. If it falls into the zone of action of a magnetic field, we can see the direction of action of the forces from its north pole. Then let us highlight several conclusions from here: the top of an ordinary permanent magnet, from which the lines of force emanate, is designated the north pole of the magnet. Whereas south pole indicate the point where the forces are closed. Well, the lines of force inside the magnet are not highlighted in the diagram.

The magnetic field, its properties and characteristics have a fairly wide application, because in many problems it has to be taken into account and studied. This is the most important phenomenon in the science of physics. More complex things such as magnetic permeability and induction are inextricably linked with it. To explain all the reasons for the appearance of a magnetic field, we must rely on real scientific facts and confirmations. Otherwise in more complex tasks the wrong approach can destroy the integrity of the theory.

Now let's give examples. We all know our planet. Will you say that it has no magnetic field? You may be right, but scientists say that processes and interactions inside the Earth's core give rise to a huge magnetic field that stretches for thousands of kilometers. But in any magnetic field there must be its poles. And they exist, they are just located a little away from the geographic pole. How do we feel it? For example, birds have developed navigation abilities, and they navigate, in particular, by the magnetic field. So, with his help, the geese arrive safely in Lapland. Special navigation devices also use this phenomenon.

Just as a stationary electric charge acts on another charge through an electric field, an electric current acts on another current through magnetic field. The effect of a magnetic field on permanent magnets is reduced to its effect on charges moving in the atoms of a substance and creating microscopic circular currents.

The doctrine of electromagnetism based on two provisions:

the magnetic field acts on moving charges and currents;
a magnetic field arises around currents and moving charges.

Magnet interaction

Permanent magnet(or magnetic needle) is oriented along the Earth's magnetic meridian. The end that points north is called north pole(N), and the opposite end is south pole(S). Bringing two magnets closer to each other, we note that their like poles repel, and their unlike poles attract ( rice. 1 ).

If we separate the poles by cutting a permanent magnet into two parts, we will find that each of them will also have two poles, i.e. will be a permanent magnet ( rice. 2 ). Both poles - north and south - are inseparable from each other and have equal rights.

The magnetic field created by the Earth or permanent magnets is represented, like an electric field, by magnetic lines of force. A picture of the magnetic field lines of a magnet can be obtained by placing a sheet of paper over it, on which iron filings are sprinkled in an even layer. When exposed to a magnetic field, the sawdust becomes magnetized - each of them has north and south poles. The opposite poles tend to move closer to each other, but this is prevented by the friction of the sawdust on the paper. If you tap the paper with your finger, the friction will decrease and the filings will be attracted to each other, forming chains depicting magnetic field lines.

On rice. 3 shows the location of sawdust and small magnetic arrows in the field of a direct magnet, indicating the direction of the magnetic field lines. This direction is taken to be the direction of the north pole of the magnetic needle.

Oersted's experience. Magnetic field of current

IN early XIX V. Danish scientist Ørsted made an important discovery when he discovered action of electric current on permanent magnets . He placed a long wire near a magnetic needle. When current was passed through the wire, the arrow rotated, trying to position itself perpendicular to it ( rice. 4 ). This could be explained by the emergence of a magnetic field around the conductor.

The magnetic field lines created by a straight conductor carrying current are concentric circles located in a plane perpendicular to it, with centers at the point through which the current passes ( rice. 5 ). The direction of the lines is determined by the right screw rule:

If the screw is rotated in the direction of the field lines, it will move in the direction of the current in the conductor .

The strength characteristic of the magnetic field is magnetic induction vector B . At each point it is directed tangentially to the field line. Electric field lines begin on positive charges and end on negative ones, and the force acting on the charge in this field is directed tangentially to the line at each point. Unlike the electric field, the magnetic field lines are closed, which is due to the absence of “magnetic charges” in nature.

The magnetic field of a current is fundamentally no different from the field created by a permanent magnet. In this sense, an analogue of a flat magnet is a long solenoid - a coil of wire, the length of which is significantly greater than its diameter. The diagram of the lines of the magnetic field created by him, shown in rice. 6 , is similar to that for a flat magnet ( rice. 3 ). The circles indicate the cross sections of the wire forming the solenoid winding. Currents flowing through the wire away from the observer are indicated by crosses, and currents in the opposite direction - towards the observer - are indicated by dots. The same notations are accepted for magnetic field lines when they are perpendicular to the drawing plane ( rice. 7 a, b).

The direction of the current in the solenoid winding and the direction of the magnetic field lines inside it are also related by the rule of the right screw, which in this case is formulated as follows:

If you look along the axis of the solenoid, the current flowing in a clockwise direction creates a magnetic field in it, the direction of which coincides with the direction of movement of the right screw ( rice. 8 )

Based on this rule, it is easy to understand that the solenoid shown in rice. 6 , the north pole is its right end, and the south pole is its left.

The magnetic field inside the solenoid is uniform - the magnetic induction vector has a constant value there (B = const). In this respect, the solenoid is similar to a parallel-plate capacitor, within which a uniform electric field is created.

Force acting in a magnetic field on a current-carrying conductor

It was experimentally established that a force acts on a current-carrying conductor in a magnetic field. In a uniform field, a straight conductor of length l, through which a current I flows, located perpendicular to the field vector B, experiences the force: F = I l B .

The direction of the force is determined left hand rule:

If the four outstretched fingers of the left hand are placed in the direction of the current in the conductor, and the palm is perpendicular to vector B, then the outstretched thumb indicates the direction of the force acting on the conductor (rice. 9 ).

It should be noted that the force acting on a conductor with current in a magnetic field is not directed tangentially to its lines of force, like an electric force, but perpendicular to them. A conductor located along the lines of force is not affected by magnetic force.

The equation F = IlB lets give quantitative characteristics magnetic field induction.

Attitude does not depend on the properties of the conductor and characterizes the magnetic field itself.

The magnitude of the magnetic induction vector B is numerically equal to the force acting on a conductor located perpendicular to it unit length, through which a current of one ampere flows.

In the SI system, the unit of magnetic field induction is the tesla (T):

A magnetic field. Tables, diagrams, formulas

(Interaction of magnets, Oersted's experiment, magnetic induction vector, vector direction, superposition principle. Graphic image magnetic fields, magnetic induction lines. Magnetic flux, energy characteristics of the field. Magnetic forces, Ampere force, Lorentz force. Movement of charged particles in a magnetic field. Magnetic properties of matter, Ampere's hypothesis)

Magnetic field and its characteristics. When an electric current passes through a conductor, a a magnetic field. A magnetic field represents one of the types of matter. It has energy, which manifests itself in the form of electromagnetic forces acting on individual moving electric charges (electrons and ions) and on their flows, i.e. electric current. Under the influence of electromagnetic forces, moving charged particles deviate from their original path in a direction perpendicular to the field (Fig. 34). The magnetic field is formed only around moving electric charges, and its action also extends only to moving charges. Magnetic and electric fields inseparable and form together a single electromagnetic field. Any change electric field leads to the appearance of a magnetic field and, conversely, any change in the magnetic field is accompanied by the appearance of an electric field. Electromagnetic field propagates at the speed of light, i.e. 300,000 km/s.

Graphic representation of the magnetic field. Graphically, the magnetic field is represented by magnetic lines of force, which are drawn so that the direction of the field line at each point of the field coincides with the direction of the field forces; magnetic field lines are always continuous and closed. The direction of the magnetic field at each point can be determined using a magnetic needle. The north pole of the arrow is always set in the direction of the field forces. The end of a permanent magnet, from which the field lines emerge (Fig. 35, a), is considered to be the north pole, and the opposite end, into which the field lines enter, is the south pole (the field lines passing inside the magnet are not shown). The distribution of field lines between the poles of a flat magnet can be detected using steel filings sprinkled on a sheet of paper placed on the poles (Fig. 35, b). The magnetic field in the air gap between two parallel opposite poles of a permanent magnet is characterized by a uniform distribution of magnetic force lines (Fig. 36) (field lines passing inside the magnet are not shown).

Rice. 37. Magnetic flux penetrating the coil when its positions are perpendicular (a) and inclined (b) relative to the direction of the magnetic lines of force.

For a more visual representation of the magnetic field, the field lines are placed less frequently or denser. In those places where the magnetic field is stronger, the lines of force are located closer friend to each other, in the same place where it is weaker, further away from each other. The lines of force do not intersect anywhere.

In many cases, it is convenient to consider magnetic lines of force as some elastic stretched threads that tend to contract and also repel each other (have mutual lateral thrust). This mechanical concept of lines of force makes it possible to clearly explain the emergence of electromagnetic forces during the interaction of a magnetic field and a conductor with current, as well as two magnetic fields.

The main characteristics of a magnetic field are magnetic induction, magnetic flux, magnetic permeability and magnetic field strength.

Magnetic induction and magnetic flux. The intensity of the magnetic field, i.e. its ability to produce work, is determined by a quantity called magnetic induction. The stronger the magnetic field created by a permanent magnet or electromagnet, the greater the induction it has. Magnetic induction B can be characterized by the density of magnetic field lines, i.e., the number of field lines passing through an area of 1 m 2 or 1 cm 2 located perpendicular to the magnetic field. There are homogeneous and inhomogeneous magnetic fields. In a uniform magnetic field, the magnetic induction at each point of the field has same value and direction. The field in the air gap between the opposite poles of a magnet or electromagnet (see Fig. 36) can be considered homogeneous at some distance from its edges. Magnetic flux Ф passing through any surface is determined total number magnetic lines of force penetrating this surface, for example coil 1 (Fig. 37, a), therefore, in a uniform magnetic field

F = BS (40)

where S is the cross-sectional area of the surface through which the magnetic field lines pass. It follows that in such a field the magnetic induction is equal to the flux divided by the cross-sectional area S:

B = F/S (41)

If any surface is located obliquely with respect to the direction of the magnetic field lines (Fig. 37, b), then the flux penetrating it will be less than if it is perpendicular to its position, i.e. Ф 2 will be less than Ф 1 .

In the SI system of units, magnetic flux is measured in webers (Wb), this unit has the dimension V*s (volt-second). Magnetic induction in SI units is measured in teslas (T); 1 T = 1 Wb/m2.

Magnetic permeability. Magnetic induction depends not only on the strength of the current passing through a straight conductor or coil, but also on the properties of the medium in which the magnetic field is created. The quantity characterizing the magnetic properties of a medium is absolute magnetic permeability? A. Its unit of measurement is henry per meter (1 H/m = 1 Ohm*s/m).
In a medium with greater magnetic permeability, an electric current of a certain strength creates a magnetic field with greater induction. It has been established that the magnetic permeability of air and all substances, with the exception of ferromagnetic materials (see § 18), has approximately the same value as the magnetic permeability of vacuum. The absolute magnetic permeability of a vacuum is called the magnetic constant, ? o = 4?*10 -7 H/m. The magnetic permeability of ferromagnetic materials is thousands and even tens of thousands of times greater than the magnetic permeability of non-ferromagnetic substances. Magnetic permeability ratio? and any substance to the magnetic permeability of vacuum? o is called relative magnetic permeability:

? = ? A /? O (42)

Magnetic field strength. The intensity And does not depend on the magnetic properties of the medium, but takes into account the influence of the current strength and the shape of the conductors on the intensity of the magnetic field at a given point in space. Magnetic induction and tension are related by the relation

H = B/? a = B/(?? o) (43)

Consequently, in a medium with constant magnetic permeability, the magnetic field induction is proportional to its strength.
Magnetic field strength is measured in amperes per meter (A/m) or amperes per centimeter (A/cm).

A MAGNETIC FIELD

A magnetic field is a special type of matter, invisible and intangible to humans,
existing independently of our consciousness.
Even in ancient times, scientific thinkers guessed that something existed around a magnet.

Magnetic needle.

A magnetic needle is a device necessary when studying the magnetic action of electric current.
It is a small magnet mounted on the tip of a needle and has two poles: north and south. The magnetic needle can rotate freely on the tip of the needle.
The northern end of the magnetic needle always points to "north".
The line connecting the poles of the magnetic needle is called the axis of the magnetic needle.
A similar magnetic needle is found in any compass - a device for orienting oneself.

Where does the magnetic field originate?

Oersted's experiment (1820) - shows how a conductor with current interacts with a magnetic needle.

When the electrical circuit is closed, the magnetic needle deviates from its original position; when the circuit is opened, the magnetic needle returns to its original position.

A magnetic field arises in the space around a conductor carrying current (and in the general case around any moving electric charge).
The magnetic forces of this field act on the needle and turn it.

In general, we can say
that a magnetic field arises around moving electric charges.
Electricity and magnetic field are inseparable from each other.

IT'S INTERESTING THAT...

Many celestial bodies– planets and stars have their own magnetic fields.
However, our closest neighbors - the Moon, Venus and Mars - do not have a magnetic field,
similar to earthly.
___

Gilbert discovered that when a piece of iron is brought closer to one pole of a magnet, the other pole begins to attract more strongly. This idea was patented only 250 years after Gilbert's death.

In the first half of the 90s, when new Georgian coins appeared - lari,
local pickpockets have acquired magnets,
because the metal from which these coins were made was well attracted by a magnet!

If you take a dollar bill by the corner and hold it near a powerful magnet
(for example, horseshoe-shaped), creating a non-uniform magnetic field, piece of paper
will deviate towards one of the poles. It turns out that the ink on the dollar bill contains iron salts.
possessing magnetic properties, so the dollar is attracted to one of the poles of the magnet.

If you hold a large magnet close to a carpenter's bubble level, the bubble will move.
The fact is that the bubble level is filled with diamagnetic fluid. When such a liquid is placed in a magnetic field, a magnetic field in the opposite direction is created inside it, and it is pushed out of the field. Therefore, the bubble in the liquid approaches the magnet.

YOU NEED TO KNOW ABOUT THEM!

The organizer of the magnetic compass business in the Russian Navy was a famous deviator scientist,
captain 1st rank, author scientific works according to the theory of the compass I.P. Belavanets.
Participant trip around the world on the frigate "Pallada" and participant Crimean War 1853-56 He was the first in the world to demagnetize a ship (1863)
and solved the problem of installing compasses inside an iron submarine.
In 1865 he was appointed head of the country's first Compass Observatory in Kronstadt.

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