EDS self-induction definition. What is the EMF of self-induction
The invention relates to electrical engineering, in particular to the designs of induction current generators, and can be used in electromagnetic installations and electrical machines, such as motors, generators, transformers, in particular, as a step-up transformer. The technical result consists in increasing the emf at the output by using pulsed voltages on the secondary winding and implementing a secondary winding design that would allow direct removal of the resulting pulsed voltage from the generator, and at the same time the total power of the primary and secondary windings. 6 w.p. f-ly, 2 ill.
Drawings to the RF patent 2524387
The invention relates to electrical engineering, in particular to designs of pulsed induction current generators.
The purpose of this invention is the use of a pulse generator EMF self-induction to provide pulsed power supply for various electromagnetic installations and electrical machines, which allows you to significantly expand the arsenal of pulsed energy sources. The prior art known "Induction synchronous generator", Application RU 9811934 7, publ. 09/10/2000, IPC H02K 21/14, using the currents of the stator winding, on the armature of which the currents pulsate, and the inductor (rotor), made protected from magnetic field stator armature winding currents. Allows you to expand the operating modes of the generator. However, the generator contains rotating parts, and therefore, it has all the disadvantages of such generators, i.e. the problems connected with switching of the electric power are not solved. In the proposed design, it is impossible to obtain the required high voltage.
Known for Generator electrical energy", application RU 9402533 5, publ. 06/10/1996, IPC H02K 19/16, containing composite ring windings with a core, an induction coil and an excitation winding. Allows you to increase the performance of the electric power generator, reduce the inductive resistance of the stator winding, reduce the cost of mechanical work when converting mechanical energy into electrical energy and increase efficiency. However, the generator, due to the design features, does not allow the use of self-induction EMF. The generator contains rotating parts, and, therefore, it has all the disadvantages of such generators, i.e. the problems connected with switching of the electric power are not solved.
Known utility model"Combined electromagnetic winding", patent RU 96443, publ. 07/27/2010, IPC H01F 5/00, in which there are two or more conductors with leads, and the conductors are separated by a dielectric. Allows you to expand the modes of operation. However, both conductors are used as the primary winding, there is no high voltage secondary winding, which does not allow the winding to be used in high voltage transformers, and also does not ensure the removal and use of induction EMF from the secondary winding.
The closest application for the invention is "Inductive-static method for generating electrical energy and a device for its implementation", RU 2004124018, publ. 01/27/2006, IPC H01F 1/00, according to which there are primary and secondary windings that form an inductor with the transition of free magnetic energy to an inductively-dependent state, and the EMF of induction is induced and magnetic flux density is obtained, proportional to the increase electrical power. Allows the use of a secondary winding with an inductance that is less by the amount of magnetic flux compaction, which achieves proportional compaction and an increase in the electric power of the generator. The method uses induction and, at the same time, static methods of generation. However, the design of the secondary winding of the generator has not been proposed, which allows direct removal from the generator of the resulting pulsed voltage and self-induction EMF current.
Also, the closest solution is the classical circuit diagram for demonstration experiments electromagnetic induction when the circuit is opened. This circuit (device) is functionally a self-induction EMF pulse generator. In connection with the foregoing, as a prototype, we accept the installation shown in the drawing - fig. 424 p. 231, textbook: Physics course, part two, ed. "Nauka", Moscow 1970 Authors: L.S. Zhdanov, V.A. Maranjan.
However, in the classical scheme, the core of electrical steel is structurally unable to perform two functions in the device simultaneously: an electrically conductive winding and a classic, as in Fig. 424 prototype, magnetic circuit, i.e. the core (M) of an induction coil. The prototype does not allow direct removal and use of the self-induction EMF that occurs in the core of a classical induction coil.
The objective of the proposed invention is the use of impulse voltages and the implementation of the design of the secondary winding of the generator, which would allow direct removal from the generator of the resulting impulse voltage.
The technical result that the proposed technical solution provides is a significant expansion of the arsenal of means for pulsed generation and conversion of electricity. Claimed technical result provided due to the fact that the self-induction EMF pulse generator is structurally designed in the form of primary and secondary windings of a single-phase step-up transformer in a standard technical performance(taking into account the fact that the secondary winding is both functionally an electrical conductor and a magnetic circuit, it is proposed to consider the presented design as the simplest induction coil with a core designed in the form of a spiral coil with the possibility of removing self-induction EMF from it) and they are equipped with two or more conductors, which separated by a dielectric and each conductor has terminals. The generator differs in that the primary winding (conductor) of low voltage is made of spiral tape and has at least 2 turns wound tightly or with a small gap, turn to turn, the winding tape is made with a width of 120 to 200 mm and a thickness of 1 to 2 mm; the secondary winding (conductor) of high voltage is also made of spiral tape, the winding tape is made of electrical steel coated with electrical insulation and has at least 100 turns wound tightly or with a small gap, turn to turn, the tape is made with a width of 120 to 200 mm and not more than 0.1 mm thick. The primary winding is electrically connected to the low voltage storage battery through a switch to form a closed electrical circuit, where the secondary winding is both an electrically conductive winding and a magnetic circuit. In this case, the turns of the primary winding are located outside the turns of the secondary winding in such a way that both windings form a step-up transformer, in which the secondary winding is an induction coil of a high voltage transformer, providing electrical conductivity due to the electrical steel tape insulated with an outer layer of insulation and, at the same time, performs the function core for the primary winding, the EMF is removed by means of conductors electrically connected to the ends of the secondary winding tape, and is obtained due to the periodic operation of the breaker key, and due to the frequency of operation of the breaker key, the calculated impulse voltage and current arising in the secondary winding are provided by the formula
where - where L is the inductance of the circuit or the coefficient of proportionality between the rate of change of the current strength in the circuit and the resulting EMF of self-induction,
- the rate of change of current strength in the electrical circuit
In particular cases, the primary winding can be made of a copper or aluminum conductor, it can have 3 turns or more, the number of turns is limited by the transformer ratio: the ratio of the number of turns of the secondary winding to the number of turns of the primary winding, which determines the transformation ratio, i.e. how much voltage in the secondary winding is greater than in the primary. For example, accumulator battery low voltage can be rated at 12-24 volts and it is a source direct current. In particular, periodic operation of the breaker key is carried out with an industrial frequency of alternating current of 50 Hz. In this case, the frequencies can be any technically possible for implementation, but 50 Hz is better, since it is easier to convert or consume it using the available standard converters or electrical appliances. The calculated EMF of self-induction in the secondary winding is provided, in particular, by the geometry of the circuit and the magnetic properties of the core for the primary winding. So it can be made with a contour shape, which is made round with a diameter of 150 mm or more, which depends on the transformation ratio, which determines the diameter of the secondary winding, depending on the thickness of the electrical steel used, or a round spiral shape. Since the secondary winding is a high voltage winding and is made of electrical steel, this means that its magnetic properties are determined by the material itself (i.e., the actual magnetic properties of electrical steel).
The invention in the most generalized form is illustrated in the drawings. Specific design is not limited to the embodiments shown in the drawings.
Figure 1 shows the layout of the primary and secondary windings and a battery with a key breaker.
Figure 2 shows section A-A along the connected secondary and primary windings.
This technical solution is illustrated by a drawing, which does not cover all possible design options for the presented connection diagram.
The device of the EMF pulse generator of self-induction is shown in figure 1 and figure 2 (in section), and this device is structurally made in the form of a single-phase step-up transformer (and also structurally is the simplest induction coil), which consists of a primary (1) spiral tape winding (copper or aluminum conductor), 2-3 turns 1-2 mm thick, 120 mm wide, connected to a low voltage battery (2) 12-24 V - a direct current source through a breaker key (3), forming a closed electrical circuit .
Secondary high voltage spiral-tape winding (4) made of electrical steel coated with electrical insulation, has a number of turns of 100 or more, tape thickness 0.1 mm, width 120 mm.
The secondary winding (4) made of electrical steel performs two functions in the structure at the same time: an electrically conductive winding and a magnetic circuit.
As an electrical conductor, the secondary winding (4) is the high voltage induction coil of a step-up transformer.
As a magnetic circuit, the secondary winding (4) is the core for the primary winding (2) of a classical induction coil.
The primary (1) and secondary (4) windings of a single-phase step-up transformer and are equipped with two or more conductors (5), the secondary winding conductors have a terminal (6) - i.e. EMF is removed by means of conductors (5, 6) electrically connected to the ends of the secondary winding tape, and is obtained due to the periodic operation of the breaker key (3). Moreover, the currents arising in the secondary winding are calculated by the formula 
where L is the inductance of the circuit or the coefficient of proportionality between the rate of change of the current strength in the circuit of the primary winding (1) and the resulting EMF of self-induction in the secondary winding (2),
- the rate of change in the current strength in the electrical circuit of the primary winding (1) due to the breaker key (3).
Periodic operation of the key-breaker (3) is carried out with an industrial frequency of alternating current of 50 Hz. The calculated EMF of self-induction in the secondary winding (4) is provided by the geometry of the circuit of the secondary winding (4) and the magnetic properties of the core (4) for the primary winding (1).
The shape of the circuit obtained by the primary (1) and secondary (4) windings, in the presented version, is made with a round diameter of 150 mm or more.
The device works as follows.
When the key (3) closes the electrical circuit of the primary winding (1), a magnetic field arises, the energy of which is stored in the magnetic field of the secondary winding (4).
Opening the key (3) of the circuit of the primary winding (1) forms a decreasing current, which, according to the Lenz rule, tends to maintain the EMF of the induced induction of the secondary winding (4).
As a result, the energy stored in the magnetic field of the secondary winding (4) is converted into additional energy of the self-induction current of the primary winding (1), which feeds the electrical circuit of the secondary winding (4).
Depending on the amount of magnetic energy stored in the secondary winding (4) circuit, the power of the self-induction current can be different and is determined by the well-known formula:
Thus, this invention achieves the technical result, which consists in the fact that the design, material and dual functionality of the secondary winding of the device allows you to remove and effectively use the resulting self-induction EMF.
Industrial applicability of the proposed technical solution confirmed general rules physics. So, the effect of self-induction is described in the textbook (L.S. Zhdanov, V.A. Marandzhyan, physics course for average special institutions, part 2 electricity, ed. Third, stereotypical, main edition of physical and mathematical literature, M., 1970, pp. 231,232,233). Self-induction occurs when the circuit opens, it is directly proportional to the rate of change in the current strength in the electrical circuit. In traditional circuits, the phenomenon of self-induction is always accompanied by the appearance of a spark that occurs at the point of breaking the circuit. Since in the proposed design there is no break in the electrical circuit in the secondary winding (4) due to its design, depending on the amount of magnetic energy stored in this circuit, the breaking current does not spark, but passes into the generated power. Thus, in the design of the secondary winding (4), when the DC circuit in the primary winding (1) is opened, the energy stored in the magnetic field of this circuit is converted into the energy of the self-induction current in the secondary winding circuit (4).
Since the electromotive force (EMF) is the quantity equal to work external forces, in our case, this is the changing magnetic field of the primary coil (1), referred to a unit of positive charge, this is the EMF acting in the circuit or in its section, in our case, this is the secondary winding (4). External forces can be characterized by the work they do on charges moving along the chain, and the dimension of the EMF coincides with the dimension of the potential and is measured in the same units. Therefore, the vector quantity E is also called the field strength of external forces. The field of external forces in our case arises due to the alternating magnetic field in the primary winding (1). Thus, the EMF acting in a closed circuit can be defined as the circulation of the field strength vector of external forces, i.e. external forces arising in the primary winding (1) due to interruption electric field key-breaker (3). This rule ensures the occurrence of induction EMF in the secondary winding (4). This physical phenomenon is described in the textbook (I.V. Savelyev, Course of Physics, volume 2, electricity, pp. 84,85, ed. Second stereotypical, ed. Science, main edition of physical and mathematical literature, M., 1966. ).
In addition to external forces, the charge is affected by the forces of the electrostatic field, which arise directly in the secondary coil (4).
The device also uses the phenomenon of electromagnetic induction described in (R.A. Mustafaev, V.G. Krivtsov, textbook, physics, to help university applicants, ed. M., graduate School, 1989).
Thus, the design of the generator used in the proposed invention as a device makes it possible to efficiently generate, remove and use self-induction EMF. Thus, the device can be made industrial way and be introduced as a promising efficient self-induction EMF pulse generator, which allows expanding the arsenal technical means for impulse generation and conversion of electricity.
CLAIM
1. A pulsed self-induction emf generator, designed in the form of a single-phase step-up transformer, consisting of primary and secondary windings and equipped with two or more conductors that are separated by a dielectric, and the conductor has leads, characterized in that the low-voltage primary winding is made of spiral tape and has at least two turns wound tightly or at a small distance from each other, the winding tape is made 120-200 mm wide and 1-2 mm thick; the secondary high voltage winding is also made of spiral tape, the winding tape is made of electrical steel coated with electrical insulation, has at least 100 turns wound tightly or at a small distance from each other, the tape is made 120-200 mm wide and not more than 0 thick, 1 mm, the primary winding is electrically connected to the low-voltage battery through a key-breaker to form a closed electrical circuit, and the secondary winding is both an electrically conductive winding and a magnetic circuit, while the turns of the primary winding are located outside the turns of the secondary winding in such a way that both windings form a step-up transformer, in which the secondary winding is an induction coil of a step-up transformer, providing electrical conductivity due to an electrical steel tape insulated with an outer layer of insulation, and at the same time acts as a core for the primary winding, the emf is removed by means of conductors , electrically connected to the ends of the secondary winding tape, and are obtained due to the periodic operation of the breaker key.
2. Pulse generator emf self-induction according to claim 1, characterized in that the primary winding is made of copper or aluminum conductor.
3. Pulse generator emf self-induction according to claim 1, characterized in that the primary winding has three turns.
4. Pulse generator emf self-induction according to claim 1, characterized in that the low voltage battery is designed for 12-24 volts and is a source of direct current.
5. Pulse generator emf self-induction according to claim 1, characterized in that the periodic operation of the key-breaker is carried out with an industrial frequency of alternating current 50 Hz.
6. The self-induction pulse generator according to claim 1, characterized in that the calculated self-induction emf is provided by the geometry of the circuit and the magnetic properties of the core for the primary winding.
7. Pulse generator emf self-induction according to claim 1, characterized in that the shape of the circuit is made round with a diameter of 150 mm or more.
Electromagnetic induction - the generation of electric currents by magnetic fields that change over time. The discovery of this phenomenon by Faraday and Henry introduced a certain symmetry to the world of electromagnetism. Maxwell in one theory managed to collect knowledge about electricity and magnetism. His research predicted the existence electromagnetic waves before experimental observations. Hertz proved their existence and opened the era of telecommunications to mankind.
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Faraday's experiments
Faraday and Lenz laws
Electric currents create magnetic effects. Is it possible for a magnetic field to generate an electric one? Faraday discovered that the desired effects arise due to changes in the magnetic field over time.
When a conductor is crossed by an alternating magnetic flux, an electromotive force is induced in it, causing an electric current. The system that generates current can be permanent magnet or electromagnet.
The phenomenon of electromagnetic induction is governed by two laws: Faraday's and Lenz's.
Lenz's law allows you to characterize the electromotive force with respect to its direction.
Important! The direction of the induced emf is such that the current it causes tends to oppose the cause that creates it.
Faraday noticed that the intensity of the induced current increases when the number of field lines traversing the circuit changes faster. In other words, the EMF of electromagnetic induction is directly dependent on the speed of the moving magnetic flux.
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EMF induction
The induction emf formula is defined as:
E \u003d - dF / dt.
The "-" sign shows how the polarity of the induced emf is related to the sign of the flux and the changing speed.
A general formulation of the law of electromagnetic induction is obtained, from which expressions for particular cases can be derived.
The movement of a wire in a magnetic field
When a wire of length l moves in a magnetic field with induction B, an EMF will be induced inside it, proportional to its linear velocity v. To calculate the EMF, the formula is used:
- in the case of conductor movement perpendicular to the direction of the magnetic field:
E \u003d - B x l x v;
- in case of movement at a different angle α:
E \u003d - B x l x v x sin α.
The induced emf and current will be directed in the direction we find using the rule right hand: By placing your hand perpendicular to the magnetic field lines and pointing your thumb in the direction of the conductor movement, you can find out the direction of the EMF by the remaining four straightened fingers.
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Moving a wire in MP
Rotating coil
The operation of the electric power generator is based on the rotation of the circuit in the MP, which has N turns.
EMF is induced in the electrical circuit whenever the magnetic flux crosses it, in accordance with the definition of the magnetic flux Ф = B x S x cos α (magnetic induction multiplied by the surface area through which the MP passes, and the cosine of the angle formed by the vector B and the perpendicular line to the plane S).
It follows from the formula that F is subject to changes in the following cases:
- the intensity of the MF changes - the vector B;
- the area bounded by the contour varies;
- the orientation between them, given by the angle, changes.
In the first experiments of Faraday, induced currents were obtained by changing the magnetic field B. However, it is possible to induce an EMF without moving the magnet or changing the current, but simply by rotating the coil around its axis in the magnetic field. In this case, the magnetic flux changes due to a change in the angle α. The coil, during rotation, crosses the lines of the MP, an emf arises.
If the coil rotates uniformly, this periodic change results in a periodic change in magnetic flux. Or the number of MF lines of force crossed every second takes equal values with equal time intervals.
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Contour rotation in MP
Important! The induced emf changes with the orientation over time from positive to negative and vice versa. The graphical representation of the EMF is a sinusoidal line.
For the formula for the EMF of electromagnetic induction, the expression is used:
E \u003d B x ω x S x N x sin ωt, where:
- S is the area limited by one turn or frame;
- N is the number of turns;
- ω is the angular velocity with which the coil rotates;
- B – MF induction;
- angle α = ωt.
In practice, in alternators, often the coil remains stationary (stator) and the electromagnet rotates around it (rotor).
EMF self-induction
When passing through the coil alternating current, it generates a variable magnetic field, which has a changing magnetic flux that induces an EMF. This effect is called self-induction.
Since the MP is proportional to the intensity of the current, then:
where L is the inductance (H), determined by geometric quantities: the number of turns per unit length and the dimensions of their cross section.
For the induction emf, the formula takes the form:
E \u003d - L x dI / dt.
Mutual induction
If two coils are located side by side, then an EMF of mutual induction is induced in them, depending on the geometry of both circuits and their orientation relative to each other. When the separation of the circuits increases, the mutual inductance decreases, as the magnetic flux connecting them decreases.
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Mutual induction
Let there be two coils. Through the wire of one coil with N1 turns, current I1 flows, creating an MF passing through the coil with N2 turns. Then:
- Mutual inductance of the second coil relative to the first:
M21 = (N2 x F21)/I1;
- Magnetic Flux:
F21 = (M21/N2) x I1;
- Find the induced emf:
E2 = - N2 x dФ21/dt = - M21x dI1/dt;
- EMF is induced identically in the first coil:
E1 = - M12 x dI2/dt;
Important! The electromotive force caused by mutual inductance in one coil is always proportional to the change in electric current in the other.
Mutual inductance can be considered equal to:
M12 = M21 = M.
Accordingly, E1 = - M x dI2/dt and E2 = M x dI1/dt.
M = K √ (L1 x L2),
where K is the coupling coefficient between two inductances.
The phenomenon of mutual inductance is used in transformers - electrical devices that allow you to change the value of the voltage of an alternating electric current. The device consists of two coils wound around one core. The current present in the first one creates a changing magnetic field in the magnetic circuit and an electric current in the other coil. If the number of turns of the first winding is less than the other, the voltage increases and vice versa.
This phenomenon is called self-induction. (The concept is related to the concept of mutual induction, being, as it were, a special case of it).
The direction of the EMF of self-induction always turns out to be such that when the current in the circuit increases, the EMF of self-induction prevents this increase (directed against the current), and when the current decreases, it decreases (co-directed with the current). With this property, the EMF of self-induction is similar to the force of inertia.
The value of the EMF of self-induction is proportional to the rate of change of the current:
.The proportionality factor is called self-induction coefficient or inductance circuit (coil).
Self-induction and sinusoidal current
In the case of a sinusoidal dependence of the current flowing through the coil on time, the self-induction EMF in the coil lags the current in phase by (that is, 90 °), and the amplitude of this EMF is proportional to the current amplitude, frequency and inductance (). After all, the rate of change of a function is its first derivative, and .
To calculate more or less complex circuits containing inductive elements, i.e. turns, coils, etc. devices in which self-induction is observed, (especially, completely linear, that is, not containing non-linear elements) in the case of sinusoidal currents and voltages, the method of complex impedances is used or, in more simple cases, a less powerful, but more visual version of it is the method of vector diagrams.
Note that everything described is applicable not only directly to sinusoidal currents and voltages, but also practically to arbitrary ones, since the latter can almost always be expanded into a series or Fourier integral and thus reduced to sinusoidal ones.
In more or less direct connection with this, one can mention the application of the phenomenon of self-induction (and, accordingly, inductors) in various oscillatory circuits, filters, delay lines and other various circuits of electronics and electrical engineering.
Self-induction and current surge
Due to the phenomenon of self-induction in an electric circuit with an EMF source, when the circuit is closed, the current is not established instantly, but after some time. Similar processes also occur when the circuit is opened, while (with a sharp opening) the value of the self-induction emf can at this moment significantly exceed the source emf.
Most often in ordinary life it is used in the ignition coils of automobiles. Typical ignition voltage at 12V battery voltage is 7-25 kV. However, the excess of the EMF in the output circuit over the EMF of the battery here is due not only to a sharp interruption of the current, but also to the transformation ratio, since most often it is not a simple inductor coil that is used, but a transformer coil, the secondary winding of which, as a rule, has many times large quantity turns (that is, in most cases, the circuit is somewhat more complex than the one whose operation would be fully explained through self-induction; however, the physics of its operation in this version partly coincides with the physics of the operation of a circuit with a simple coil).
This phenomenon is also applied to ignition fluorescent lamps in standard traditional pattern(here we are talking specifically about a circuit with a simple inductor - a choke).
In addition, it must always be taken into account when opening contacts, if the current flows through the load with a noticeable inductance: the resulting jump in the EMF can lead to a breakdown of the intercontact gap and / or other undesirable effects, to suppress which in this case, as a rule, it is necessary to take a variety of special measures.
Notes
Links
- About self-induction and mutual induction from the "School for an Electrician"
Wikimedia Foundation. 2010 .
- Bourdon, Robert Gregory
- Juan Amar
See what "Self-induction" is in other dictionaries:
self-induction- self-induction ... Spelling Dictionary
SELF-INDUCTION- the occurrence of induction emf in a conducting circuit when the current strength changes in it; special cases of electromagnetic induction. When the current in the circuit changes, the magnetic flux changes. induction through the surface bounded by this contour, resulting in ... Physical Encyclopedia
SELF-INDUCTION- excitation of the electromotive force of induction (emf) in an electric circuit when the electric current in this circuit changes; special case electromagnetic induction. The electromotive force of self-induction is directly proportional to the rate of change of current; ... ... Big Encyclopedic Dictionary
SELF-INDUCTION- SELF-INDUCTION, self-induction, for women. (physical). 1. only units The phenomenon that when a current changes in a conductor, an electromotive force appears in it, preventing this change. Self-induction coil. 2. A device that has ... ... Dictionary Ushakov
SELF-INDUCTION- (Self induction) 1. A device with inductive resistance. 2. The phenomenon consisting in the fact that when an electric current changes in magnitude and direction in a conductor, an electromotive force arises in it that prevents this ... ... Marine Dictionary
SELF-INDUCTION- guidance of the electromotive force in the wires, as well as in the windings of electr. machines, transformers, apparatus and instruments when changing the magnitude or direction of the electric current flowing through them. current. The current flowing through the wires and windings creates around them ... ... Technical railway dictionary
self induction- electromagnetic induction caused by a change in the magnetic flux interlocking with the circuit, due to the electric current in this circuit ... Source: ELEKTROTEHNIKA. TERMS AND DEFINITIONS OF BASIC CONCEPTS. GOST R 52002 2003 (approved ... ... Official terminology
self-induction- noun, number of synonyms: 1 electromotive force excitation (1) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary
self-induction- Electromagnetic induction, caused by a change in the magnetic flux interlocking with the circuit, due to the electric current in this circuit. [GOST R 52002 2003] EN self induction electromagnetic induction in a tube of current due to variations… … Technical Translator's Handbook
SELF-INDUCTION- a special case of electromagnetic induction (see (2)), consisting in the occurrence of an induced (induced) EMF in a circuit and due to changes in time of the magnetic field created by a varying current flowing in the same circuit. ... ... Great Polytechnic Encyclopedia
Books
- A set of tables. Physics. Electrodynamics (10 tables), . Educational album of 10 sheets. Electricity, current strength. Resistance. Ohm's law for a circuit section. Dependence of conductor resistance on temperature. Wire connection. EMF. Ohm's law…
SELF-INDUCTION
Each conductor through which electricity flows. current is in its own magnetic field.
When the current strength changes in the conductor, the m.field changes, i.e. the magnetic flux created by this current changes. A change in the magnetic flux leads to the emergence of a vortex el. field and induction emf appears in the circuit. 
This phenomenon is called self-induction.
Self-induction - the phenomenon of the occurrence of EMF induction in email. circuit as a result of a change in current strength.
The resulting emf is called EMF self-induction
Closing the circuit 
When closing in el. the current increases in the circuit, which causes an increase in the magnetic flux in the coil, a vortex electric arises. field directed against the current, i.e. an EMF of self-induction occurs in the coil, which prevents the current from rising in the circuit (the vortex field slows down the electrons).
As a result L1 lights up later, than L2.
Open circuit 
When the electric circuit is opened, the current decreases, there is a decrease in the m.flow in the coil, a vortex electric field appears, directed like a current (tending to maintain the same current strength), i.e. A self-inductive emf appears in the coil, which maintains the current in the circuit.
As a result, L when turned off flashes brightly.
Conclusion
in electrical engineering, the phenomenon of self-induction manifests itself when the circuit is closed (the electric current increases gradually) and when the circuit is opened (the electric current does not disappear immediately).
What does the EMF of self-induction depend on?
Email current creates its own magnetic field. The magnetic flux through the circuit is proportional to the magnetic field induction (Ф ~ B), the induction is proportional to the current strength in the conductor
(B ~ I), therefore the magnetic flux is proportional to the current strength (Ф ~ I).
The EMF of self-induction depends on the rate of change in the current strength in the email. circuits, from the properties of the conductor
(size and shape) and on the relative magnetic permeability of the medium in which the conductor is located.
A physical quantity showing the dependence of the self-induction EMF on the size and shape of the conductor and on the environment in which the conductor is located is called the self-induction coefficient or inductance. 
Inductance - physical. a value numerically equal to the EMF of self-induction that occurs in the circuit when the current strength changes by 1 ampere in 1 second.
Also, the inductance can be calculated by the formula:
where F is the magnetic flux through the circuit, I is the current strength in the circuit.
Inductance units in the SI system:
The inductance of a coil depends on:
the number of turns, the size and shape of the coil, and the relative magnetic permeability of the medium
(possible core).
EMF of self-induction prevents the increase in current strength when the circuit is turned on and the decrease in current strength when the circuit is opened.
Around a conductor with current there is a magnetic field that has energy.
Where does it come from? Current source included in el. chain, has a store of energy.
At the time of closing email. In the circuit, the current source expends part of its energy to overcome the action of the emerging EMF of self-induction. This part of the energy, called the self-energy of the current, goes to the formation of a magnetic field.
The magnetic field energy is own current energy.
The self-energy of the current is numerically equal to the work that the current source must do to overcome the self-induction EMF in order to create a current in the circuit.
The energy of the magnetic field created by the current is directly proportional to the square of the current strength.
Where does the energy of the magnetic field disappear after the current stops? - stands out (when a circuit with a sufficiently large current is opened, a spark or arc may occur)
QUESTIONS FOR THE VERIFICATION WORK
on the topic "Electromagnetic induction"
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1. List 6 ways to obtain an induction current. |
An electric current passing through a conductor creates a magnetic field around it. The magnetic flux Ф through the circuit from this conductor is proportional to the induction module B of the magnetic field inside the circuit, and the magnetic field induction, in turn, is proportional to the current strength in the conductor. Therefore, the magnetic flux through the circuit is directly proportional to the current strength in the circuit:
The coefficient of proportionality between the current strength I in the circuit and the magnetic flux F created by this current is called inductance. The inductance depends on the size and shape of the conductor, on magnetic properties the environment in which the conductor is located.
Unit of inductance.
per unit of inductance in international system accepted henry This unit is determined based on the formula (55.1):
The inductance of the circuit is equal if, with a DC current of 1 A, the magnetic flux through the circuit is
Self-induction.
When the current strength in the coil changes, the magnetic flux created by this current changes. A change in the magnetic flux penetrating the coil should cause the appearance of an induction emf in the coil. The phenomenon of the occurrence of EMF induction in
electric circuit as a result of a change in the current strength in this circuit is called self-induction.
In accordance with the Lenz rule, the EMF of self-induction prevents the increase in current strength when the circuit is turned on and the decrease in current strength when the circuit is turned off.
The phenomenon of self-induction can be observed by assembling an electrical circuit from a coil with a large inductance, a resistor, two identical incandescent lamps and a current source (Fig. 197). The resistor must have the same electrical resistance as well as coil wire. Experience shows that when the circuit is closed, an electric lamp connected in series with a coil lights up somewhat later than a lamp connected in series with a resistor. The increase in current in the coil circuit upon closing is prevented by the self-induction EMF that occurs with an increase in the magnetic flux in the coil. When the power source is turned off, both lamps flash. In this case, the current in the circuit is supported by the EMF of self-induction, which occurs when the magnetic flux in the coil decreases.
EMF of self-induction arising in a coil with inductance according to the law of electromagnetic induction is equal to
The EMF of self-induction is directly proportional to the inductance of the coil and the rate of change of the current strength in the coil.
Using expression (55.3), we can give a second definition of the unit of inductance: an element of an electrical circuit has inductance in if, with a uniform change in the current strength in the circuit by 1 A for 1 s, an EMF of self-induction of 1 V occurs in it.
The energy of the magnetic field.
When the inductor is disconnected from the current source, an incandescent lamp connected in parallel with the coil gives a short flash. The current in the circuit arises under the action of self-induction EMF. The source of energy released in this case in the electrical circuit is the magnetic field of the coil.
The energy of the magnetic field of an inductor can be calculated in the following way. To simplify the calculation, consider the case when, after disconnecting the coil from the source, the current in the circuit decreases with time according to a linear law. In this case, the EMF of self-induction has a constant value equal to
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