Maximum magnetic flux. Magnetic field induction flux

magnetic induction - is the magnetic flux density at a given point in the field. The unit of magnetic induction is the tesla.(1 T \u003d 1 Wb / m 2).

Returning to the previously obtained expression (1), we can quantify magnetic flux through a certain surface as a product of the amount of charge flowing through a conductor aligned with the boundary of this surface with complete disappearance magnetic field, on the resistance of the electrical circuit through which these charges flow

.

In the experiments described above with a test coil (ring), it was removed to a distance at which all manifestations of the magnetic field disappeared. But you can simply move this coil within the field and at the same time electric charges will also move in it. Let us pass in expression (1) to increments

Ф + Δ Ф = r(q - Δ q) => Δ Ф = - rΔq => Δ q\u003d -Δ F / r

where Δ Ф and Δ q- increments of the flow and the number of charges. Miscellaneous signs increments are explained by the fact that the positive charge in the experiments with the removal of the coil corresponded to the disappearance of the field, i.e. negative increment of the magnetic flux.

With the help of a test turn, you can explore the entire space around a magnet or current coil and build lines, the direction of the tangents to which at each point will correspond to the direction of the magnetic induction vector B(Fig. 3)

These lines are called magnetic induction vector lines or magnetic lines .

The space of the magnetic field can be mentally divided by tubular surfaces formed by magnetic lines, and the surfaces can be chosen in such a way that the magnetic flux inside each such surface (tube) is numerically equal to one and depict graphically the axial lines of these tubes. Such tubes are called single, and the lines of their axes are called single magnetic lines . The picture of the magnetic field depicted with the help of single lines gives not only a qualitative, but also a quantitative idea of ​​it, because. in this case, the value of the magnetic induction vector turns out to be equal to the number of lines passing through a unit surface normal to the vector B, a the number of lines passing through any surface is equal to the value of the magnetic flux .

Magnetic lines are continuous and this principle can be mathematically represented as

those. magnetic flux passing through any closed surface zero .

Expression (4) is valid for the surface s any form. If we consider the magnetic flux passing through the surface formed by the turns of a cylindrical coil (Fig. 4), then it can be divided into surfaces formed by individual turns, i.e. s=s 1 +s 2 +...+s eight . Moreover, in the general case, different magnetic fluxes will pass through the surfaces of different turns. So in fig. 4, eight single coils pass through the surfaces of the central turns of the coil. magnetic lines, and only four through the surfaces of the extreme turns.

In order to determine the total magnetic flux passing through the surface of all turns, it is necessary to add the fluxes passing through the surfaces of individual turns, or, in other words, interlocking with individual turns. For example, the magnetic fluxes interlocking with the four upper turns of the coil in Fig. 4 will be equal to: F 1 =4; F 2 =4; F 3 =6; F 4 \u003d 8. Also, mirror-symmetrical with the bottom.

Flux linkage - the virtual (imaginary total) magnetic flux Ψ, interlocking with all turns of the coil, is numerically equal to the sum of the fluxes interlocking with individual turns: Ψ = w e F m, where F m- the magnetic flux created by the current passing through the coil, and w e is the equivalent or effective number of turns of the coil. The physical meaning of flux linkage is the coupling of magnetic fields of coil turns, which can be expressed by the coefficient (multiplicity) of flux linkage k= Ψ/Ф = w e.

That is, for the case shown in the figure, two mirror-symmetrical halves of the coil:

Ψ \u003d 2 (Ф 1 + Ф 2 + Ф 3 + Ф 4) \u003d 48

The virtuality, that is, the imaginary flux linkage, manifests itself in the fact that it does not represent a real magnetic flux, which no inductance can multiply, but the behavior of the coil impedance is such that it seems that the magnetic flux increases by a multiple of the effective number of turns, although in reality it is simply interaction of turns in the same field. If the coil increased the magnetic flux by its flux linkage, then it would be possible to create magnetic field multipliers on the coil even without current, because the flux linkage does not imply the closed circuit of the coil, but only the joint geometry of the proximity of the turns.

Often the actual distribution of the flux linkage over the turns of the coil is unknown, but it can be assumed to be uniform and the same for all turns if the real coil is replaced with an equivalent one with a different number of turns. w e, while maintaining the magnitude of the flux linkage Ψ = w e F m, where F m is the flux interlocking with the internal turns of the coil, and w e is the equivalent or effective number of turns of the coil. For the one considered in Fig. 4 cases w e \u003d Ψ / F 4 \u003d 48 / 8 \u003d 6.

MAGNETIC FLUX

MAGNETIC FLUX(symbol F), a measure of the strength and extent of the MAGNETIC FIELD. The flow through area A at right angles to the same magnetic field is Ф=mNA, where m is the magnetic PERMEABILITY of the medium, and H is the intensity of the magnetic field. The magnetic flux density is the flux per unit area (symbol B), which is equal to H. A change in the magnetic flux through an electrical conductor induces an ELECTROMOTION FORCE.

Scientific and technical encyclopedic dictionary.

See what "MAGNETIC FLOW" is in other dictionaries:

The flow of the magnetic induction vector B through any surface. magnetic flux through a small area dS, within which the vector B is unchanged, is equal to dФ = ВndS, where Bn is the projection of the vector onto the normal to the area dS. Magnetic flux Ф through the final ... ... Big encyclopedic Dictionary

- (flux of magnetic induction), flux Ф of the magnetic vector. induction B through c.l. surface. M. p. dФ through a small area dS, within which the vector B can be considered unchanged, is expressed by the product of the size of the area and the projection Bn of the vector onto ... ... Physical Encyclopedia

magnetic flux- Scalar value, equal to the flow magnetic induction. [GOST R 52002 2003] magnetic flux The flux of magnetic induction through a surface perpendicular to the magnetic field, defined as the product of magnetic induction at a given point and the area ... ... Technical Translator's Handbook

MAGNETIC FLUX- flux Ф of the magnetic induction vector (see (5)) В through the surface S, normal to the vector В in a uniform magnetic field. The unit of magnetic flux in SI (see) ... Great Polytechnic Encyclopedia

A value that characterizes the magnetic effect on a given surface. M. p. is measured by the number of magnetic lines of force passing through a given surface. Technical railway dictionary. M .: State transport ... ... Technical railway dictionary

magnetic flux - scalar, equal to the flux of magnetic induction... Source: ELEKTROTEHNIKA. TERMS AND DEFINITIONS OF BASIC CONCEPTS. GOST R 52002 2003 (approved by the Decree of the State Standard of the Russian Federation of 01/09/2003 N 3 st) ... Official terminology

The flow of the magnetic induction vector B through any surface. The magnetic flux through a small area dS, within which the vector B is unchanged, is equal to dФ = BndS, where Bn is the projection of the vector onto the normal to the area dS. Magnetic flux Ф through the final ... ... encyclopedic Dictionary

Classical electrodynamics ... Wikipedia

magnetic flux- , flux of magnetic induction flux of the vector of magnetic induction through any surface. For a closed surface, the total magnetic flux is zero, which reflects the solenoid nature of the magnetic field, i.e., the absence in nature of ... Encyclopedic Dictionary of Metallurgy

magnetic flux- 12. Magnetic flux Flux of magnetic induction Source: GOST 19880 74: Electrical engineering. Basic concepts. Terms and definitions original document 12 magnetic on ... Dictionary-reference book of terms of normative and technical documentation

Books

• , Mitkevich V.F. This book contains much that is not always given due attention when we are talking about the magnetic flux, and what has not yet been sufficiently clearly stated or has not been ...
• Magnetic flux and its transformation, VF Mitkevich This book will be produced in accordance with your order using Print-on-Demand technology. There is much in this book that is not always given due attention when it comes to…

Electric dipole moment
Electric charge
electrical induction
Electric field
electrostatic potential

magnetostatics
Biot-Savart-Laplace law Ampère's law Magnetic moment A magnetic field magnetic flux Magnetic induction

Electrodynamics
vector potential Dipole Potentials of Lienar - Wiechert Lorentz force Bias current Unipolar induction Maxwell's equations Electricity Electromotive force Electromagnetic induction Electromagnetic radiation Electromagnetic field

Electrical circuit
Ohm's law Kirchhoff's laws Inductance radio waveguide Resonator Electric capacity electrical conductivity Electrical resistance Electrical impedance

Notable scientists
Henry Cavendish Michael Faraday Nikola Tesla André-Marie Ampère Gustav Robert Kirchhoff James Clerk (Clark) Maxwell Henry Rudolf Hertz Albert Abraham Michelson Robert Andrews Milliken

See also: Portal:Physics

magnetic flux- physical quantity equal to the product of the modulus of the magnetic induction vector $\backslash vec\; B$ to the area S and the cosine of the angle α between vectors $\backslash vec\; B$ and normal $\backslash mathbf(n)$. Flow $\backslash Phi\_B$ as an integral of the magnetic induction vector $\backslash vec\; B$ through the end surface S is defined via the integral over the surface:

{{{1}}}

In this case, the vector element d S surface area S defined as

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Magnetic flux quantization

The values ​​of the magnetic flux Φ passing through

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An excerpt characterizing the Magnetic flux

- C "est bien, mais ne demenagez pas de chez le prince Basile. Il est bon d" avoir un ami comme le prince, she said, smiling at Prince Vasily. - J "en sais quelque chose. N" est ce pas? [That's good, but don't move away from Prince Vasily. It's good to have such a friend. I know something about it. Isn't it?] And you're still so young. You need advice. You are not angry with me that I use the rights of old women. - She fell silent, as women are always silent, waiting for something after they say about their years. - If you marry, then another matter. And she put them together in one look. Pierre did not look at Helen, and she at him. But she was still terribly close to him. He mumbled something and blushed.
Returning home, Pierre could not sleep for a long time, thinking about what had happened to him. What happened to him? Nothing. He only realized that the woman he knew as a child, about whom he absentmindedly said: “Yes, good,” when he was told that Helen was beautiful, he realized that this woman could belong to him.
“But she is stupid, I myself said she was stupid,” he thought. - There is something nasty in the feeling that she aroused in me, something forbidden. I was told that her brother Anatole was in love with her, and she was in love with him, that there was a whole story, and that Anatole was expelled from this. Her brother is Ippolit... Her father is Prince Vasily... This is not good, he thought; and at the same time as he was reasoning like this (these reasonings were still unfinished), he found himself smiling and realizing that another series of reasonings had surfaced because of the first ones, that at the same time he was thinking about her insignificance and dreaming about how she would be his wife, how she could love him, how she could be completely different, and how everything he thought and heard about her could be untrue. And he again saw her not as some kind of daughter of Prince Vasily, but saw her whole body, only covered with a gray dress. “But no, why didn’t this thought occur to me before?” And again he told himself that it was impossible; that something nasty, unnatural, as it seemed to him, dishonest would be in this marriage. He remembered her former words, looks, and the words and looks of those who had seen them together. He remembered the words and glances of Anna Pavlovna when she told him about the house, remembered thousands of such hints from Prince Vasily and others, and he was horrified that he had not bound himself in any way in the performance of such a thing, which, obviously, was not good. and which he must not do. But at the same time as he was expressing this decision to himself, from the other side of his soul her image surfaced with all its feminine beauty.

In November 1805, Prince Vasily had to go to four provinces for an audit. He arranged this appointment for himself in order to visit his ruined estates at the same time, and taking with him (at the location of his regiment) his son Anatole, together with him to call on Prince Nikolai Andreevich Bolkonsky in order to marry his son to the daughter of this rich old man. But before leaving and these new affairs, Prince Vasily had to settle matters with Pierre, who, it is true, had spent whole days at home, that is, with Prince Vasily, with whom he lived, he was ridiculous, agitated and stupid (as he should being in love) in Helen's presence, but still not proposing.

Magnetic materials are those that are subject to the influence of special force fields, in turn, non-magnetic materials are not subject to or weakly subject to the forces of a magnetic field, which is usually represented by lines of force (magnetic flux) that have certain properties. In addition to always forming closed loops, they behave as if they are elastic, that is, during the distortion, they try to return to their previous distance and to their natural shape.

invisible force

Magnets tend to attract certain metals, especially iron and steel, as well as nickel, nickel, chromium and cobalt alloys. Materials that create attractive forces are magnets. There are various types. Materials that can be easily magnetized are called ferromagnetic. They can be hard or soft. Soft ferromagnetic materials such as iron lose their properties quickly. Magnets made from these materials are called temporary. Rigid materials such as steel hold their properties much longer and are used as permanent materials.

Magnetic Flux: Definition and Characterization

Around the magnet there is a certain force field, and this creates the possibility of energy. The magnetic flux is equal to the product of the average force fields of the perpendicular surface into which it penetrates. It is depicted using the symbol "Φ", it is measured in units called Webers (WB). The amount of flow passing through a given area will vary from one point to another around the object. Thus, magnetic flux is a so-called measure of the strength of a magnetic field or electric current, based on the total number of charged lines of force passing through a certain area.

Revealing the mystery of magnetic fluxes

All magnets, regardless of their shape, have two areas, called poles, capable of producing a certain chain of organized and balanced system of invisible lines of force. These lines from the stream form a special field, the form of which is more intense in some parts than in others. The areas with the greatest attraction are called poles. Vector field lines cannot be detected with the naked eye. Visually, they always appear as lines of force with unambiguous poles at each end of the material, where the lines are denser and more concentrated. Magnetic flux is lines that create vibrations of attraction or repulsion, showing their direction and intensity.

Magnetic flux lines

Magnetic lines of force are defined as curves that move along a certain path in a magnetic field. The tangent to these curves at any point shows the direction of the magnetic field in it. Characteristics:

Each flow line forms a closed loop.

These induction lines never intersect, but tend to shrink or stretch, changing their dimensions in one direction or another.

As a rule, lines of force have a beginning and an end on the surface.

There is also a certain direction from north to south.

Field lines that are close to each other, forming a strong magnetic field.

• When adjacent poles are the same (north-north or south-south), they repel each other. When neighboring poles are not aligned (north-south or south-north), they are attracted to each other. This effect is reminiscent of the famous expression that opposites attract.

Magnetic molecules and Weber's theory

Weber's theory is based on the fact that all atoms have magnetic properties due to the bond between electrons in atoms. Groups of atoms join together in such a way that the fields surrounding them rotate in the same direction. This kind of material is made up of groups of tiny magnets (if you look at them on molecular level) around the atoms, this means that the ferromagnetic material is composed of molecules that have attractive forces. They are known as dipoles and are grouped into domains. When the material is magnetized, all the domains become one. A material loses its ability to attract and repel when its domains are separated. Dipoles together form a magnet, but individually, each of them tries to repel the unipolar one, thus attracting opposite poles.

Fields and poles

The strength and direction of the magnetic field is determined by the magnetic flux lines. The area of ​​attraction is stronger where the lines are close to each other. The lines are closest to the pole of the rod base, where the attraction is strongest. The planet Earth itself is in this powerful force field. It acts as if a giant striped magnetized plate is running through the middle of the planet. The north pole of the compass needle is directed towards a point called the North magnetic pole, the south pole it points to the magnetic south. However, these directions differ from the geographic North and South Poles.

The nature of magnetism

Magnetism plays an important role in electrical and electronic engineering, because without its components such as relays, solenoids, inductors, chokes, coils, loudspeakers, electric motors, generators, transformers, electricity meters, etc. will not work. Magnets can be found in natural state in the form of magnetic ores. There are two main types, these are magnetite (also called iron oxide) and magnetic ironstone. The molecular structure of this material in the non-magnetic state is presented as a free magnetic circuit or individual tiny particles that are freely arranged in a random order. When a material is magnetized, this random arrangement of molecules changes, and tiny random molecular particles line up in such a way that they produce a whole series of arrangements. This idea of ​​molecular alignment of ferromagnetic materials is called Weber's theory.

Measurement and practical application

The most common generators use magnetic flux to generate electricity. Its strength is widely used in electrical generators. The device that measures this interesting phenomenon is called a fluxmeter, it consists of a coil and electronic equipment that evaluates the change in voltage in the coil. In physics, a flow is an indicator of the number of lines of force passing through a certain area. Magnetic flux is a measure of the number of magnetic lines of force.

Sometimes even a non-magnetic material can also have diamagnetic and paramagnetic properties. An interesting fact is that the forces of attraction can be destroyed by heating or being struck with a hammer of the same material, but they cannot be destroyed or isolated by simply breaking a large specimen in two. Each broken piece will have its own north and south pole, no matter how small the pieces are.

If a electricity, as Oersted's experiments showed, creates a magnetic field, then can the magnetic field in turn cause an electric current in the conductor? Many scientists with the help of experiments tried to find the answer to this question, but Michael Faraday (1791 - 1867) was the first to solve this problem.
In 1831, Faraday discovered that an electric current arises in a closed conducting circuit when the magnetic field changes. This current is called induction current.
Induction current in a coil of metal wire occurs when the magnet is pushed into the coil and when the magnet is pulled out of the coil (Fig. 192),

and also when the current strength changes in the second coil, the magnetic field of which penetrates the first coil (Fig. 193).

The phenomenon of the occurrence of an electric current in a closed conducting circuit with changes in the magnetic field penetrating the circuit is called electromagnetic induction.
The appearance of an electric current in a closed circuit with changes in the magnetic field penetrating the circuit indicates the action of external forces of a non-electrostatic nature in the circuit or the occurrence EMF of induction. Quantitative description of the phenomenon electromagnetic induction is given on the basis of establishing a connection between the induction emf and physical quantity called magnetic flux.
magnetic flux. For a flat circuit located in a uniform magnetic field (Fig. 194), the magnetic flux F through a surface area S call the value equal to the product of the modulus of the magnetic induction vector and the area S and by the cosine of the angle between the vector and the normal to the surface:

Lenz's rule. Experience shows that the direction of the inductive current in the circuit depends on whether the magnetic flux penetrating the circuit increases or decreases, as well as on the direction of the magnetic field induction vector relative to the circuit. General rule, allowing to determine the direction of the induction current in the circuit, was established in 1833 by E. X. Lenz.
Lenz's rule can be visualized with with the help of a lung aluminum ring (Fig. 195).

Experience shows that when making permanent magnet the ring is repelled from it, and when removed it is attracted to the magnet. The result of the experiments does not depend on the polarity of the magnet.
The repulsion and attraction of a solid ring is explained by the occurrence of an induction current in the ring with changes in the magnetic flux through the ring and the action on induction current magnetic field. Obviously, when the magnet is pushed into the ring, the induction current in it has such a direction that the magnetic field created by this current counteracts the external magnetic field, and when the magnet is pushed out, the induction current in it has such a direction that the induction vector of its magnetic field coincides in direction with the vector external field induction.
General wording Lenz's rules: the induction current arising in a closed circuit has such a direction that the magnetic flux created by it through the area bounded by the circuit tends to compensate for the change in the magnetic flux that causes this current.
The law of electromagnetic induction. Pilot study dependence of the induction emf on the change in the magnetic flux led to the establishment law of electromagnetic induction: The induction emf in a closed loop is proportional to the rate of change of the magnetic flux through the surface bounded by the loop.
In SI, the unit of magnetic flux is chosen such that the coefficient of proportionality between the induction emf and the change in magnetic flux is equal to one. Wherein law of electromagnetic induction is formulated as follows: EMF of induction in a closed loop is equal to the modulus of the rate of change of the magnetic flux through the surface bounded by the loop:

Taking into account the Lenz rule, the law of electromagnetic induction is written as follows:

EMF of induction in the coil. If identical changes in the magnetic flux occur in series-connected circuits, then the induction EMF in them is equal to the sum of the induction EMF in each of the circuits. Therefore, when changing the magnetic flux in the coil, consisting of n identical turns of wire, the total induction emf in n times more EMF induction in a single circuit:

For a uniform magnetic field, on the basis of equation (54.1), it follows that its magnetic induction is 1 T if the magnetic flux through a 1 m 2 circuit is 1 Wb:

.

Vortex electric field. The law of electromagnetic induction (54.3) according to known speed changes in the magnetic flux allows you to find the value of the induction EMF in the circuit and at known value electrical resistance loop calculate the current in the loop. However, it remains undisclosed physical meaning phenomena of electromagnetic induction. Let's consider this phenomenon in more detail.

The occurrence of an electric current in a closed circuit indicates that when the magnetic flux penetrating the circuit changes, forces act on free electric charges in the circuit. The wire of the circuit is motionless, free electric charges in it can be considered motionless. Only an electric field can act on stationary electric charges. Therefore, with any change in the magnetic field in the surrounding space, an electric field arises. This electric field sets in motion free electric charges in the circuit, creating an induction electric current. The electric field that occurs when the magnetic field changes is called vortex electric field.

The work of the forces of the vortex electric field on the movement of electric charges and is the work of external forces, the source of the induction EMF.

A vortex electric field differs from an electrostatic field in that it is not related to electric charges, its lines of tension are closed lines. The work of the forces of the vortex electric field during the movement of an electric charge along closed line may be different from zero.

EMF of induction in moving conductors. The phenomenon of electromagnetic induction is also observed in cases where the magnetic field does not change in time, but the magnetic flux through the circuit changes due to the movement of the circuit conductors in the magnetic field. In this case, the cause of the induction EMF is not the vortex electric field, but the Lorentz force.