Brief summary of grade 8

Heat phenomena

The body temperature depends on the speed of molecules.

Meful movement molecules called thermal motion.

Internal energy - This is the sum of the potential and kinetic energy of all molecules, of which the substance consists.

Internal energy does not dependfrom fur. Body movement or its position relative to other bodies.

With increasing T˚ increases.

Changes 2 ways:

1. By performing work;

2. By heat exchange (heat transfer)

Heat transfer:

1. Thermal conductivity - Transmission E from one part of the body to another as a result of thermal motion of molecules (TV. Body)

2. Convection- movement of the very substance in liquids and gases. (liquid and gas)

3. Radiation- emission rays (no medium is needed, perhaps in vacuo)

Quantity of heat - The energy obtained or given by the body during heat transfer.

Processes:

I. Heating or cooling (without changing the aggregate state of the substance)

m - Massa

Temperature change

c is a specific heat, numerically equal to the amount of heat that must be informed to each kg of this substance to increase its T˚ per 1 ° C.

II. Fuel combustion

m - Massa

q is the specific heat combustion of fuel - a physical value showing how the amount of heat is highlighted with complete combustion of the fuel weighing 1 kg.

3. Variousness (evaporation, boiling)

Condensation

5. Desublimation

6. Sublimation (sublimation)

III. Melting and crystallization

The melting or crystallization process is carried out on the horizontal section of the chart of AV at a constant temperature called melting temperature.(Tablekaya)

This graph is represented by an example of ice melting.

Point A - only ice

AV - ice with water

Point in - only water

Melting - Q is summed up by the system.

Crystallization - Q Distributed from the system

m - Massa

λ – specific heat meltingshows which amount of heat should be transferred to each kg of substance taken at a melting point to completely melted.

IV. Various and condensation

The process of vaporization or condensation is carried out on the horizontal section of the chart of AV at a constant temperature called boil temperature. (Tablekaya)

This schedule is represented by the example of boiling water.

Point A - only water

Plot AV - water and her couples

Point in - only couples

Vaporization - Q is summed up by the system

Condensation - Q is given away from the system

m - Massa

L - specific heat steamingshows which amount of heat must be informant to each kg of liquid taken at the boiling point to turn the liquid into steam.

Saturated steam - Couples in dynamic equilibrium with its liquid. (How many molecules goes from a liquid into pairs, as much and passes back, from steam into liquid.)

ü Absolute humidity - Density of water vapor in the air.

ü Relative humidity - The ratio of absolute moisture to the saturated pair density at the same temperature.

The dew point is the temperature at which the pairs becomes saturated.

Hygrometer and psychrometer - instruments for measuring air humidity.

Heat engineand - these are machines in which the internal energy of fuel in mechanical energy occurs.

The efficiency is the ratio of the perfect useful engine operation, to the energy obtained from the heater.

Electrical phenomena

Electrostatics - section that studies resting charges.

Electrized bodies or attract or repel.

The physical quantity characterizing the degree of electrification of the body is called an electric charge.

Methods of electrification:

1) Contact (friction)

2) Touch

3) through influence

It is conventionally believed that the glass wand, loss of silk - charging positivelyand ebonite wand, loss of wool - negative.

The same charged bodies are always repelled, differently charged bodies are attracted.

Around the charged body (or motionless charge) exists electric field. When interacting the fields arise coulomb forces.

And - charges in CL

– distance between charges

k. - coefficient

Calculation force calculation is possible for three cases:

1. The interaction of two charged areas (R - from the center to the center)

2. The interaction of the charged sphere and point charge (charged body, the sizes of which can be neglected)

3. Interaction of two point charges

Electroscope - an instrument for measuring the electrical charge.

Electricity - directional and ordered movement of charged particles. (in metals - electron movement)

All substances on the conductivity of EL. The current is divided into 3 groups:

1) Conditions(metals, solutions - in normal conditions there are sufficiently charged particles)

2) Semiconductors - Substances containing free charged particles to a lesser extent (Germany, silicon)

3) Dielectrics (Ranges) - Do not have free charged particles - rubber, ebonite, distillir. water.

Insulator - Body made of dielectric.

Electron - particle with the smallest negative charge.

Center - core (massive and positive): Protons (+) and neutrons (0)

Around the kernel - electrons (lungs and negative)

Normal condition - neutral atom - Number of protons \u003d electrons

Positive ion - atom who has lost one or more electrons

Negative ion - an atom attaching an excess electron

Conditions for the occurrence of electric current:

1) Explorer

2) the presence of an electric field

3) current source - a device in which charges are separated

4) Closed electrical chain

El. The chain consists of:

ü source current

ü consumers

ü supplying wires

ü measuring instruments

Ammeter - this is an instrument for measuring the current strength in the chain; turns on consistent!

Voltmeter - this is a device for measuring the voltage in the chain or on its site; turns on parallel!

Tok Power - The physical value determined by the amount or value of the charge flowing through the cross-section of the conductor per unit of time. Ampere

Voltage - The physical value, numerically equal to the attitude of the work that the electric field performs when the charge is moving, to the magnitude of this charge. Volt

The strength of the current in the conductor is directly proportional to the voltage at the ends of the conductor.

Resistance - The physical quantity characterizing the properties of the conductor is more or less influenced by charge.

l. – explorer length

S. - Cross-section area of \u200b\u200bthe conductor

- Specific resistance (depends on the material of the conductor) is given in the tables!

Ohm's lawfor chain section:

R. - constant for this conductor \u003d\u003e does not depend on I and U.

Reostat - the device for regulating the current in the chain.

Serial connection of conductors	Parallel connection of conductors

Operation of electric current

The power of the electric current is a physical value that characterizes the speed of the work performed.

Or - in practice

Joule-Lenza law: (Heating conductor)

Short closure - compounding the ends of the circuit area by the conductor, the resistance of which is very little compared to the resistance of the circuit site.

Electromagnetic phenomena

The magnetic field exists around any conductor with a current, i.e. Around moving charges.

Moving charges (charged particles) - source of magnetic field

Picture M.P. You can use magnetic (power) lines. Magnetic lines are closed by themselves (do not have the beginning and end) or go out of infinity in infinity.

Magnetic field of conductor with current:

To determine the direction of lines m. Fields use 2 rules:

1) Brascover rule

If the progressive movement of the reel coincides with the direction of current in the conductor, the rotational movement of the bouwn handle coincides with the direction of the magnetic field lines.

2) Right Hand Clamp Rule

If the thumb is the right hand to send in the direction of the current, then 4 fingers will show the direction of the magnetic field lines.

Magnetic field coil with current:

Inside the coil line parallel and do not intersect. Always go from the north to south. The current direction indicates the North Pole.

Determine the direction of the magnetic field lines inside the coil can be using rules of right hand:

If 4 fingers right hand are sent in the direction of the current in the coil twists (claw the current coil), then the retired thumb show the direction of the magnetic field lines inside the coil.

The coil with the core inside is called - electromagnet.

Permanent magnets:

The magnetic field of the permanent magnet is due to the annular currents of the ampere. (rotation of electrons in atoms of substance in one direction)

The magnetic poles of the Earth do not coincide with its geographic poles.

Northern Magnetic Pole - N (South Geogr. Pole)

Southern Magnetic Pole - S (North Geogr. Pole)

Power characteristic of the magnetic field -

vector magnetic induction B.

The vector is a tangent to the magnetic field lines and is directed as well as the magnetic field line.

Magnetic field effect on bodies placed in it:

Explorer with current	Charged particle
Rule of left hand
Ampere power	Lorentz power
I.- Current power in the conductor B.- magnetic induction l - Explorer length, which is located in M.P.	q -called particles (module) V -particle speed B -magnetic induction
If the left hands are so that the lines of the magnetic field are entering the palm, and 4 fingers pointed to the current direction in the conductor, then repayed by 90˚ thumb showing the direction of the ampere force.	If the left hand is to be positioned so that the magnetic field lines are entering the palm, and 4 fingers pointed to the direction of movement (speed) of a positively charged particle, then repayed by 90˚ thumb showing the direction of the Lorentz force. (For a negative particle - 4 fingers against the direction of the particle speed)

Light phenomena

Optics are a section of physics studying light phenomena and patterns.

Light is an electromagnetic wave.

The point source of light is the dimensions of the luminous body much less than the distance on which we estimate its action.

Light beam - Line, along which the energy from the light source is spread.

Shadow - The area of \u200b\u200bspace in which the light is falling from the source.

Penumbra - It gets light from the source.

Light energy propagating between two rays is called light beam.

Laws of Geo. Optics:

1) Law of reflection of light

1. The ray falling, the beam reflected and perpendicular, restored to the fall point, lie in the same plane.

2. The angle of the fall is equal to the angle of reflection.

Angle of incidence - The angle between the falling beam and the perpendicular to the surface restored at the fall point of the beam to the surface.

The angle of reflection - The angle between the reflected ray and perpendicular to the surface restored at the fall point of the beam on the surface.

Flat mirror:

The image in a flat mirror is behind the mirror on a straight line, perpendicular surface of the mirror, and the distance from the mirror to the image e is equal to the distance from the object to the mirror of the JSC.

2) Law of refraction of light

The optical density of the medium is characterized by a different speed of light propagation.

When moving from one medium to another, the beam changes its direction on the border of these environments - refractate.

1. The ray falling, refracted and perpendicular, restored to the fall point to the border of two media, lie in the same plane.

2. The ratio of the sine angle of the fall to the sinus of the refractive angle, there is a permanent value for the data of two environments and is called the refractive index of the second medium relative to the first.

If the light comes from the medium is optically less dense into a more dense medium, the refractive angle is always less than an angle of falling.

The refracted beam in this case "presses" to the perpendicular.

If the light goes out of the environment is optically more dense into a less dense medium, the refractive angle is always larger than the angle of the fall.

The refracted beam in this case is "pressed" to the interface interface.

Ray, directional perpendicular to the border of the section two media passes without refraction.

Lens is a transparent body bounded by two spherical surfaces.

Types of lenses:

Lenses (optical properties)

Optical strength lenses:

An image of any point will be the point. Image of arrows - arrow.

Construction image Any point source (point of item) in the lens occurs on two rays.

1) ray going through the center of lenses – not refracted

2) ray going parallel to the main optical axisafter lenses refracted in t. Focus lenses

At the intersection of these two rays there is a point that is image of the source.

An image of the subject is built in the same way.

Formula of fine lenses:

The connection of the magnetic field with the current led to numerous attempts to initiate a current in the circuit using a magnetic field. If a magnetic field occurs around conductors with currents, then the reverse phenomenon should exist - the occurrence of an electric current in a closed conductor under the action of a magnetic field. This task was brilliantly resolved in 1831 by the English physicist Faraday, which opened the phenomenon of electromagnetic induction - the connection between electrical and magnetic phenomena was proved, which served to develop an electromagnetic field theory.

1. Electromagnetic induction.The phenomenon of electromagnetic induction is that with any change in the magnetic flux that penetrates the closed circuit of the conductor, an electromotive force (ED) induction occurs in the conductor, causing the appearance of an electric current, the cat is called. induction. E.D.S. Induction occurs also in the open conductor when it moves in a magnetic field, in which the conductor crosses the magnetic field line.

Experience 1.: If a solenoid is closed to a galvanometer to moving or put forward a permanent magnet, then a deviation of the galvanometer arrow (induction current) is observed at the moments of its thirty or nomination); Directions of the deviations of the arrow when moving and nominating the magnet are opposite. The deviation of the arrow of the galvanometer is the greater the greater the magnet speed relative to the coil.

Experience 2:current strength in contour 1 can be changed using a row. This current creates a magnetic field, piercing circuit 2, if you increase the current, the flow of magnetic induction through the circuit 2 will grow. This will lead to the appearance in the circuit 2 of the induction current registered by the galvanometer. Electromagnetic induction can be called:

1. Reducing the current, which causes decrease in the magnetic flux through the second circuit and will lead to the appearance of induction current of the other direction in it than in the first case.

2. Induction current can also be caused by approaching circuit 2 to contour 1 or removing the second contour from the first.

3. Not moving circuit 2 progressively, but turning it so that the angle between the normal to the contour and the direction of the field changes.

The experimental way was found that the induction current value (eD) does not depend on the method of changing the flow of magnetic induction, but is determined only by the speed of its change. those. meaning. This law is universal. (1821)

Professor of the St. Petersburg University of Lenz investigated the relationship between the direction of the induction current and the choracter of the magnetic flux caused it: the Lenza rule: induced in the circuit E.D.S. Causes a current of such a direction that the magnetic field of this current prevents the change in the magnetic flux.

For example, when the circuit is approached 2 to contour 1, the current occurs, the magnetic moment of which is directed opposite to the current field (the angle between vectors and is equal). Consequently, the strength that repelled it from the circuit will act on the circuit 2, when the circuit is removed from contour 1, the current occurs, the moment is used in the direction of the current field, so the force acting on the circuit 2 is directed to the contour 1.

Lenz received this rule from experience, analyzing numerous experiments. In fact, the action of this rule is much wider - it expresses the general principle according to which any system seeks to maintain a steady state of equilibrium and counteracts all changes in this state.

The formula that combines the Faraday law and the Lenza Yavl rule. mathematical expression of the basic law of electromagnetic induction.

The main law of electromagnetic induction(faraday Law - Maxwell). The electromotive induction force arising in a closed circuit is proportional to the rate of change of magnetic flux with time: where the number of turns of the circuit, streaming, if all the coil spikes are permeated with the same stream, then .

Note 1. Minus sign reflect lenza rule.In most cases, with numeric calculations, this sign can be omitted.

Note 2.For a closed contour.

E.D.S. expressed in volta..

To prove the Faraday Law, we use the law of conservation of energy. Consider a closed circuit in which one of the conductors can move. Position the contour into a homogeneous field, perpendicular to the drawing plane and sent for the drawing. Let the conductor move with speed. The force acting on the moving conductor. Work that is produced on the segment :. The source energy is spent on heat and work :. On the other hand, we get. The value plays the role of EDs, because It leads to the appearance in the closed circuit of the electric current. Consequently, this value is E.D.S. electromagnetic induction.

Obviously, the magnetic stream is only in cases where the conductor crossingmagnetic induction lines of the field, so they call the intersection rate by the conductor of magnetic induction lines.

For example, in the case of a rectilinear conductor, a cat. Moves in a homogeneous magnetic field perpendicular to the magnetic induction lines, E.D.S. Induction in the explorer, where the angle between the conductor and the direction of its speed.

The difference in potentials at the ends of the conductor will find from the generalized law of Ohm. Because There is no electric current in the conductor, then.

Comment. In the phenomena of electromagnetic induction, the magnetic flux through the circuit may vary both when the contour or its individual sections is moved and when the magnetic field is changed, the Faraday law is used to determine the e.D. induction.

When conducting conductors in a magnetic field, this law is applicable only in cases where the circuit under consideration passes through some and the same points moving conductor. Otherwise, E.D.S. Inductions are found by exploring Lorentz's forces acting on free charges in a moving conductor, i.e., acting in the circuit E.D.S. It is measured by the work of third-party forces when moving along a closed chain of a single positive charge, where the moved charge.

Example. A rectangular frame is located in a homogeneous magnetic field with an induction of 0.1to, the movable side of which is 0.1 m long moves with a speed perpendicular to the field induction lines. Determine EDs Induction arising in the contour.

Decision: We will solve the task in two ways by applying the Faraday law or considering the forces acting on free electrons in the moving wire (Lorentz's forces).

1. When driving, the framework of the frame increases, the magnetic flux increases, i.e. By the law of Faraday, E.D.S. induction. . The sign "-" shows that E.D. Induction acts in the circuit in such a direction in which the rule of the right screw to the contour is opposite to the rule of the right screw (directed to the observer). Those. E.D.S. Induction and induction current are directed in the circuit counterclockwise.

When solving the problem in both cases, inaccuracy is made: the magnetic field created by induction current is not taken into account. Both considered methods give the correct answer under the condition that there is a sufficiently large chain resistance.

Induction current force in a closed conductive contour with resistance :. It is considered positive if the magnetic moment of the corresponding induction current in the circuit forms a sharp angle with the magnetic induction lines of that field that brings this current.

The nature of third-party forces leading to the appearance of EDs Electromagnetic induction: Lorentz power, which acts on the charge moving in a magnetic field.

It is possible to consider a change in the magnetic flux in a fixed circuit, for example, reduce the magnitude of the magnetic induction. In this case, Lorentz's power is absent (there is no ordered movement of electric charges), but E.D.S. Arises I.

There is a special type of interaction between moving electrical charges: for example, two parallel equally targeted current are attracted, and two oppositely directed - repel. The form of matter through which the moving charges interact is called the magnetic field. The magnetic field is formed around any moving charge or conductor with a current and quantitatively characterized by the field strength - vector value, the numerical value of which binds to the form of the conductor and the power of the current. The direction of the field strength vector corresponds to the direction of the north pole of the magnetic arrow placed at this field. The magnetic field is conventionally depicted by power lines - imaginary curves, constructed so that tangents to them at any point indicate the direction of the field strength vector at the appropriate point.

For practical use, the magnetic field is formed with a coil, a streamlined current and having an iron core, which significantly enhances the field. In accordance with the nature of the current, the magnetic field may be permanent or variable. Permanent electromagnet is used, for example, to remove iron fragments from the eye (see eye magnets).

The experiments found that the magnetic field, both permanent and variable, acts on biochemical processes, and also has a certain influence and on the whole organism. With therapeutic goal, magnetic nape is not yet widely applied.

If the conductor or contour is under the action of a magnetic field varying on tension or direction, then the electromotive force arises in them, and the current is formed in the closed circuit. This phenomenon is called electromagnetic induction, and the current current is induction.

The electromotive force (EMF) of the induction also occurs in conductors with a current when changing the value or direction of current, since the magnetic field formed by this current is changed according to tension or direction. This phenomenon is called self-induction. The electromotive power of self-induction in turn affects the current flowing in the conductor, which should be taken into account accordingly. Self-induction is of great importance in alternating current circuits.

Electromagnetic induction occurs also in a continuous mass of the conductor, for example, in the mass of the electrolyte solution, placed in an appropriately changing magnetic field. The induction current in this case is represented in the form of circular currents closed in the mass of the conductor in the planes perpendicular to the field lines of the field. These currents are called vortex (Toki Foucault).

Organization of research activities of students in studying the topic: "Electromagnetic phenomena" in physics in the eighth grade of the main school in the light of the requirements of the GEF to the results of the development of the OOP

Fast accumulation of knowledge purchased

With too small independent participation, not very fruitful.

The scholarship can also give birth to leaves, not giving fruits.

Lichtenberg

The FGE of the General General Education is approved by the Order of the Ministry of Education and Science of the Russian Federation of December 17, 2010 No. 1897.

The fundamental difference between the second-generation GEF is a result orientation, which involves the development of the personality on the basis of the development of universal ways of activity.

Requirements for the results of the development of the main educational program (OOP)

(Personal, MetaPered, Subsection)

Personal - education of civil identity, readiness for self-education, the formation of a holistic worldview, communicative competence, tolerance, mastering social norms, rules of safe behavior, etc.

• MetaPered - determine the purpose of learning, plan ways to achieve them, evaluate the correctness of the implementation of the learning task, to own the foundations of self-control, semantic reading, ICT competence, etc.
• Subjects - Objective results on subject areas and subjects (experience specific for this subject area, a system of fundamental elements of scientific knowledge)

Although the mandatory introduction of GEF for the basic school has not yet come, it is necessary to rebuild its work today in such a way as to create conditions for the formation of students:

• Universal academic actions
• ICT competence
• Fundamentals of educational and project activities
• Basics of semantic reading and working with text

Universal training actions are the system of actions of the student, ensuring the ability to independently assimilate new knowledge and skills, including the organization of educational activities.

The competence approach of the FGOS focuses on the activity of education. In this case, the main content of training is actions, operationscorrelated not so much with the object of the application effort, as with the problem to be resolved. In the curriculum, the activity of education is reflected in the accent on ways of activity, skills and skillsnecessary to form on experience experiencewhich should be accumulated and comprehended by students and on training achievementswho students must demonstrate.

The implementation of the competence approach is impossible without receiving deep knowledge, since the most important sign of the competence approach is the ability of a learner to self-study in the future. The competence approach does not deny, but changes the role of knowledge. Knowledge fully obey the skills. Only the knowledge that is necessary for the formation of skills is included in the learning content. All other knowledge is considered as reference, they are stored in reference books, encyclopedias, internet, etc., and not in the heads of students. At the same time, the student must, if necessary, be able to quickly and accidentally use all these sources of information to resolve certain problems.

Thus, the competence standard is the standard of education results.

Competence is a person's willingness to mobilize knowledge, skills and external resources for effective activities in a specific life situation.

I propose as a specific example an attempt to implement a competence approach in training, i.e. The development of students in educational and research activities on the basis of a real subject experiment, the organization of educational and research activities in studying the topic: "Electromagnetic phenomena" in physics in the eighth grade of the main school. The organization of this educational and research activity of students was supposed to take into account the following principles:

• Creating internal motivation to the process of exercise based on the initiation of interest in the subject studied
• — Activity approach based on the activation of individual cognitive independence
• — Problem learning
• Principle of success of learning
• The ability to determine the volume of content and the level of complexity of the substantive material themselves

The study of this topic in the eighth grade of the main school is given seven hours. There is a demonstration and frontal experiments; Performing one laboratory work: "Build an electromagnet and testing of its action."

Material "Electromagnetic phenomena", in my opinion, makes it possible not to simply carry out various experiences, but to organize student research activities based on the use of experimental tasks on all lessons on this topic.

The organization of such activities is a rather laborious process, but far from vain. After all, it is known that the skillful conduct of the experiment is the top of studying physical phenomena, as it requires deep theoretical knowledge, the skills of the correct handling of devices, the ability to build graphs and competent calculations, the ability to evaluate the error of experience, the ability to analyze and draw conclusions.

You can learn everything this can only when you are directly involved in practical activities. Therefore, the more often the students will refer to experimental tasks, the higher the quality of their knowledge, as the acquisition for research activities, the ability to make something with their own hands develops to the same interest in the subject and helps to give it better. Thus, the lessons of physics creates a real possibility of forming universal skills and skills that students can apply on other subjects and in extracurricular, life situations.

Experimental tasks offered when studying this topic in the basic eighth grade are not difficult. They are not based on the establishment of quantitative patterns and require only a qualitative explanation. But this does not diminish their advantages. Performing such tasks to a greater extent requires students to show independence, develops the ability to analyze their work and draw conclusions that so far for eight-graders presents a certain difficulty. And, of course, the implementation of such tasks is developing the skill of work with devices and maintains the interest of students to study electromagnetic phenomena. The proposed experimental tasks are not new, they are well known. But at the same time, some novelty makes them the nature of their use. Also, from students, in addition to performing a direct experimental task, an independent theoretical explanation based on the study of the textbook text. It is proposed to consider and submit an additional material on this topic from other sources. At each lesson, students have the opportunity to advertise acquired knowledge. The development of communicative abilities contributes to the work of students in a pair and group. Of course, the successful study of this topic through educational and research activities should be preceded by a systematic appeal to the implementation of various class and home experimental tasks.

Purchant distribution of the topic of the topic "Electromagnetic phenomena"

1. Permanent magnet and conductor with current.

2. Magnetic field on paper.

3. Comparison of the magnetic field of the solenoid and permanent magnet.

4. omnipresent electromagnets.

5. Explorer with current in a magnetic field.

6. Coil with current in a magnetic field.

7. Electromagnetic world.

Experimental and methodological support for the topic.

1. Laboratory equipment: Permanent magnets, compass, small metal bodies, current source, retail, ammeter, connecting wires, key, compass, iron sawdust, tight sheet of paper, wire coil, solenoid, metal core and clip, dynamometer, electric motor model.

2. Distribution material (experimental studies)

3. Computer support for lessons. Ready products are used: "Educational complex" Preparation for EGE 10-11 class "," Physics in pictures ".

UMC student

• A.V. Pryony. Physics 8. Drof. M. 2002.
• G.N. Stepanova, A.P. Stepanov. Collection of questions and tasks in physics. Basic school. "Valery SPD" SPb. 2001.

The content of lessons

Lesson number 1

Permanent magnet and conductor with current.

The purpose of the lesson.

Enter the concept of a magnetic field.

Tasks lesson:

• make sure that the magnetic field is formed around a permanent magnet and conductor with a current;
• find out whether it is possible to detect a magnetic field with the help of senses;
• does the magnetic field refer to whether it is possible to strengthen or weaken its action.

During the classes.

Setting the purpose of the lesson.

Electrical phenomena are already considered in detail. We proceed to the study of magnetic phenomena and we will try to make sure that these phenomena are interconnected and that the new topic does not accidentally be called "electromagnetic phenomena". As this topic studies, we will conduct a research diary. We split it in half. In one half, the results of the experiments will be presented, in the other - their theoretical explanations. In the last lesson will conduct a diary competition.

You have repeatedly collected the electric chains and got acquainted with the peculiarities of the electric current in them, and more than once in their lives used permanent magnets. Let's find out if there is something in common with a permanent magnet and conductor with a current?

What do you know from your life experience about the properties of permanent magnets? We clarify your knowledge with the help of experience.

Experimental study №1

Permanent magnet

Purpose of the study: Determine what properties has a permanent magnet.

Equipment: Permanent magnet, compass, small metal bodies.

Structure of research.

1. Apply the permanent magnet in turn to the pencil, rubber band and to different metal bodies.

Observe what will happen.

2. Get the highest possible attraction of bodies with a magnet.

Pay attention to how these bodies attracted to which parts of the magnet.

3. Apply the magnetic arrow from different sides to the magnet.

Just over the behavior of the arrow of the compass.

4. According to your observations, we formulate the basic properties of a permanent magnet.

Explorer with current

Purpose of the study: Find out that it combines a permanent magnet and a conductor with a current.

Structure of research.

1. With the help of the senses, explore the space around a permanent magnet and around some body (line, pencil).

2. Explore the space around a permanent magnet and around some body (ruler, pencil) with a compass.

Take a conclusion about the results of your experience.

3. Design the circuit circuit consisting of a current source, a row, ammeter, key and connecting wires, connecting all the elements sequentially:

• Place any connecting wire above the compass arrow parallel to its arrow at a short distance, not closer chains (the compass lies on the table). Does the compass arrow deflect?
• Close the chain, just do what will happen to the compass arrow.
• Remove the compass, open the chain. Try to determine with the help of senses, whether something changes when the chain is closed.

4. Business output according to the results of the study.

(Permanent magnet and conductor with current interact with a magnetic arrow)

Working with a textbook. (Computer model of Ersteda's experience)

• Who and when first made experience with a conductor with a current and magnetic arrow?
• What happened in our study on a magnetic arrow, rejecting it?
• As you can now answer the question: What unites the permanent magnet and the conductor with the current?

Is it possible to detect a magnetic field using the sense organs?

And how can I find it?

The outcome of the lesson.

The invisibility object is detected. What? Where? With using what? What happened about him?

Homework

Using the material 56 and 59 of the textbook paragraphs, let theoretical explanation of your experiments.

Lesson number 2.

Magnetic field on paper.

The purpose of the lesson .

Machine with a graphical way of an image of magnetic fields.

Tasks lesson.

• Find out whether the magnetic field does the direction and whether it is possible to strengthen or weaken its action.
• Enter the concept of magnetic lines.
• Find out what role Iron sawdust play
• Consider the picture of the magnetic lines of a permanent magnet and conductor with a current.

During the classes

Setting the purpose of the lesson.

Find out about the existence of a magnetic field. It turns out that physicists have long learned to depict an invisibility object on paper using certain rules. Let's find out what served as the basis for creating these rules and how to portray magnetic fields on paper. To do this, again, we will conduct experimental studies, but first remember that we already know about the magnetic field, and we define what else to find out.

Recovering diaries. Comparison and clarification of conclusions. Amendments. Discussion of the hypothesis of the ampere. The main conclusion: the magnetic field is formed around moving electrical charges.

So, is it possible to detect a magnetic field using the sense organs? What other object cannot be detected using the senses? What is his source?

Let's return to the field magnetic. How can it be detected? Are these knowledge enough to portray the magnetic field on paper? What you need to know about him yet?

Is it possible to weaken or strengthen its action?

Does it have a direction?

To answer these questions, we will conduct the following study.

Experimental study number 3.

A magnetic field

Purpose of the study: Find out whether the magnetic field has a direction and is it possible to strengthen or weaken its action.

Equipment: Permanent Magnet, Current source, Reostat, Ammeter, Connecting Wires, Key, Compass.

Structure of research

1. Do compass from different sides to a permanent magnet.

Is the compass arrow equally behave?

2. Install the compass arrow near the edges of the magnet and in the middle of it. Watch the arrow behavior in each case.

3. To select the distance on which the permanent magnet does not act on the arrow. Add another magnet to it. Watch what happens.

4. Made several times Ersted's experience, changing the direction and current strength in the conductor. Watch for the behavior of the compass arrow in each case.

5. Record the findings on the results of the study.

So, the magnetic field can act more or weaker, and in different directions. Consequently, it may be weak or strong and has a direction. And all this needs to be taken into account when it is depicting it on paper.

Since the magnetic arrow in a magnetic field is oriented in a certain way, it would be logical to connect the direction of the magnetic field with a certain direction of the magnetic arrow.

Physics acted and acted, and for the direction of the magnetic field they accepted the direction coinciding with the direction, which indicates the north pole of the magnetic arrow. Also, they agreed to portray the magnetic field with the help of lines, along which the axis of small magnetic arrows are located. Let's call them magnetic lines. The direction of magnetic lines at each point of the field coincides with the direction, which indicates the north pole of the magnetic arrow. Ordinary iron solids helped determine the nature of the location of magnetic lines. Why? Let's find out!

Experimental study number 4.

Iron Owls

Purpose of the study:find out what role Iron sawdust playwhen studying the magnetic field.

Equipment: Permanent magnet, iron sawdust, tight sheet of paper.

Structure of research

1. Put the paper sheet on a pencil. Pour iron sawdust on paper. Gently knock on the sheet of paper. Observe what will happen.
2. Repeat your actions by taking a permanent magnet instead of a pencil.
3. Gently turn the magnet under a sheet of paper, not a touch of sawdust.
4. Compare the luggage of iron sawdust.
5. Take a conclusion about the behavior of iron sawdust in the magnetic field.
   Working with a textbook.
   What is general in the location of the magnetic lines of a permanent magnet and conductor with a current?
   How can I change the direction of magnetic conductor lines with current and constant magnets?
   Demonstration and discussion of a video trip: Magnetic lines of direct conductor with current.
   Continuation of research number 4.
6. Get a picture of magnetic lines between the eponymous poles of magnets.
7. Direct the magnets with multi-poles to each other.
8. Observe what happens.
9. Explain your observations.

The outcome of the lesson.

With what makes graphically magnetic fields depict? The rules on which paintings of various magnetic fields are obtained are conditional or based on experience (demonstration of computer models)?

Homework

• Using the material 56 and 57 of the textbook paragraphs, make the necessary additions of the lesson in your opinion.
• From the Collection of Tasks, comply with №1849 and No. 1880.

Lesson number 3.

Comparison of the magnetic field of the solenoid and permanent magnet.

The purpose of the lesson:

explore and compare the magnetic field of the coil with current

with a magnetic field of a permanent magnet.

Tasks lesson:

to find out under what conditions around the wire coil is formed a magnetic field;

from which the picture of the magnetic field of the solenoid depends.

During the classes.

Magnetic fields can be depicted graphically. How?

Let us now try to predict its properties at the famous picture of the magnetic field. I will verify your own conclusions. To do this, compare the pattern of the magnetic field of the coil with current (solenoid) with the pattern of the magnetic field of the strip magnet.

Demonstration of a computer model (disc: "Physics in pictures"):

an image of magnetic fields of permanent magnet and solenoid.

Analysis of the model.

Comparing the thickness of magnetic lines in both bodies, you can allocate ... (poles)

And at a permanent magnet, and the solenoid has another area where the magnetic field is ... (uniform)

So, in this case, the pattern of magnetic fields of the bandage magnet and coils with a current ... (same). Will their properties be the same?

Is there always the pictures of these fields similar?

We will conduct an experimental study.

Experimental study №5

Solenoid

Purpose of the study:

• check whether the properties of magnetic fields of the bandage magnet and solenoid will be the same;
• to find out how to change the properties of the magnetic field of the solenoid.

Equipment: current source, wire coil, solenoid, retain, ammeter, connecting wires, key, compass, metal core.

Structure of research

1. Speed \u200b\u200bwith wire turns:

• With the help of the existing equipment, create a magnetic field from a wire turnout (use all devices that can be turned on in an electrical circuit).
• Make sure it is. Determine its direction.
• Determine if there is a pole at the turn with a current.
• Take the conclusion about the character of the magnetic field of the turn with the current.
• Change the current direction in the twist.
• Find out if his magnetic field changed?

2. Solenoid spent:

• Repeat the experiments by taking the coil instead of the turn (solenoid).

• Did the character of the magnetic field changed?
• Using the row, reinforce the solenoid magnetic field.
• Make sure it has become stronger.
• Insert the metal core in the solenoid.
• Determine how at the same time the character of the magnetic field of the solenoid has changed.

3.Dell a conclusion on the results of the study in accordance with its goal.

The outcome of the lesson.

Return to a computer model.

So is it always the pattern of magnetic fields of a permanent magnet and solenoid will be the same?

Explanation of solenoid magnetic lines varying on the slide of paintings.

Can we also easily change the picture of the magnetic lines of the bandage magnet?

Permanent magnets can also be called natural magnets. And solenoid? (artificial magnet). A magnet has been created using an electric current. Therefore, such magnets are called electromagnets.

Homework:

• Find out who and when invented the first electromagnet, where electromagnets are used today, finding information in a textbook or other sources (Paragraph No. 58).
• Also offer your ways to use electromagnets.
• From the Collection of Tasks, execute № 1895.

Lesson number 4.

Omnipresent electromagnets.

The purpose of the lesson: consider the use of electromagnets.

Tasks lesson:

• find out how can be managed by electromagnets
• disassemble specific cases of the use of electromagnets
• determine the benefits of electromagnets before permanent magnets

During the classes

1. Suit of the purpose of the lesson.

Performing homework, probably made sure that the electromagnets found very wide use. Let's find out why it became possible, and on specific examples we define the benefits of electromagnets.

Let's start by parsing a homework. What was suggested to explore in this task? What you can offer research methods. Let's now conduct a similar study.

Experimental study №6

Electromagnets

Purpose of the study: To find out how the power of the interaction of an electromagnet with a metal clip from the current strength in its winding depends.

Equipment: current source, solenoid, retail, ammeter, connecting wires, key, metal core and clip, dynamometer.

Structure of research

1. Save the study plan.

2. Entertain it.

3.Dell a conclusion based on the results of your study in accordance with its goal (an analysis of the graphical representation of the results of the study is assumed).

Work in groups.

1. Report the results of your research.
2. Give the examples of the use of electromagnets known to you.
3. Give your examples of the use of electromagnets.
4. Explain the actions of the electromagnets discussed in the task of the textbook number 9. (Accompanied by a demonstration or video.)
5. Let us explain the possibility of widespread electromagnets.

The outcome of the lesson.

The lesson was called: "omnipresent electromagnets". Did he justify his name? Argument your answer. Write your arguments briefly.

Homework.

• Make sure that you are all right in your diary.
• Perform an exercise number 28 of the textbook.
• From the collection of tasks, comply with No. 1905 and No. 1907.

Lesson number 5.

Conductor with current in a magnetic field.

The purpose of the lesson: consider the action of the magnetic field to the conductor with the current.

Tasks lesson:

• Find out what will happen to a conductor with a current if you make it in a magnetic field.
• Determine from which the module and the direction of force of the ampere depends.
• Find out how you can get to turn the turn with a current in a magnetic field.

During the classes

Collapse and adjust homework.

Placeing diaries and tasks performed.

Setting the purpose of the lesson.

The use of a magnetic field is not limited to the operation of electromagnets. All you know about the use of electric motors. It's time to figure out how they work. To do this, find out how the conductor is behaved with a current in a magnetic field.

We will conduct experiences.

Experimental study number 7.

Conductor with current in a magnetic field

Purpose of the study: Find out what happens to the conductor with a current in a magnetic field.

Equipment: current source, wire coil, retain, ammeter, connecting wires, key, constant arcuate magnet.

Structure of research

1. Design the circuit of an electrical circuit consisting of a current source, a row, ammeter, a wire cooler, a key and connecting wires, connecting all the elements sequentially.

• Collect the electrical chain according to this scheme.
• Jump the turn on a permanent magnet.
• Close the chain. Jump out that it will happen with a turn.
• Repeat experiments by changing the position of the magnet.
• Repeat the experiments using two magnets folded together with the poles of the same name.
• Jump what changes will occur.
• Repeat the experiments by changing the direction in turn and current strength in the twist.
• Take the conclusion about what and how it happens with a turn with a current in a magnetic field.
• Try to force the turn with the current to rotate in a magnetic field.
• Explain how you achieved it.
• Tell us about your observations and conclusions (showing demonstrations with a direct conductor with a current in a magnetic field).

The outcome of the lesson.

• So, the magnetic field can be detected not only in its action on a magnetic arrow, but also by action on ....? The module and the direction of force acting on the conductor with the current in the magnetic field depends on ...? The action of the magnetic field on the conductor placed in it is used in electrical engines. The next lesson will get acquainted with their device.

Homework.

• Using the article 61 of the paragraph, explain the course of the experiments shown in Figures 113 and 114 of the textbook;
• give examples of the use of electrical engines;
• find out who and when invented the first electric motor suitable for practical application.
• Do not forget about your diaries!

Lesson number 6.

Current coil in magnetic field

The purpose of the lesson: consider the device and the principle of operation of electrical engines and electrical measuring instruments.

Tasks lesson:

• To find out how practically you can rotate the conductor with a current in a magnetic field.
• Consider the device of the technical electric motor.
• Determine the advantages of electrical engines in front of thermal.
• Consider the device of electrical instruments.

During the classes

Collapse, adjustment of homework and setting the purpose of the lesson.

It was found out that the magnetic field acts onto the conductor placed in it. And as already convinced, it may even turn it!

Give examples of the use of electrical engines. Remember what makes their action. What do you think the nature of the motion of the conductor with the current is used in electrical engines?

Let's find out how can I get the conductor with a current in a magnetic field? And get acquainted finally with the device of technical electric motors and other devices that use rotation

conductor with current in a magnetic field.

Recall why the turn with the current rotated in a magnetic field. What you need to take, so that he does not just turn, and also rotate?

Experimental study number 8.

Purpose of the study: Find out how technically the rotation of the frame with the current in the magnetic field is performed.

Equipment: Model of an electric motor.

1. Word the conditions under which the frame with the current will rotate in the magnetic field.

2. Consider the electric motor model (video segment).

3. Name the devices allowing the frame with the current to rotate in a magnetic field and explain how they act.

Working with a textbook.

1. Fill the table.

Main parts of the electric motor

Purpose

Device

2. Determine the advantages of electric motors in front of thermal.

3. Complete the Tutorial # 11.

The outcome of the lesson.

Placement of completed tables. Debris proposed tasks. Make sure that the rotation of the conductor with the current in the magnetic field is widely used.

Determine what is general and what the difference in the operation of electric engines and electrical measuring instruments.

Homework.

• From the task collection, execute №1920 and №1928.

• Prepare research diaries to check.
• Consider the final collection of arguments acting as evidence that the topic studied does not accidentally be called: "electromagnetic phenomena".
• With the help of a textbook (paragraph number 60) and additional sources, collect information about the magnetic field of the Earth.

Lesson number 7.

Electromagnetic world.

The purpose of the lesson: to summarize and systematize the material of the topic: "Electromagnetic phenomena"

Tasks lesson:

• Organize analytical activities of students.
• Check the degree of assimilation of the topic of theme material.

During the classes

The lesson is carried out in the form of competition between students, broken into three large groups, each of which is divided in turn on experimenters, theorists and experts.

· Perform tasks.

1. Experiments are prepared using the proposed equipment a demonstration of electromagnetic phenomena.

2. Theoretics are preparing for the statement of arguments on the material of homework.

3. Experts evaluate the research diaries of the team members and choose the best of them.

· Placement of completed tasks.

1. Commands in turn represent their arguments, including demonstrating experienced evidence.

2. The exhibition of the best diaries is expensive.

· Check jobs.

1. Related "Pyramid".

2. Testing.

"Pyramid"

It is necessary to guess the words, explaining their value using only the topic of the topic: "Electromagnetic phenomena".

arrow magnet line

Land of the coil field

Ersted sawdust core

Electromagnetic direction of iron

Compass Solenoid Gustot

Nickel Pole Storma

Test

1. Magnetic arrow always turns:

A) in the magnetic field of the Earth;

B) near a permanent magnet;

C) near the conductor with current

D) near the ebonite stick.

2. It happens because it is formed around these bodies:

A) gravitational field;

B) magnetic field;

C) electric field;

D) biofield.

Z. Since the magnetic field is formed around charged particles, if they are:

A) exist;

B) rest;

C) face;

D) move.

4. To change the poles from the solenoid you need:

A) change the direction of magnetic lines in it;

B) increase current strength in the chain;

C) change the polarity of the current source connection;

D) change the direction of winding the solenoid wire.

5. To enhance the solenoid magnetic field:

A) remove the core from it

B) reduce the overall resistance of the chain;

C) increase the number of turns;

D) Perform a winding from a thinner wire.

6. Electromagnet can be applied to

A) closer the chain at the right moment;

B) move the heavy metal cargo;

C) extract the smallest metal bodies from the eye;

D) Make a secret valve on the door.

Check test

1. Magnetic field in vacuo and its characteristics: vector magnetic induction and magnetic field strength vector. Magnetic field and magnetic moment of circular current.

Permanent magnets were known 2 thousand years ago, but only in 1820. H. Ersted (Danish physicist) found that a magnetic field is created around the conductor with a current, which affects the magnetic arrow. In the future, it was found that the magnetic field is created by any moving bodies or charges. The magnetic field, as well as electrical, is one of the types of matter. The magnetic field has energy. Through the magnetic field, the interaction between electric currents moving charges. Experience shows that the nature of the impact of the magnetic field on the current is varied depending on the shape of the conductor, through which the current flows, from the location of the conductor and on the current direction. Therefore, in order to characterize the magnetic field, it is necessary to consider its action on a certain current.

For the study of the electric field used a trial point charge. Similarly, for the study of the magnetic field, a frame with a current is used, the dimensions of which are small compared with the distance to the currents forming the magnetic field. The orientation of the contour (frame frame) in space is characterized by the direction of normal to the contour. The positive direction of the normal is determined by the rule of right hand: the four fingers of the right hand are located in the direction of current in the frame, reverting at right angles. The thumb indicates the direction of normal. The magnetic field has an orienting action on the frame with a current. The frame is installed in a magnetic field so that its normal coincides with the direction of the power lines of the magnetic field.

Magnetic Moment The frame with current is called the vector equal to the product of the current strength flowing over the frame, on the square of the square.

The direction coincides with the direction. Directly defined by the rule of right hand.

Because A frame with a current is experiencing a field orient effect, a pair of forces acts on it in a magnetic field. Rotary torque depends on the properties of the field at this point

both from the properties of the frame

Vector magnetic induction, is a power quantitative characteristic of the magnetic field.

Magnetic Induction Unit - Tesla

If at this magnetic field to make various frames with a current having magnetic moments p. 1 P. 2 ... P. n. then the torque will be for each frame different M. 1 , M. 2 ... M. n. , but attitude

for all frames the same and can serve as a magnetic field characteristic.

Magnetic induction At this point of the homogeneous magnetic field, it is numerically equal to the maximum torque acting on a frame with a magnetic moment equal to one, when normal to the frame is perpendicular to the field direction. (Determine also with the help of the force of Lorentz or the force of the ampere).

The direction of the vector coincides with the direction of the vector case when the frame is in the equilibrium position.

The magnetic field is convenient to represent with the help of vector lines. Power linethe vector is called such a line tangent to which at any point coincides with the direction of the vectors of this point. The direction of power lines is vectorly determined by the rule of the right hand. For a rectilinear conductor: a thumb in the current direction, bent four fingers will indicate the direction of the power line. For a circular turn with current: four fingers - in the direction of current, the thumb indicates the direction of the power line in the center of the turn.

Magnetic induction lines, in contrast to vector power lines, electric field, are always closed and covered with current conductors. (The power lines are vector in positive charges and ends on negative, suitable perpendicular to the surface of the charge, the thickness of the power lines characterizes the size of the field).

In some cases, along with the vector used vector of magnetic field strength, which is associated with a vector relationship

µ 0 – magnetic constant; ,

µ - magnetic permeability environment - shows how many times the magnetic field in the medium is greater (less) the magnetic field in vacuo.

where IN - magnetic field in substance, IN 0 - external magnetizing field.

From the comparison of the vector characteristics of the electric field (vector and vectors) and the magnetic field (vector) it follows that the vector of the electrical field is similar to the magnetic induction vector. And the other determines the power effects of the fields and depend on the properties of the environment in which the fields are created.

Analogue of an electrical displacement vector is the magnetic field strength vector. The magnetic field of macrovok (Makrotoki - currents flowing through the conductors), therefore does not depend on the properties of the medium.

(Tesla);

2. Magnetic interaction of constant currents. Ampere Law. Lorentz power.

2. Interaction of currents.

If you include two wires in the DC circuit, then:

Consistently included parallel close-based conductor are repelled.

Parallel conductor included are attracted.

3. Mechanical exposure of current.

The magnetic arrow deflects near the conductor through which the current flows.

The frame is rotated with the current if the current is skipped through the conductor.

A magnetic field. All specified experimental facts indicate that in space surrounding a permanent magnet or a wire with a current, an magnetic field occurs, which has a power effect on test bodies (permanent magnets or conductor with current). By analogy with the tension of the electrical field E, it is possible to enter the concept of the magnetic induction vector. At each point of space, you can set the direction of the vector B, considering it by definition that it coincides with the direction from the southern pole freely suspended at this point of the magnetic arrow space.

Solid lines tangent to which at each point coincide with the direction of the magnetic induction vector in, are called the power lines of the magnetic field.

As simple experiments show, the power lines of the magnetic field are always closed. This magnetic field is fundamentally different from the electric field, the power lines of which always begin and

complete on charges. The closedness of the magnetic field lines is a consequence of the absence of isolated magnetic poles in nature.

Vector fields, the power lines of which are closed, are called vortex fields. Magnetic field - vortex.

Magnetic fields from different sources at this point of space are addressed according to the rule of formation of vectors (superposition principle)

Ampere Law. Let the conductor with the current entered into the region of the magnetic field. This conductor acts the force, the direction and the magnitude of which is determined by the AMPER's law:

It is convenient to use to determine the direction of the ampere force of the left hand.

Among the formula of the Amphere's law it follows that the ampere force reaches the maximum value of Fmas at q \u003d p / 2, i.e. when the conductor is located perpendicular to the magnetic induction vector.

The magnitude of the magnetic induction vector B is defined as the ratio F Max / IDL; in other words,

The unit of magnetic induction is determined from this formula and is equal to the magnetic induction of such a homogeneous field, in which the force of 1 H is valid for a period of conductor 1 M at a current in the conductor 1 A: [B] \u003d N / (A · M) \u003d TL (Tesla ).

Lorentz power. On the point electrical charge q moving at a speed V in a magnetic field induction in, acting from the side of the field Lorentz

Movement of the charged particle in a magnetic field. Let the initial velocity V of the charged particle are directed perpendicular to the magnetic induction vector in a permanent field. The Lorentz power f L \u003d QVB is directed perpendicular to both vectors V B and therefore does not change the particle speed module, and therefore constant itself. Under Newton's law, the centripetric acceleration created by the permanent force, directed perpendicular to the particle speed, causes the particle to move around the circle.

(13.2)

Cyclic frequency of rotation of the circle (cyclotron frequency)

(13.3)

It should be noted that this frequency does not depend on the velocity of the particle.

In the general case, when the initial particle speed is not perpendicular to the magnetic induction, the particle moves along the screw line (the trajectory is hung on the power lines of the field).

Hall effect. The deviation of the particles in the magnetic field allows us to prove on the experience that negatively charged electrons are negatively charged electrons.

The essence of the Hall effect is that if you place a conductor into an external homogeneous magnetic field, then between the opposite side surfaces of the conductor, perpendicular to the field lines of the field, there will be a small potential difference. It is due to the fact that the current carriers in the conductor are deflected in opposite sides (depending on the charge sign), and there is a violation of the charges of charges on opposite surfaces. Obviously, the signs of carrier charges determine the sign of the potential difference U Hall. Experience convincingly confirms that the carriers are electrons, and not some positively charged particles.

3. The principle of superposition of magnetic fields. The Bio-Savara-Laplace law as a result of the generalization of experimental data and as a result of the theory of relativity.

Magnetic induction of the field created by the conductor element by which the current flows? at some point BUT The position of which is determined by the element with a radius-vector, is under the law of Bio-Savara Laplace:

- Law of Bio-Savara Laplace

(in vector form)

Because In the law of Bio-Savara Laplas there is a vector product, then vector

Must be perpendicular to the plane of vectors and. The direction of the vector is the rule of right hand.

The module (value) of the vector is equal

- Law of Bio-Savara Laplace

(in a scalar form)

where α is the angle between and.

Principle of superposition of fields:

The magnetic induction of the resulting field created by several currents (or moving charges) is equal to a geometric (vector) amount of magnetic induction created by each current separately.

4. Application of the Bio-Savara-Laplace Law to calculate the magnetic field of the infinite linear current.

Application of the Bio-Savara-Laplace law to the calculation of magnetic fields.

a) magnetic field of direct current

; ;

Since induction created by various elementary areas, which we broke the conductor, at this point has the same direction, we can be replaced by scalar summation:

- magnetic induction of the straight line conductor of the final length.

- the tension of the magnetic field of the conductor of the final length.

In the case of an infinitely long conductor

b) magnetic field in the center of a circular conductor with a current

α \u003d 90 °; SIN α \u003d 1.

5. Magnetic field on the axis of the circular conductor with a current. Magnetic field in the center of the circular conductor with a current.

Consider the field created by the current I.flowing by a thin wire having a circle of radius R. (Fig. 1.7).

We define the magnetic induction on the axis of the conductor with the current at a distance h. From the circular plane. The vectors are perpendicular to the planes passing through the corresponding. Therefore, they form a symmetrical conical fan. From the consideration of symmetry, it can be seen that the resulting vector-made along the axis of the circular current. Each of the vector is equal to equal, Avzaimno is destroyed. But, and because The angle of betweenα - direct, turningid it

,

Substituting in (1.6.1) and, injecting over the entire contour, we get an expression for finding magnetic induction of circular tok. :

Note that in the numerator (1.6.2) - the magnetic moment of the contour. Then, at a high distance from the contour, with, magnetic induction can be calculated by the formula:

Power lines of the magnetic field of circular current are clearly visible in the experiment with iron sawdust (Fig. 1.8).

6. The vortex character of the magnetic field. The theorem on the circulation of the tension of the magnetic field and the induction vector of the magnetic field. Application of full current law for magnetic field in vacuum

Magnetic induction lines continuous: They have no beginning, no end. This takes place for any magnetic field caused by any contours with current. Vector fields with continuous lines, got a name vortex fields. We see that the magnetic field has a vortex field. This is the significant difference between the magnetic field from the electrostatic field. Magnetic field circulation theorem - One of the fundamental theorems of classical electrodynamics, formulated by Andre Marie Ampera in 1826. In 1861, James Maxwell again led this theorem, based on the analogies with the hydrodynamics, and summarized it (see below). The equation representing the content of the theorem in this generalized form is among the Maxwell equations. (For the case of permanent electric fields - that is, in principle, in the magnetostatics, the theorem in the original form, formulated by the ampere and the first one in the article, is first; for a general case, the right part must be supplemented with a member with a derivative of the electric field tension in time - see below). Theorem says:

This theorem, especially in foreign or translation literature, is also called ampere theorem or aMPER AMPER ON CIRCULATION (English. Ampère's Circuital Law). The latter name implies consideration of the AMPER's law as a more fundamental assertion than the Bio-Savara law - Laplace, which in turn is considered already as a consequence (which, in general, corresponds to a modern version of the construction of electrodynamics).

For a general case (classical) electrodynamics of the formula must be supplemented in the right part of a member containing time-derived from the electric field (see Maxwell equations, as well as paragraph "Generalization" below). In such an upward form, it represents the fourth equation of Maxwell in an integral form.

7. Work on the movement of the conductor and the circuit with the current in the magnetic field.

For a conductor with a current in a magnetic field, forces are valid, which are determined by the Ampherent Act. If the conductor is not fixed (for example, one of the sides of the contour is made in the form of a moving jumper, Fig. 1), then under the action of the force of the amper, it will move in the magnetic field. So, the magnetic field makes the work of the conductor with the current. To calculate this work, consider the conductor length l. With current I (it can move freely), which is placed in a homogeneous external magnetic field, which is perpendicular to the contour plane. The force, the direction of which is determined by the rule of the left hand, and the value according to the AMPER's law is calculated by the formula under the action of this force, the conductor will move in parallel to itself on the section DX from position 1 to position 2. Work that is performed by a magnetic field is equal to since l.dX \u003d DS is an area that crosses the conductor when it moves in a magnetic field, BDS \u003d DF - the flow of the magnetic induction vector, which permeates this area. Therefore, (1) i.e., work on the movement of the conductor with a current in a magnetic field is equal to the product of the current for the magnetic flux crossed by a moving conductor. This formula is also valid for arbitrary vector direction IN. Let us calculate the work on the movement of a closed loop with a constant current I in a magnetic field. We will assume that the contour M moves in the drawing plane and as a result of infinitely small displacement goes to position M ", shown in Fig. 2 of the dashed line. The current direction in the circuit (clockwise) and the magnetic field (perpendicular to the drawing plane - for the drawing or From us) Dana in the figure. Contour M Conditionally spread into two conductor connected by its ends: ABS and CDA. DA operation, which is performed by an amper with the study of the contour in a magnetic field, is equal to the algebraic amount of work on the movement of the AVS conductors (DA 1) and CDA (DA 2), i.e. (2) The forces that are applied to the CDA section of the circuit form sharp corners with the direction of movement, so the operation of DA 2\u003e 0 is performed... Using (1), we find this work is equal to the work Current strength I in our circuit on the CDA conductor intersected by the CDA conductor. CDA conductor crosses with its movement DF 0 through the surface performed in color, and the DF 2 stream that permeates the contour In its final position. So, (3) the forces that act on the AUT area of \u200b\u200bthe contour form blunt angles with the direction of movement, which means the work performed by them Da 1<0. Проводник AВС пересекает при своем движении поток dФ 0 сквозь поверхность, выполненную в цвете, и поток dФ1, который пронизывает контур в начальном положении. Значит, (4) Подставляя (3) и (4) в (2), найдем выражение для элементарной работы: где dФ 2 -dФ 1 =dФ" - изменение магнитного потока сквозь площадь, которая ограничена контуром с током. Таким образом, (5) Проинтегрировав выражение (5), найдем работу, которая совершается силами Ампера, при конечном произвольном перемещении контура в магнитном поле: (6) значит, работа по перемещению замкнутого контура с током в магнитном поле равна произведению силы тока в контуре на изменение магнитного потока, сцепленного с контуром. Выражение (6) верно для контура любой формы в произвольном магнитном поле.

8. Magnetic field and magnetic dipole moment of circular current. Magnetic magnetic. Magnetic field strength.

The magnetic moment of the turn with current is a physical value, like any other magnetic moment, characterizes the magnetic properties of this system. In our case, the system represents a circular twine with a current. This current creates a magnetic field that interacts with an external magnetic field. It can be both the field of land and the field of permanent or electromagnet.

Figure - 1 Circular Tock with Current

Circular twine with current can be represented as a short magnet. Moreover, this magnet will be directed perpendicular to the plane of the cooler. The location of the poles of such a magnet is determined using the Brasser rule. According to which the northern plus will be behind the plane of the cooler, if the current in it will move clockwise.

Figure 2 Imaginary strip magnet on the axis of the coat

On this magnet, that is, on our circular twine with a current, like on any other magnet, an external magnetic field will affect. If this field is homogeneous, then the torque will arise, which will strive to deploy the turn. The field will turn the coil so that its axis is located along the field. At the same time, the power lines of the spin itself, as a small magnet, should coincide in the direction with the external field.

If the external field is not uniform, then the transit movement will be added to the torque. This movement arises due to the fact that the fields of the field with greater induction will attract our magnet in the form of a turn more than sections with less induction. And the coil will start moving towards the field with greater induction.

The magnitude of the magnetic moment of the circular turn with the current can be determined by the formula.