The phenomenon of self-induction is the inductance of the energy of the magnetic field YouTube. III. Fundamentals of electrodynamics. Lenz's rule and inductance

The electric current, which passes in a closed circuit, creates a magnetic field in an extremely wide area, part of the line of which interweaves the surface surrounded by the same circuit. In this manner, it appears that the circuit is permeated with a moisture flow. The magnitude of the flow is proportional to the magnitude of the magnetic induction, which is also proportional to the strength of the stream that flows along the circuit. Also, the magnitude of the flow is directly proportional to the strength of the stream.

Ф~I, Ф=LI

proportionality factor L – called circuit inductance.

Inductance depends on the size and shape of the conductor, on the magnetic powers of the medium in which the conductor is located.

Inductance- a scalar physical quantity that is comparable to the magnetic flux that passes through the circuit, with a flow force in the circuit of 1 A.

The result shows that the inductance is numerically lower than the EPC self-inductance that appears in the circuit for changing the power supply by 1 A in 1 s.

Let's connect the circuit to the main stream. At the circuit of the potential difference on the pressure pumps of the jet, the movement of charges begins. The strum near the contour is growing. Also, the circuit suffers from EPC self-induction, which oversteps the increasing flow. The work involved the struma from the EPC self-induction and the installation of the struma when the magnetic field was created.

A magnetic field is also electric and carries energy. The energy of the magnetic field, the ancient work of external forces, prevented EPC self-induction.

Quit 14

Vilny electromagnetic vibrations. Amplitude, frequency and period of kolivan. Kolivanya phase. Energy transformation under the hour of Kolivan.

Kolivannyam is a process in which physical quantities take on new values ​​at regular intervals of an hour.

Kolivannya is characterized by period and frequency.

Period T- The trivality of one knock.

Frequency n- The number of kolivan in one hour.

Harmonious Quantifications are called vibrations in which changes in physical quantities are governed by the law of sine and cosine.

x(t)=Аcos(wt+j 0) or x(t)=Аsin(wt+j 0), where x(t) is the variation of the value that varies depending on the position of the equalizer; A - maximum relief from the position of equal weight or amplitude; w- cyclical or circular frequency, Which is related to the period and frequency of the relationships w=2p/T, w=2pn; j = (wt + j 0) - phase kolivanya, which shows how part of the period of kolivanya begins; j 0 - Cob phase.

Only one in the world[n]=s -1 , [w]=rad/s, [j]=rad.

The electric lance, which consists of an inductance and capacitance coil, is called an oscillating circuit, because it can generate free electromagnetic oscillations.

Voltage electromagnetic vibrations in the circuit– by periodically changing the charge on the capacitor, the current in the circuit and the voltage on both elements of the circuit, which are generated without the addition of energy from external reactors.

Let the initial hour on the capacitor equal the charge q 0, therefore, the voltage on the capacitor, and the energy of the electric field in the middle of the capacitor. Over time, the capacitor begins to discharge. Lanciusia has a strum. The charge of the capacitor, the voltage and the energy of the electric field change. The increase in current in the boiler is due to self-induction in the EPC boiler, so the increase in current and discharge of the capacitor is not caused by mitt, but by the harmonic law.

At the moment of complete discharge of the capacitor, the power of the current and, therefore, the energy of the magnetic field of the coil reaches its maximum value.

So, like a discharge capacitor, the strum begins to change. A change in the strum in the cat causes the appearance of EPC self-induction, which fails to support the falling strum. Therefore, the change in current is not due to the mitt, but due to the harmonic law, in which the capacitor is recharged.

At the moment when the strimus of the lancus is equal to zero, the charge on the capacitor, the voltage and energy of the electric field in the capacitor is maximum. The polarity of the charge of the capacitor plates is identical.

Period of strong electromagnetic disturbances is indicated by Thomson's formula

T = 2pÖLC.

The charge on the capacitor, the flow of the lancer, the voltage on both elements of the circuit changes according to the harmonic law.

q=q 0 coswt; U = U 0 coswt; I=-I 0 sinwt

Residual heat loss every day, then the total energy of the ideal circuit, which is equal to the total energy of the electric field in the capacitor and the magnetic field in the coil, becomes stationary.

W=W ate +W mag =CU 2 /2 + LI 2 /2

At the moment when the stream in the lancet is daylight, all the energy is concentrated in the capacitor and the old CU 2 max/2.

If the capacitor is discharged, all the energy is concentrated in the coil and the old LI 2 max/2.

As a result of strong electromagnetic fluctuations in the circuit, there is a constant transition of electrical energy into magnetic energy and back, during which all the energy is lost permanently.

The culprit of strong colivania in the circuit is due to the phenomenon of self-induction.

Reconversion of the minty strum. Step-down and step-down transformers, their devices and operating principles. Transfer of electrical energy to the stand.

A transformer is an electrical device that is used to transform (increase or decrease) the alternating voltage.

A transformer is made up of two windings - the primary and secondary, which are wound on a carbon core.

The transformer action is connected to the electromagnetic induction field.

An alternating voltage is supplied to the primary winding, which is reversed. The alternating magnetic flow induces self-induction e si in the skin turn of the primary winding of the ERS. Since this magnetic flux, which is clearly visible in the core, practically does not dissipate and penetrates the secondary winding, then EPC induction e i = e si occurs in the skin turn of the secondary winding. The EPC values ​​that occur in the primary and secondary windings are equal to E 1 =n 1 e si and E 2 =n 2 e i similar. Also, the ratio of EPC in the windings is the same as the ratio of the number of turns n1/n2.

The ratio of the number of turns in the first winding to the turns in the second is called the transformation factor k. If k>1, then the transformer is step-down; yakscho k<1, то – повышающий.

The no-load mode of the transformer is the mode with the secondary winding open. Then the voltage on the secondary winding is U 2 = n 2 e i., but in the primary winding U 1 = E 1.

The voltage supply on the primary and secondary windings is the same as the number of turns of these windings U 1 /U 2 =n 1 /n 2 .

The operating mode of a transformer is a mode in which the voltage is switched on in the secondary winding. Then U 2 =Ei- I 2 R winding, where I 2 - Strum that flows at the second winding.

The efficiency factor of daily transformers is 95-99.5%. Energy is wasted through the generation of heat in the windings of the transformer, the dissipation of magnetic flux and the remagnetization of the core.

Transformers are widely used when transmitting electricity over large distances, since heat losses are proportional to the square of the power flow, it is more advantageous to transmit electricity at a small flow.

A transformer is installed at the power station, which moves and changes the power of the stream, and at the substation, when the energy reaches the source, it reduces the transformer.

QUIT 18

Electromagnetic and quantum theories of light. Planck's formula. Corpuscular-Hvilian dualism. Energy, momentum and mass of a photon.

After the creation of the electromagnetic theory, Maxwell realized that the speed of expansion of light in a vacuum is avoided by the speed of expansion of electromagnetic coils. He proposed a hypothesis about the electromagnetic nature of the light, which was confirmed by research. This is consistent with the electromagnetic theory of light, whether it is light vibration or electromagnetic coils. The frequency of light signals is in the interval from 41014 to 7.51014 Hz.

Khvil's theory explained well the phenomena connected with the expansion of the light. For example, interference, diffraction, polarization, vibration, distortion. However, the phenomena associated with the interaction of light with speech, with the proliferation and polishing of light, cannot be explained on the basis of this theory.

Max Planck assumed that the light appears not in the appearance of strength, but in the appearance of songful and inseparable portions of energy, which he called quanta .

The smallest portion of energy that is not transmitted by frequency n is calculated using Planck’s formula

de h = 6.63 10 -34 J s - constant Planck, = 1.05 10 -34 J s, n i w - frequency and cyclic frequency of vibration.

Developing Planck's theory, Einstein discovered that the light spreads and fades in small portions, then. The light that spreads everywhere is a “collection” of earthy elementary particles – photons . This is how it was created quantum theory of light .

Plan - lesson summary

« Self-induction . І inductivity . Magnetic field energy struma"

Vikonala 5th year student

groupie FM-112

full-time training

physics and mathematics

Kezhutina Olga Vladislavivna

Date: 09/23/16

Volodymyr 2016

Lesson topic: Self-induction . І inductivity .

Class: "11b"

Lesson type : lesson of acquiring new knowledge.

Lesson overview: lesson-lecture.

Purpose : formulate statements about those that changing the force or flow in the conductor creates a whirlwind will, which can either speed up or galvanize electronics that collapse; formulate statements about the energy of the electric current in the conductor and the energy of the magnetic field created by the current.

Zavdannya:

Osvitny: Repeat the students' knowledge about the phenomenon of electromagnetic induction, cover them; On this basis, we can understand the phenomenon of self-induction. Learn to learn the law of electromagnetic induction and explain the phenomenon.Enter a formula for the breakdown of the energy of the magnetic field and the concept of the electromagnetic field.

Vikhovny: Develop interest in the subject, practise, and respectfully evaluate the types of friends, work wisely collectively and in pairs.

Developing: Development of the physical mentality of students, expansion of the conceptual apparatus of students, development of ability to analyze information, work on observations and investigations.

Obladnannya:

Lesson heading:

11.20 – 11.21

Hello, guys, sit down.

Learn to prepare for the lesson.

Updating knowledge.

11.22-11.28

Checking the homework, if there is food in school, then we sort them out.

Frontal feeding:

Should the field be called a vortex electric field?

What is the core of the vortex field?

What is Foucault's strumi? Point the butts of this vikoristan.

Where does the EPC induction lie, what arises from the conductor, what collapses in the changing magnetic field?

Students check their homework and confirm the supply:

The field that will give rise tochanges in the hour, magnetic field.

Magnetic field that changes hourly.

Inductive streams that reach massive conductors of great numerical value through those whose supports are few.

The fluidity of the conductor in a uniform magnetic field.

Healthy meals:

4. Guess the formula that can be used to find the EPC induction in conductors that collapse.

Motivational stage.

11.29-11.31

The foundations of electrodynamics were laid by Ampere in 1820. Ampere's work inspired many engineers to design various technical devices, such as an electric motor (designer B. S. Jacobi), a telegraph (S. Morse), an electromagnet, which was designed following the American opinion of Henry.

Joseph Henry has become famous for his creation of a series of unique pressure electromagnets with a lifting force of 30 to 1500 kg per 10 kg magnet weight. The creation of electromagnetism, 1832, a new phenomenon in electromagnetism was discovered - the phenomenon of self-induction. To whom I will reveal this lesson.

Recording topics on doshtsi: “ Self-induction . І inductivity . Energy of the magnetic field ».

Development of new material.

11.32-11.45

Henry wines flat cats from smoky medium, for the help of some powerful effects expressed brighter, lower with the vikoristan of fragrant solenoids. I really appreciate that when there is a strained cat in the lance, the strum in this lance reaches its maximum value much more, even without the cat.

Dosvid: The little one shows the electrical diagram of the experimental setup, on the basis of which the phenomenon of self-induction can be demonstrated. The electric lamp consists of two parallel-connected light bulbs, connected via a key to a permanent source. A coil is connected in series with one light bulb. After the lance closes, it is clear that the light bulb, which is connected in series with the coil, burns more than the other light bulb.

When the lamp is turned on, the light bulb is connected in series with the coil, and the light bulb goes out.

Let's take a look at the processes that occur in this circuit when the key is closed or open.

1. The key is stuck.

The lancus has a thread-conducting coil. Stop the flow of the thread from flowing in front of the anniversary arrow. Then the magnetic field will be directed towards the mountain.

In this way, a coil appears in the expanse of a strong magnetic field. When the flow grows, the coil ends up in the vastness of the magnetic field of the current flow, which changes. As the stream grows, the magnetic flow of the creations with this strum also grows. Apparently, with an increase in the magnetic flux that penetrates the surface of the circuit, in which circuit the electrically destructive inductive force arises and, as a result, the inductive stream. According to Lenz's rule, this stream will be straightened in such a way that its magnetic field will overcome changes in the magnetic flux that penetrates the plane of the circuit.

So, for the examined little one, 4 turns of the inductive flow are due to the directions behind the year arrow, thereby overriding the growth of the power flow of the turn. Also, when the key is closed, the stream at the lancet does not grow, due to the fact that the inductive stream is to blame in the lancet, which causes harm, straightening at the proximal side.

2. Rozmikannya key.

When the key is opened, the strings at the lancus change, which leads to a change in the magnetic flux across the plane of the turn. Change the magnetic flux until EPC induction and inductive flow appear. In this type, the inductive flow of straightening has the same effect as the damp flow of the coil. This leads to an increase in the change in the blood flow.

Visnovok: when changing the current in the conductor, electromagnetic induction occurs in this conductor, which generates an inductive current, straightening in such a way as to override any change in the current in the conductor . This is the essence of the phenomenon of self-induction. Self-induction is the result of electromagnetic induction.

Self-induction - This is the result of electromagnetic induction in the conductor when changing the power of the stream that flows through this conductor.

Inductance. The module of the induction vector of the magnetic field created by the stream, proportional to the strength of the stream. Since the magnetic flux F is proportional, then F ~ B ~ I.

You can, otzhe, sverdzhuvati, scho

Ф = LI,

where L is the proportionality coefficient between the flow of the conductive circuit and the magnetic flux.

The value L is called the inductance of the circuit, and its self-induction coefficient.

Vikorist's law of electromagnetic induction and elimination of viraz, is irreducible

From the formula it vips, schoInductance is a physical quantity, numerically equal to EPC self-induction, which appears in the circuit for changes in the power flow in the current by 1 A in 1 s.

Inductance, like electrical capacity, depends on geometric factors: the size of the conductor and its shape, but not on the strength of the conductor. Despite the geometry of the conductor, the inductance depends on the magnetic powers of the medium in which the conductor is located.

Obviously, the inductance of one small turn is less than that of the coil (solenoid), which is the sum of N similar turns, since the magnetic flux of the coil increases N times.

The unit of inductance in CI is called henri (indicated by Gn). The inductance of the conductor is equal to 1 H, since in this case, with a uniform change in power, the flow of 1 A per 1 volt results in EPC self-inductance of 1 V:

People are faced with the phenomenon of self-induction every day. Right now, by turning on the light, we ourselves are closing or releasing the lance, which causes inductive jets to arouse. Sometimes these jets can reach such great magnitudes that a spark jumps in the middle of the jet, which can hurt us.

Analogy between self-induction and inertia. The phenomenon of self-induction is similar to the phenomenon of inertia in mechanics. Thus, the inertia leads to the point where, under the action of force, the body does not immediately develop a singing fluidity, but step by step. The body cannot be galvanized by mittevo, no matter how great the power of galmivna. So, due to the very effect of self-induction when the lance is closed, the strength of the strum does not immediately acquire a melodic significance, but increases step by step. Vimikayuchi dzherelo, we do not apply strum odrazu. Self-induction continues every day, regardless of Lanzug’s assumption.

To create an electric current and, therefore, a magnetic field, it is necessary to defeat the robot against the forces of the electric vortex field. This robot (due to the law of conservation of energy) is based on the traditional energy of an electric current or the energy of a magnetic field.

Write down the energy strumaI, flow lance with inductanceL, That is, for the energy of the magnetic field of the stream, an analogy between inertia and self-induction can be used.

Since self-induction is similar to inertia, then inductance in the process of creation plays the same role as mass due to increased fluidity in the mechanism. The role of body fluidity in electrodynamics is played by the force of the current as a quantity that characterizes the flow of electric charges.

This energy flow can be influenced by the value of similar kinetic energy in the mechanism:

The energy of the magnetic field flows.

They provide food, enter into discussions, make notes, take notes from the sewers.

Securing the screwed material

11.46-11.56

Promonizes the verse:

There is a misfortune between the children and the localities.

Suitability of pouches. Homework.

11.57-11.58

The icon is displayed and lined. A record of what was discussed at home.

D/Z: §14-16, No. 932, 934, 938.

Record homework

Reflection

11.59-12.00

The lesson is organized in such a way that the participants reflect on their actions during the lesson.

Feeding:

1. What new things did you learn in class?

2. What kind of material did you use for the lesson?

3. Have you received a lesson?

Take fate from Rozmov

№931. What is the inductance of the circuit, what is the power of the stream 5 And who is responsible for the magnetic flux of 0.5 mWb?

№933. Find the inductance of the conductor in which, for a uniform change in the power of a 2 A current of 0.25 s, an EPC of self-induction of 20 mV is generated.

№937. A cathode has an inductance of 0.6 H and a flow force equal to 20 A. What is the energy of the magnetic field of this coil? How will the energy of the field change if the strength of the stream changes twice?

№939. Find the energy of the magnetic field of the solenoid, which has a current of 10 A and a magnetic flux of 0.5 Wb.

№932. What magnetic flux arises from a circuit with an inductance of 0.2 mH at a flow force of 10 A?

№934. What type of EPC is generated by self-induction in the winding of an electromagnet with an inductance of 0.4 H for a uniform change in the power flow in it by 5 A in 0.02 s?

№938. What is the force of the flow in the winding of the throttle with an inductance of 0.5 H, so that the field energy reaches 1 J?

STATE AUTONOMOUS PROFESSIONAL INVESTMENT MORTGAGE

NOVOSIBIRSK REGION

"BARABINSKY MEDICAL COLLEGE"

Looked at at the meeting

CMK ODSED

Protocol No.___________

dated ____________ 2018

CMC head

Khritankova N. Yu.

______________________

(Subscription)

METHODICAL GROWTH

COMBINED ACTIVITY FOR Vikladach

Specialty 02/34/01 Nursing on the right (with basic training)

Discipline: “Physics”

Section 3 Electrodynamics. Kolivannya and hvili. Optics

Rozrobnik – depositor Vashurina T.V.

Vytyag with work programs of the discipline “Physics”

for specialty 02/34/01 Sister on the right (with basic training)

METHOD SHEET

Type of activity: combinations lesson.

Type of activity: conversation, explanation with demonstration of personal assistants, top task

Trivalism: 90 hvilin.

OBJECTIVES OF ACTIVITY

Initial goals: formulate statements about the role of physics in the current scientific picture of the world; understanding of the physical essence of the world's monitoring of phenomena through the understanding of the concept of self-induction, inductance, EPC self-induction, magnetic field energy; Accept the formation of the Volodymyr with basic physical concepts, and become familiar with physical terminology and symbolism. Assemble the molding process, organize the power activity, select typical methods and methods for obtaining rights (OK 2).

Development goals: develop interest in the future profession, the understanding of the essence and social significance (OK 1), accept the molding and physical tasks.

Supreme goals: embrace the development of communicative skills; create minds for the development of fluidity and processing of information and language culture; formulate and work with the team (OK 6).

Methods of Navchannya: explanatory and illustrative with the use of information technologies, reproductive

Venue: college auditorium.

MOTIVATION

Topic 3.14 “Self-induction. Inductance. EPC self-induction. Energy of the magnetic field" is included in the program from the initial discipline "Physics" and takes an important place, because The knowledge that is given by the necessary learning of a wealth of topics, both within the framework of physics programs and also in related disciplines (chemistry, mathematics). The disadvantage of working with electrical devices lies in the fact that the current, magnetic field, current and voltage do not produce any external signs that would allow people to use their sense organs (sight, hearing, smell) to detect the danger that threatens and the presence of others coming in

During the course of employment there will be 2 initial years. During the combined lesson, the knowledge of the form of oral training is updated, by checking the excess knowledge necessary for the new material; thorough application of new material; The first priority is to consolidate new material to further solve problems on this topic. Control of the level of mastery of new material is carried out in accordance with the testing of students. Skin awareness people need to continuously update their knowledge of physics, develop interest in their future profession, understand the reality and social significance (OK 1), learn to organize their brightness, note the methods and methods of defining the task and then evaluate their brightness (OK2), and It is also necessary for a future medical practitioner to learn how to work with a team (OK6).

APPLIED CHRONOCARD OF COMBINED WORK

BREAKING MATERIAL

Plan for the publication of initial material on the topic

“Self-induction. Inductance. EPC self-induction. Magnetic field energy".

Self-induction.

Inductance.

EPC self-induction.

Magnetic field energy.

1. Self-induction- evidence of EPC induction in the wire circuit due to changes in the current flow. The EPC, which is responsible for this, is called EPC self-induction.

Showing signs of self-induction.

Zamikannya Lanzug. When the electric lance is shortened, a stream increases, which causes an increase in the magnetic flux from the coil, and an eddy electric field arises, straight against the strum, then. In the cat, the EPC is due to self-induction, which crosses the accumulating stream in the lancus (the vortex field galvanizes the electrons).

As a result L1 sleep later, lower L2.

Rozmikannya Lanzyuga.

When the electric lance is disconnected, the string changes, a change in the magnetic flux in the coil occurs, and the vortex electric field arises, straightened like the string (in order to save the excessive force of the string), etc. In the cat, the EPC is due to self-induction, which encourages struma in the Lancus. As a result, L, when hit, burns brightly.

2.Inductance, and the coefficient of self-induction is a parameter of the electric lance, which means the EPC of self-induction that is introduced into the lance when changing the stream that flows through it, or (i) deformation. The term "inductance" also refers to the coil of self-induction, which means the inductive power of Lanzug.

Inductance- physical quantity, numerically equal to EPC self-induction, which appears in the circuit for a change in the power flow by 1 A in 1 s.

F – magnetic flux through the circuit, I – flow force in the circuit.

Inductance unit at CI Henry(Gn): [L] = [ ] = []= Gn; 1 Gn = 1
.

Inductance, as well as electrical capacity, depends on the geometry of the conductor - its size and shape, rather than depending on the strength of the conductor. In addition, the inductance lies in the magnetic powers of the middle, which contains the conductor.

Coil inductance stay in:

− number of turns,

− size and shape of the cat;

− type of aqueous magnetic penetration of the middle (possible core).

Strumi zamikannya and rozmikannya.

Whenever it is turned on, the viscous struma in the lancinus must beware of this name extra currents of self-induction (extra currents of fusion and dissolution), What arises in Lancus as a result of symptoms of self-induction and changes (similarly to Lenz’s rule) the rise and fall of struma in Lancus. Inductance characterizes the inertia of a lance in relation to a change in its flow, and it can be seen as an electrodynamic analogue of body mass in a mechanism, which is the world of body inertia. In this case, the force of the stream plays the role of fluidity of the body.

3. EPC self-induction.

Self-induction - blame for EPC induction in the wire circuit due to changes in the new power supply. EPC induction is due to changes in magnetic flux. If this change reverberates with a powerful stream, then talk about EPC self-induction :

ε is =–
= -L ,

de L- inductance of the circuit, or self-induction coefficient.

4. The energy of the magnetic field is strum.

We know the energy that flows electricity to the conductor. In accordance with the law of conservation of energy, the energy of the magnetic field created by the struma is the same energy that can be used up in the core (galvanic element, generator at a power plant, etc.) to create the struma. When the stream is applied, this energy is seen in one or another form.

It is clear that in order to create a stream it is necessary to expend energy, in order to create a robot. It is explained that when the lancet is closed, when the strum begins to grow, the conductor has a vortex electric field, which acts against the electric field, which is created in the conductor as a result of the electric strum. In order for the force of the strum to become equal to I, it is necessary to work against the forces of the vortex field. This robot generates an increase in the energy of the magnetic field of the stream.

When the lancet is opened, the stream becomes aware and the vortex field produces a positive effect. The energy stored in the strum is visible. This is revealed by a strong spark that occurs when the lance opens with high inductance.

It is possible to write down the expression for the energy struma I, the flow lance with inductance L, (the same for the energy of the magnetic field struma), using the analogy between inertia and self-induction, as stated above.

Since self-induction is similar to inertia, then inductance in the process of creation can play the same role as mass due to the increased fluidity of the body in mechanics. The role of body fluidity in electrodynamics is played by the force of the current I as a quantity that characterizes the flow of electric charges.

If this is so, then the energy of the stream W m can be taken into account by a value similar to the kinetic energy of the body
at the mechanism, and write down at the sight W m =
(**).

This very expression of energy flows out as a result of degeneration.

The energy of the strum (**) is expressed through the geometric characteristic of the conductor L and the force of the strum in the new I. This energy can also be expressed through the characteristics of the field. Calculations show that the strength of the magnetic field energy (that is, the energy of a unit volume) is proportional to the square of the magnetic induction, just as the strength of the electric field energy is proportional to the square of springiness of the electric field.

A magnetic field created by an electric current has energy directly proportional to the square of the current's strength.

Basic formulas:

Faraday's law(Law of electromagnetic induction): ε = -
,De ΔФ - change in magnetic flux, Δt - time interval during which this change occurred.

The phenomenon of self-induction lies for those who, when changing the struma in the lancus, EPC occurs, which counteracts this change.

Magnetic flux F through the surface, surrounded by a contour, directly proportional to the force of the stream I contour: Ф = LI,

de L - Proportionality coefficient, grades of inductance.

EPC self-induction is expressed through a change in the strength of the struma in the lancus ΔI by the offensive formula:

ε = -
= -L where Δt is the hour during which the change took place.

Magnetic field energy W is expressed by the formula: W=

SUPPLEMENT No. 1

CONTROL OF KNOWLEDGE ON ADVANCED TOPICS (basic)

“Lenz's rule. Whirlwind jets. Maxwell's electromagnetic theory"

Lenz's rule.

Vіdpovid: Faraday experimentally established that when changing the magnetic flux in a wire circuit, EPC induction occurs, which is the same as the previous rate of change of magnetic flux through the surface surrounded by a contour taken from the minus sign:

This formula is called Faraday's law.

Evidence shows that the inductive stream, which is generated in a closed loop when the magnetic flux changes, is immediately rectified so that the magnetic field that is created jumps the change in the magnetic flux, causing a surge є induction jet. The rule, formulated in 1833, is called Lenz’s rule.

Small 1 illustrates Lenz’s rule in the case of an unbreakable wire circuit, which in a uniform magnetic field, the induction modulus of which increases over time.

Lenz's rule contradicts the experimental fact that the opposite signs appear (the minus sign in Faraday's formula). Lenz's rule has deep physical meaning - it expresses the law of conservation of energy.

Lenz's rule (Lenz's law) was installed by Ege. X. Lenz 1834 b. This clarifies the law of electromagnetic induction, published in 1831. M. Faraday. Lenz's rule determines the direction of the induction stream in a closed loop when it is in an external magnetic field.

The direction of the inductive stream is always such that it is possible to try to use it on the side of the magnetic field, to push against the flow of the circuit, and to create a magnetic flow with this stream. Fi to compensate for changes in external magnetic flux Fe.

Lenz's law is the expression of the law of conservation of energy for electromagnetic components. Diyno, under the Russian closed contour in the magnate half for the Rahunovs of Cindlear forces, the forces of the force of the force of the forces, the vinica in the result of the mutual struggle of the magnete field of the hidden rukhu.

Lenz's rule is illustrated by the little ones:

When a permanent magnet is inserted into a coil closed to a galvanometer, the inductive current in the coil is such that it creates a magnetic field with a vector IN", straighten along to the field induction vector of the magnet U, tobto vishtovhuvatime magnet from the cat or pereshkodzhatime yogo ruhu. When the magnet is drawn from the coil, the field, created by the inductive stream, attracts the coil, so that it again jumps over the handle.

It is practical to describe the algorithm for stagnating Lenz's rule.

Subject: To apply the Lenz rule using the method of determining the direct inductive flow Ie The circuit must adhere to the following recommendations:

1. Set the direction of the line magnetic induction of the external magnetic field.

2. Understand that the flow of magnetic induction of this field through the surface surrounded by a contour increases ( ΔФ 0), or it changes ( ΔФ

3. Set the direction of the linear magnetic induction of the magnetic field of the induction stream Ii. These lines run straight, according to Lenz’s rule, along the lines, as ΔФ 0, and my mother contacted them directly, because ΔФ

4. Knowing the direction of the line magnetic induction, mean the direction of the induction stream Ii, cringing drill rule.

3. What are the reasons for the change in magnetic flux (2 individuals provide evidence).

Subject: A change in the magnetic flux that passes through a closed loop can occur for two reasons.

1. The magnetic flux changes as a result of the movement of the circuit or its parts in a stationary magnetic field. This happens when the conductors, and at the same time those carrying a charge, collapse in the magnetic field. The culprit of EPC induction is explained by the effect of the Lorentz force on voltage charges in conductors that collapse. The Lorentz force always plays the role of an external force.

Let us look at how the EPC induction occurs in a rectangular circuit placed in a uniform magnetic field perpendicular to the plane of the circuit. Place one of the sides on the contour evenly and go smoothly along the other two sides (Fig. 2).

On the free charge, the Lorentz force acts on this circuit. One of the storage forces, connected to the portable liquidity of the charges, is directly connected to the conductor. The storage area is shown in Fig. 1.20.3. Vaughn plays the role of an outside force. This module is old

For the EPC funds

In other indestructible parts of the circuit, the external force is equal to zero. A synonym for this can be given a similar look. In an hour Δt the area of ​​the contour changes to ΔS = lυΔt. The change in magnetic flux over an hour is greater than ΔΦ = BlυΔt. Otje,

In order to set a sign in the formula that connects and it is necessary to choose between themselves the rule of the right drill, direct normal and positive, direct bypass the contour, as shown in Fig. 1.20.1 and 1.20.2. Once you have done this, it is easy to follow Faraday's formula.

Since the base of every lance is older than R, then the inductive stream flows along a new one, which is older. For an hour Δt, Joule heat is visible on the support R

The food is at fault: this energy comes from the stars, and even the Lorentz force does not stop the robot! This paradox arises through those who created the robot without Lorentz’s storage force alone. When an inductive stream flows through a conductor that is in a magnetic field, another Lorentz shear force is applied to the high charges, which is associated with the aqueous fluid of the charge of the conductor. This warehouse is responsible for the appearance of ampere power. For the vipadku shown in Fig. 1.20.3 power module Ampere is old FA = I B l. The power of Ampere is directly directed towards the conductor's hand; That's why there is negative mechanical work. In an hour Δt this robot Amech is more expensive

A conductor that collapses in a magnetic field through which an inductive stream flows experiences magnetic galvanization. The entire Lorentz force is equal to zero. Joule heat in the circuit is seen either due to the effect of external force, which keeps the fluidity of the conductor constant, or due to the change in the kinetic energy of the conductor.

2. Another reason for a change in the magnetic flux that passes through the circuit is a change in the magnetic field during an unbroken circuit. And here the fault of EPC induction cannot be explained by the action of the Lorentz force. Electronics in an indestructible conductor can only be destroyed by an electric field. This electric field is generated by a magnetic field, which changes over time. The operation of this field when moving a single positive charge in a closed circuit results in traditional EPC induction in an indestructible conductor. However, the electric field generated by the magnetic field, which changes, is not potential. It is called a vortex electric field. The concept of the vortex electric field was introduced to physics by the great English physicist James Maxwell in 1861.

4. Describe the causes of electromagnetic induction in undamaged conductors.

Vіdpovid: The phenomenon of electromagnetic induction in indestructible conductors, which occurs when changing an excessive magnetic field, is also described by Faraday’s formula. Thus, the phenomena of induction in the dry and non-ruined conductors proceed in the same way, but the physical reason for the occurrence of the inductive stream appears differently in these two types: in the type of EPC conductors, There are inductions inspired by the Lorentz force; In case of unbreakable EPC conductors, induction is due to the strong charges of the vortex electric field, which arises when the magnetic field changes.

Subject:

In Russia.

In an electric motor, when a stream is passed through, a moment appears that turns

The first electric motor designed by Jacobi (1836).

Closed strumas that arise from strong conductive midstreams are called eddy strumas or Foucault's strums- in the name of the French scientist, who is out of their depth. Foucault currents can be either weak (in the cores of transformers, parts of generators and engines that are wrapped in Foucault jets during heating), or short (in induction furnaces for melting metals or preparing liquids). In this case, the body to conduct (metal or hedgehog) actually plays the role of the core. It is placed in the middle of the coil, through which an alternating high-frequency stream is passed, which generates an alternating magnetic field in the middle of the coil. And then the law of electromagnetic induction “works”. The changing magnetic field causes the appearance of Foucault inductive streams, which heat up the body to be carried out.

6. Describe the main theses of Maxwell’s electromagnetic theory.

Subject: Maxwell's theory is a consistent theory of a single electromagnetic field, which is created by a sufficient system of electric charges and streams. Maxwell’s theory is based on the basic principles of electrodynamics: based on a given distribution of charges and flows, the characteristics of the electric and magnetic fields they create are calculated. Maxwell's theory is a statement of the most important laws that describe electrical and magnetic fields: Gauss's theorem, the law of constant flow, the law of electromagnetic induction.

This theory does not consider the internal mechanism of the objects that appear in the middle and cause the appearance of electric and magnetic fields. The core is to describe the pre -person of the TROOX of the quantities, to set it to the magnitic power of the power: the vice of the penetration of the penetration of the penetration of the Pitoma Eleknodist.

Macroscopic fields are seen that are created by macroscopic charges and strumas, including a wide range of atoms and molecules. Stand up from the river fields to the visible points of the expanse, which is richer than the linear dimensions of atoms and molecules. Therefore, macroscopic fields vary significantly from areas of many large sizes of atoms.

Macroscopic charges and streams are a combination of microscopic charges and streams that create their own electric and magnetic microfields. These microfields constantly change over time at every point in the space. Macroscopic fields are averaged microfields.

Maxwell's theory is a theory of proximity, due to which electrical and magnetic interactions occur in the form of an electromagnetic field and expand from the end fluid, which is similar to traditional fluid light in whose middle.

Evaluation criteria:

Rating 5" - on the delivery of the supply, the student gave a re-ignited confirmation and reinforcement on the additional supply;

Rating “4” - at the given supply, the student gave a renewed testimony, but did not confirm the additional supply;

Rating “3” - the student gave the wrong answer to the question and did not lose the answer to the additional question;

Rating “2” – not confirmed on the power supply.

SUPPLEMENT No. 2

TASKS FOR CONSOLIDATION AND SYSTEMATIZATION OF NEW KNOWLEDGE(in writing, not evaluated)

Physics 11 Different independent and control robots A. Kirik Store. 10 Middle rhubarb No. 1-6.

Details of reports before assignment for consolidation and systematization

SUPPLEMENT No. 3

TASK FOR ADVANCE CONTROL KNOWLEDGE

(Definitely, not evaluated. Etalons of nutritional inputs for advanced control are located in the output material)

Give proper self-induction.

Describe the symptoms of this phenomenon.

Formulate the meaning of inductance.

Which units exhibit inductance?

Which parameters should this value be stored in?

What formula describes the energy of the magnetic field?

SUPPLEMENT No. 4

CONTROL MATERIAL (written)

Test

What phenomenon is called self-induction?

A) evidence of EPC induction in the wire circuit

B) physical quantity, numerically equal to EPC self-induction

C) the manifestation of EPC induction in the circuit, what should be done when changing the current circuit

D) the phenomenon of faulty electrical flow in the wire circuit

What quantity is called inductance?

A) flow of magnetic induction through the surface surrounded by a contour

B) a physical quantity, numerically equal to the EPC self-induction, which appears in the circuit when the power supply changes by 1 A in 1 s.

B) physical quantity, numerically equal to EPC self-induction

3. What is the name of the unit of magnetic inductance?

4. What formula is used to calculate the energy of a magnetic field?

A) W =

B) ε = -
,

How will the energy of the magnetic field change so that the force of the stream in the lancus increases by 2 times?

A) don’t change

B) change 2 times

C) increase 4 times

How will the energy of the magnetic field change if the inductance of the circuit changes by 2 times?

A) change 4 times

B) increase 2 times

C) don’t change

D) change 2 times

Details of reports prior to the delivery of control material:

Evaluation criteria:

for 4 correct answers – “3” points;

for 5 correct answers – “4” points;

for 6 correct answers – 5 points.

ACTIVITY FOR STUDENTS' INDIVIDUAL POST-CLASSROOM WORK

Purpose: It is important to provide information for the student’s independent work and increase respect for important moments.

Hour for the Vikonannya Zavdannya: 45 hvilin.

G. Ya. Myakishev, B. B. Bukhovtsev, N. N. Sotsky, Physics. 11th grade Handpiece for backlighting installations (with an accessory on the electronic nose). Basic and profile regions - M.: Prosvitnitstvo, 2011, p. 43-48, paragraphs 15-17, read, summary; With. 50 exercises 2 (4).

Evaluation criteria:

student learning notes - “3” bali;

the student, having read the paragraphs and taken notes, received information from his assistant – “4” points;

The student has read the notes, receives information from the assistant, and has completed his assignment – ​​“5” points.

LIST OF VIKORISTANIH JEREL

Info lesson Introduction to the lesson

Inductance is the ratio of the proportion between the electric current that flows through a closed circuit and the magnetic flux through the surface surrounded by the circuit.

The mathematical formula that illustrates this result:

de F - magnetic flux,

L - inductance,

I – strum strength.

This is a classic inductance, take the initial stage of development of electromagnetic fields. One of the manifestations of inductance has been displayed. Having learned from it, you might think that inductance is the property of a small class of objects, some closed circuits, that create a magnetic field. Not so; show different inductances, and we interact with them in everyday life, often without anyone’s awareness.

In the 19th century, electromagnetic boxes began to be built. The concept of inductance, as a special component of an electrically conductive circuit, was formulated in 1886 for a steady flow.

Lenz's rule and inductance

An electric stream creates a magnetic field – this was a sensation in the 19th century. In the past, electrical and magnetic components were very different, and the discovery of connections between them aroused the keen interest of the followers. The magnetic field was given over to a large number of powerful, completely different objects – a piece of magnetic ore, the Earth’s core and… ore and strum. It is clear that in the skin of these objects, a magnetic field is generated by the flow of an electric charge.

Current science has established the underground nature of electric and magnetic fields. When a stationary strum was implanted, the first crust was broken until the value of the truth was understood - there was a clear connection between the strum and the magnetic field, between the strength of the strum and the force of the magnetic field created by it.

Symbol L How is inductance meant, in honor of the physicist Emil Lenz. There are magnetic boxes that turn off when the electric current flows. The Lenz force is the force that acts on a conductor behind a stream placed in a magnetic field.

Lenz also watched as coils from electrical wires, which passed through the wires, were attracted or moved, like permanent magnets. How hard is it to do? This was indicated directly by the coils, mutually rotating the coils. And the strength of the interaction was determined by the number of turns and the strength of the flow. With a new flow, the coil with a large number of turns created a larger magnetic field.

Circuit with strum and inductors

The circuit with the string can be single (single-wire coil)

The contour with the strum can be folded from several contours (rich-turn coil)

Electrical and radio equipment will have a lot of coils.

The more turns, the greater the inductance of the coil. The same stream that flows through a single turn and through a rich-turn coil creates a magnetic field of varying strength. A multi-turn coil has a higher inductance than one turn; It is proportional to the number of turns.

If you need to create a strong magnetic field, wind hundreds and thousands of turns from a thin copper wire. Such coils are used in electromagnets, transformers, and electric motors.

Inductance, induction, self-induction

How to designate inductance L chosen in honor of the physicist Lenz, then the unit of the world of inductance Henry (Hn) bears the name of another physicist - Joseph Henry.

Lenz followed the magnetic manifestations that were responsible for the evidence of a stationary strum, and Henry took up the changeable strum. More precisely, we looked at the transient processes that occur when the electric power supply is turned on.

What happens when the strum at the Lancus, which places the inductance coil, turns on? The wine does not increase gradually, but increases smoothly. The more turns the coil has, the more extended the process of growth of the string is. However, the number of turns also contributes to the strength of the magnetic field created by the cat’s strum!

Joseph Henry put together a bunch of boxes. It turns out that the greater the inductance, the greater the inertial process of growth of the flow when turned on. This can be compared with mass in mechanics: the more massive the body, the more powerful it will be when exerting more force.

Why is there more strum in the kotushka? We are wary of self-induction here. Aje strum creates a magnetic field, isn't it?

But the transformation of the fields does not stop. The magnetic field that changes creates an electric field! If there is a conductor near the field, the electrical power is induced in him. This is called electromagnetic induction.

The most alternating, alternating magnetic field will create an electric field and induce an electric current at the conductor.

After clicking on Wimikac, the following processes occur in the Lancer:

1. It appears that the electric current begins to grow stronger;
2. The growing electric current creates a weak magnetic field;
3. The alternating magnetic field in the same conductor induces an electric voltage similar to the applied one;
4. The electrodestroying force induced by the magnetic field is parallel to the voltage from the dzherel, changes the total voltage that acts on the lance, and the strum corresponds to the changed voltage.

The voltage induced by the magnetic field at the conductor is called EPC self-induction. A strum in a conductor is the cause of prostatic tension in the same conductor, while the cause of galvanization of a strum is the strum itself; This process is called self-induction.

The value of EPC self-induction depends on the fluidity of the flow change and the type of inductance:

The minus in the formula indicates that in Lancus it is against the EPC, it is straightened so as to galvanize the change in the strum.

Following this formula, the unit of inductance 1 Henry was calculated as follows:

One Henry is the inductance, at which the speed of changing the flow, which is equivalent to one ampere per second, leads to the induction of self-induction EPC, which is equivalent to one volt.

1 Volt = - 1 Henry * 1 Ampere/second, or

1V = - 1 H * 1A / s

Inductance as a world of self-induction is more easily subject to change, but inductance as a coefficient between flow and magnetic flux. For the discovery of the phenomenon of self-induction, physicists assigned the name of Joseph Henry to the one of the world of inductance.

Magnetic field energy

A magnetic field contains energy. Magnetic forces act on mechanical work, attracting either other magnets or the bodies of magnetic materials. The magnetic field that changes induces an electric current in the conductors.

Magnetic energy can be expressed through a mathematical formula. In the first section, the inertia of the inductive lance was understood, and the role of electromagnetic fields was equal to the role of mass in the mechanism. It’s cool that this analogy fades when we look at energy.

The formula for the energy of a magnetic field is similar to the formula for the kinetic energy of a mechanical body:

The energy of the magnetic field is proportional to the inductance and the square of the value of the stream.

During the transition process, when the strings of the lancer increase significantly when the stream is turned on, there is an accumulation of magnetic energy. This energy can be used for robots. This energy creates problems when the stream is turned on in the Lancus with high inductance.

If the strum is changed, the EPC will change the strum. If you turn on the string, sharply opening the lance, the speed of changing the string from a specific value to zero is theoretically infinitely large. This means that the EPC of self-induction when the stream is turned off can still be infinitely large.

This mathematical paradox arises through simplified, idealized formulas. In fact, the flow is not applied to the mitt, opening the contacts takes only a short period of an hour, but, however, the fluidity of changing the flow is high, and the EPC of a significant value is induced. The most important thing when the lance is turned off is the spark plug. If the lancet's strum is mixed with high inductance, a sharp application of the strum can cause an electric arc to burn out.

What happens if the arc doesn’t break and the strut kicks in? Where did the energy of the magnetic field go? Often the thermal energy was transferred - the contacts of the vimikach got hot. When the energy of the magnetic field suddenly changed to zero, it turned into an electromagnetic field. The alternating magnetic field induced an alternating electric field; from its own earth, the great electric one cried out for a new magnetic coil, and so on.

Viknenny struma forgive the clatter of vimikach - sends a wide “noise” spectrum of electromagnetic sounds into the infinite space.

Direct blowing - inductance is lost

Initially, inductance was considered an attribute of the circuit of the cat. The reason for this is in the ways of vimiru. The magnetic flow through the circuit or the coil is localized, and it can be measured (although the accuracy of the measurement is low). If the coil is untwisted and the wire is straightened, and the current is passed through a straight line, the magnetic field, however, does not change. It’s not easy to control your flow!

What happens from self-induction? The strum of the direct drota grows more rapidly, and the lower one of the kotushka. If the wire is stretched for several kilometers (like a power line), then self-induction must be avoided. The growth of the stream when it is fed into the transmission line is not generated. This means that direct conduction has inductance, although less.

On the small readings, the conductor with the strum and the power lines of the magnetic field that form the shape of the ring.

Inductance and reactive support

The inductance coil can only provide minor support to a stationary current, but not significantly to support a variable current. Such an operation is called reactive.

The reactive support converts the energy of the electric current into the energy of the electromagnetic field. Like the Lancug, which has inductance L, apply a changeable voltage with frequency f, then the reactive support is more modern

The greater the reactive support, the lesser the changeable strum.

The reactive support depends on the frequency. Elements with low inductance create negligibly little resistance at low frequencies, and beyond the transition from a frequency of 50 Hertz to a frequency of 50 MHz (megahertz), the response increases a million times.

At low frequencies, it is not necessary to respect the inductance of small fragments, but at hundreds of megahertz and gigahertz it is necessary to respect the inductance of radio components. In the technology of high frequencies, there are stagnant elements without frames, like dangling pins. Natomist - contact plates, which are soldered onto a circuit board.

A lance with an inductive support, when supplying a changeable jet, produces electromagnetic coils. Another possible and reversible process: when an electromagnetic field is injected into the inductance, a changeable current is induced.

Washing machine and inductive support

Operators of automatic washing machines often complain that the wire “breaks through to the drum.” Electrical insulation of such machines, as a rule, is in good order, but all the same, it is unacceptable to reach the metal drum, with the emphasis and vivantage of speeches.

The reason is due to the induced struma. The automatic machine contains a power supply unit, in which the moderate voltage is converted to high-frequency. This high-frequency voltage is applied to all electrically conductive objects, looking at the metal drum. The inductance of the drum is not standardized, but, melodiously, it is small. The high frequency flow of the electronic circuit induces a small flow on the metal parts of the washing machine.

A similar phenomenon can be observed in daily water heaters with electronic heaters that heat tap water. If the living block of the device is located close to the water pipe, a high-frequency stream can be directed at it, and the water from the tap can be “spiked.” Unacceptable outputs can be eliminated by turning off the electrical power to the boiler.

Inductance of the human body

Our body is an electrical conductor, and all conductors, in this and other worlds, are inductive. This means that we are susceptible to the infusion of the electromagnetic field, under which our body can be induced by alternating currents.

The inductivity of the human body is significantly less. than the inductance of the antenna and the throttle, and the small electromagnetic fields have little impact on us. However, the greater the tension of vibration, and the greater the frequency of the electromagnetic field, the stronger the influx. The stronger the field in the low frequency range becomes fatally dangerous.

To protect people in workplaces associated with strong electromagnetic fields, wear special shielding clothing and shielded areas. There are areas that are closed for ventilation around heavy antennas and radars.

From time to time, information appears about the problem of troublesome growths on a mobile phone, when the hearing is pressed to the head. The phone transmits a high-frequency electromagnetic signal of low intensity, and through low intensity its influx is insignificant. However, in the event of a severe influx, viprominyuvannya can lead to bad health. Vikoristovvati Skype, installation on your computer, better.

The electric current, which passes through the circuit, creates a magnetic field around it. Magnetic flow Φ through the circuit of this conductor (called power magnetic flux) is proportional to the modulus of induction B of the magnetic field in the middle of the circuit \(\left(\Phi \sim B \right)\), and the induction of the magnetic field is proportional to the strength of the stream in the circuit \(\left(B\sim I \right)\ )).

Thus, the power magnetic flow is directly proportional to the force of the flow in the circuit \(\left(\Phi \sim I \right)\). This storage can be mathematically represented as follows:

\(\Phi = L \cdot I,\)

De L- Proportionality coefficient, which is called circuit inductance.

• Circuit inductance- a scalar physical quantity, numerically equal to the strength of the magnetic flux that penetrates the circuit, to the strength of the current in the new one:

For SI unit of inductance є henry (Gn):

1 H = 1 Wb/(1 A).

• The inductance of the circuit is 1 H, due to the constant flow of 1 A, the magnetic flux through the circuit is 1 Wb.

The inductance of the circuit depends on the size and shape of the circuit, on the magnetic power of the middle in which the circuit is located, and does not depend on the strength of the conductor. Thus, the inductance of the solenoid can be expressed using the formula

\(~L = \mu \cdot \mu_0 \cdot N^2 \cdot \dfrac(S)(l),\)

De μ - magnetic penetration of the core, μ 0 - magnetic stability, N- Number of solenoid turns, S- coil area, l- Dovzhina solenoid.

With the constant shape and size of an unbroken circuit, the magnetic flow through this circuit can change without changing the strength of the current, then.

\(\Delta \Phi =L \cdot \Delta I.\) (1)

The phenomenon of self-induction

If the circuit passes through a constant current, there is a constant magnetic field around the circuit, and the magnetic flow that runs through the circuit does not change over time.

If the flow that passes near the circuit changes over time, then the alternating magnetic flux that obviously changes, and, according to the law of electromagnetic induction, creates in the EPC contour.

• The cause of EPC induction in a circuit, which is caused by a change in the power flow in that circuit, is called a phenomenon of self-induction. Self-induction was discovered by the American physicist J. Henry in 1832.

EPC-ERS, which appears in this case, self-induction E si. EPC of self-induction is created in the circuit of self-induction streams I si.

The direct stream of self-induction is determined by Lenz's rule: the stream of self-induction is immediately straightened so that it prevents a change in the main stream. As the main stream grows, then the stream of self-induction of directness against the straightening of the main stream changes, then the direction of the main stream and the stream of self-induction are avoided.

Vikorist law of electromagnetic induction for an inductance circuit L and level (1), the expression for EPC self-induction is selected:

\(E_(si) =-\dfrac(\Delta \Phi )(\Delta t)=-L\cdot \dfrac(\Delta I)(\Delta t).\)

• EPC of self-induction is directly proportional to the speed of change in the flow rate in the circuit, taken from the prolongation sign. This formula can only be used with equal changes or changes. With increased struma (Δ I> 0), EPC is negative (E si< 0), т.е. индукционный ток направлен в противоположную сторону тока источника. При уменьшении тока (ΔI < 0), ЭДС положительная (E si >0), then. The inductive stream of straightening is the same as the stream of the dzherel.

From the omitted formula it appears that

\(L=-E_(si) \cdot \dfrac(\Delta t)(\Delta I).\)

• Inductance- This is a physical quantity, numerically equal to the EPC self-induction that occurs in the circuit when the power supply changes by 1 A in 1 s.

The phenomenon of self-induction can be detected using the simplest evidence. Small picture 1 shows a diagram of the parallel connection of two lamps. One of them is connected to the core via a resistor R, and otherwise - consistently with the cat L. When the key is closed, the first lamp burns out almost immediately, and the other - with noticeable damage. This is explained by the fact that the lancet with a lamp is on display 1 There is no inductance, there will be no self-induction in this stream, and the power of the stream in this lamp may soon reach its maximum value. In the field with a lamp 2 with increased struma in the lancus (from zero to maximum) the struma is self-induction I si which crosses the intense flow in the lamp. Baby 2 shows a diagram of how to change the struma in the lamp 2 when the lance is stuck.

When the key is opened, the lamp is strummed 2 We also extinguish completely (Fig. 3, a). If the inductance of the coil is high, then immediately after opening the key you can turn on a larger current (lamp 2 burns more strongly), and then the strum begins to change (Fig. 3, b).

The self-induction mechanism creates a spark where the lance is released. Since the lances have strong electromagnets, the spark can turn into an arc discharge and seize the electrical power. To dissolve such lances at power plants, use special chemicals.

Magnetic field energy

Energy of the magnetic field in the inductance circuit L from the force of the stream I

\(~W_m = \dfrac(L \cdot I^2)(2).\)

Fragments \(~\Phi = L \cdot I\), then the energy of the magnetic field of the stream (coil) can be recovered, knowing whether there are two quantities out of three ( Φ, L, I):

\(~W_m = \dfrac(L \cdot I^2)(2) = \dfrac(\Phi \cdot I)(2)=\dfrac(\Phi^2)(2L).\)

The energy of the magnetic field, placed in one unit of space occupied by the field, is called volumetric intensity of energy magnetic field:

\(\omega_m = \dfrac(W_m)(V).\)

*Videdennya formula

1 visnovok.

A conductive circuit with inductance is connected to the jet stream L. Let the force of the stream gradually increase from zero to a certain value in a short period of time Δt I (Δ I = I). Self-induction EPC is more modern

\(E_(si) =-L \cdot \dfrac(\Delta I)(\Delta t) = -L \cdot \dfrac(I)(\Delta t).\)

Over this period of time Δ t charge is transferred through the circuit

\(\Delta q = \left\langle I \right \rangle \cdot \Delta t,\)

where \(\left \langle I \right \rangle = \dfrac(I)(2)\) - average value of the struma force per hour Δ t at a steady state it increases from zero to I.

Stream force in a circuit with inductance L reaches its meaning not in a meeting, but over the course of a certain final period of time Δ t. In this case, the EPC is due to self-induction of E si, which overcomes the increasing strength of the struma. Well, then, under the hour of stopping the current work against EPC self-induction, then.

\(A = -E_(si) \cdot \Delta q.\)

The work is carried out by the core of the created strum in the circuit (without regulating heat losses), and means the energy of the magnetic field that is stored by the circuit and the strum. Tom

\(W_m = A = L \cdot \dfrac(I)(\Delta t) \cdot \dfrac(I)(2) \cdot \Delta t = \dfrac(L \cdot I^2)(2).\ )

2 visnovok.

Since the magnetic field is created by the flow that passes at the solenoid, then the inductance and the inductance module of the magnetic field of the coil are equal

\(~L = \mu \cdot \mu_0 \cdot \dfrac (N^2)(l) \cdot S, \,\,\, ~B = \dfrac (\mu \cdot \mu_0 \cdot N \cdot I)(l)\)

\(I = \dfrac (B \cdot l)(\mu \cdot \mu_0 \cdot N).\)

Having substituted the expressions for the formula for the energy of the magnetic field, we can eliminate

\(~W_m = \dfrac (1)(2) \cdot \mu \cdot \mu_0 \cdot \dfrac (N^2)(l) \cdot S \cdot \dfrac (B^2 \cdot l^2) ((\mu \cdot \mu_0)^2 \cdot N^2) = \dfrac (1)(2) \cdot \dfrac (B^2)(\mu \cdot \mu_0) \cdot S \cdot l. \)

Shards \(~S \cdot l = V\) - around the cat, the strength of the magnetic field energy is ancient

\(\omega_m = \dfrac (B^2)(2\mu \cdot \mu_0),\)

de U- magnetic field induction module, μ – magnetic penetration of the medium, μ 0 – magnetic constant.

Literature

1. Aksenovich L. A. Physics in secondary school: Theory. Zavdannya. Testi: Navch. a guide for installations that will ensure the removal of the zipper. seredovishch, illumination / L. A. Aksenovich, N. N. Rakina, K. S. Farino; Per ed. K. S. Farino. – Mn.: Adukatsiya i vikhovuvannya, 2004. – P. 351-355, 432-434.
2. Zhilko V.V. Physics: navch. Handbook for 11th grade. zagalnosvit. installed language Navchannya with the 12-river term navchannya (basic and advances of the river) / V.V. Zhilko, L.G. Markovich. - Mn.: Nar. Asveta, 2008. – pp. 183-188.
3. Myakishev, G.Ya. Physics: Electrodynamics. 10-11 grades : navch. for the lost science of physics/G.Ya. Myakishev, A.3. Sinyakov, V.A. Slobidsk – M.: Bustard, 2005. – P. 417-424.