MBOU Lokotskaya secondary school No. 1 named after. P.A. Markova
on this topic
« Magnetic flux. Electromagnetic induction"
Teacher Golovneva Irina Aleksandrovna
Lesson type: combined
Lesson Objectives:
Educational: to study the physical features of the phenomenon of electromagnetic induction, to form the concepts: electromagnetic induction, induction current, magnetic flux.
developing: to form in students the ability to highlight the main and essential in the material presented in different ways, development cognitive interests and abilities of schoolchildren in identifying the essence of the processes.
educational : to cultivate diligence, a culture of behavior, accuracy and clarity in answering, the ability to see the physics around you.
Lesson objectives
Tutorials:
to study the phenomenon of electromagnetic induction and the conditions for its occurrence;
consider the history of the issue of communication magnetic field and electric;
show cause-and-effect relationships when observing the phenomenon of electromagnetic induction,
contribute to the actualization, consolidation and generalization of the acquired knowledge, independent construction of new knowledge.
Developing: promote the development of the ability to work in a team, express their own opinions and argue their point of view.
Educational:
promote the development of cognitive interests of students;
contribute to the modeling of one's own system of values based on the idea of self-development.
The sequence of presentation of new material
magnetic flux.
The history of the discovery of the phenomenon of electromagnetic induction.
Demonstration of Faraday's experiments on electromagnetic induction.
Practical application of the phenomenon of electromagnetic induction.
Equipment
Collapsible transformer, galvanometer, permanent magnet, rheostat, ammeter, magnetic needle, key, connecting wires, generator model, multimedia projector, audio recording, presentation on the topic.
Lesson plan.
1. Organizational moment.
2. Actualization of knowledge.
In previous lessons, we examined the magnetic field and the characteristics of the magnetic field, its effect on a conductor with current and on a moving charge.
1. What is the source of the magnetic field?
2.What physical quantity is a characteristic of a magnetic field?
3. What are the rules for determining the direction of the magnetic induction vector?
Today the topic of our lesson is “Magnetic flux. Discovery of the phenomenon of electromagnetic induction "
We have to consider the following questions:
1. Magnetic flux.
2. The history of the discovery of the phenomenon of electromagnetic induction.
3. Demonstration of Faraday's experiments on electromagnetic induction.
4. Significance of the discovery of the phenomenon of electromagnetic induction.
3. Learning new material
( Presentation slides, interactive whiteboard, equipment for demonstrating experiments, audio recording are used).
1. Magnetic flux (definition, methods of change, dimension, formula). Repetition of 9th grade. Securing with presentation slides.
1. Study electromagnetic phenomena shows what's around electric current there is always a magnetic field. (Demonstration of Oersted's experience). Electric current and magnetic field are related to each other.
But if an electric current "creates" a magnetic field, isn't there a reverse phenomenon? Is it possible to "create" an electric current with the help of a magnetic field? This task was set by the English scientist M. Faraday in 1821.
On the screen is a portrait of M. Faraday (1791 - 1867).
The teacher, against the background of music, introduces the life and work of Faraday.
Faraday worked on this task for 10 years. He discovered electromagnetic induction - a new phenomenon, which he studied in detail and described in a number of articles. Faraday's discovery was a new step in the study of electromagnetic phenomena.
2. To understand how Faraday was able to "turn magnetism into electricity", let's perform some of Faraday's experiments using modern instruments. (Experiments are demonstrated and analyzed)
a) Faraday discovered that if we take two wire windings (we will take two coils) and change the current strength in one of them, for example, by closing or opening the circuit of the primary coil, then a current appears in the secondary coil, despite the fact that the coils are isolated from each other from friend. The phenomenon of excitation of an electric current in a closed conductor using a magnetic field is called electromagnetic induction. The current excited in this way is called induction current.
Showing my experience:
The occurrence of an induction current in a closed coil when the current is turned on and off in the second coil;
The occurrence of an induction current in a closed coil when the current strength is changed using a rheostat in the second coil;
The occurrence of an induction current when the coils move relative to each other.
We carry out the experiment with devices: a coil connected to a galvanometer, a magnet.
Conclusion: in all the cases considered, the induction current arose when the magnetic flux, penetrating the area of the coil covered by the conductor, changed.
We carry out the drawing according to the experiments. (Drawings on the board).
Consolidation of the studied material and control of knowledge.
Performed test work
Reflection.
Students have emoticons on their tables (smiling, indifferent and sad). The teacher asks to pick up the one that is more in line with the mood of each student in the lesson.
Today we got acquainted with the phenomenon of electromagnetic induction, which is used in all modern generators that convert mechanical energy into electrical. This phenomenon, discovered by M. Faraday in 1831, played a decisive role in technological progress. modern society. It is the physical basis of modern electrical engineering, providing industry, transport, communications, agriculture, construction and other industries, the life of people with electrical energy.
Thanks to everyone for being active in class. Estimates.
§ 8, 9 No. 838 (Rymkevich)
Appendix
Exercise. Read the biography of M. Faraday and fill in the table reflecting the contribution of the scientist to the discovery of the phenomenon of electromagnetic induction. Use textbooks, encyclopedias, books, electronic editions, Internet resources, other sources.
| Last name, first name, years of life | Photograph or pictorial portrait | Countries in which he worked | Main contribution into science | Opening symbol or a drawing of the installation on which the scientist worked |
| Contributions to other branches of physics |
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| What was most striking in the biography |
||||
LESSON PLAN
Theme “Magnetic flux. The phenomenon of electromagnetic induction, grade 9
Lesson Objectives:
The goal is to achieve educational outcomes.
Personal results:
– development of cognitive interests, intellectual and creative abilities;
– independence in acquiring new knowledge and practical skills;
– formation of value attitudes towards learning outcomes.
Metasubject results:
– mastering the skills of independent acquisition of new knowledge, organization learning activities, goal setting, planning;
- mastering the methods of action in non-standard situations, mastering heuristic methods for solving problems;
- the formation of skills to observe, to highlight the main thing, to explain what is seen.
Subject Results:
– know: magnetic flux, induction current, electromagnetic induction phenomenon;
– understand: the concept of flow, the phenomenon of electromagnetic induction
– be able to: determine the direction of the induction current, decide typical tasks OGE.
Lesson type: learning new material
Lesson form: study lesson
Technology: technology elements critical thinking, problem learning, ICT, problematic dialogue technology
Lesson equipment: computer, interactive whiteboard, coil, tripod with foot, bar magnet - 2 pcs., demonstration galvanometer, wires, device for demonstrating Lenz's rule.
During the classes
Start: 10.30
1. Organizational stage(5 minutes).
Hello guys! Today I will conduct a physics lesson, my name is Innokenty Innokentevich Malgarov, a physics teacher at the Kyllakh school. I am very glad to work with you, with high school students, I hope today's lesson will be productive. At today's lesson attentiveness, independence, resourcefulness are estimated. The motto of our lesson with you is “Everything is very simple, you just need to understand!”. Now, the roommates look at each other, wish good luck and shake hands. For feedback, I will sometimes clap my hands, and you will repeat. Let's check? Amazing!
Please look at the screen. What do we see? That's right, a waterfall and a strong wind. What word (one!) combines these two natural phenomena? Yes, flow. Water flow and air flow. Today we will also talk about flow. Only about a stream of a completely different nature. Can you guess what? What are the topics that you have previously covered? That's right, magnetism. Therefore, write down the topic of the lesson in your worksheets: Magnetic Flux. The phenomenon of electromagnetic induction.
Start: 10.35
2. Actualization of knowledge (5 minutes).
Exercise 1. Please look at the screen. What can you say about this picture? Fill in the blanks on the worksheets. Consult with a partner.
1. Around the conductor with current arises a magnetic field. It is always closed;
2. The force characteristic of the magnetic field is magnetic induction vector 0 "style="border-collapse:collapse;border:none">
Look at the screen. By analogy, fill in the second column for the contour in a magnetic field.
Look at the demonstration table, please. On the table you see a rack with a movable rocker with two aluminum rings. One whole, and the other - with a slot. We know that aluminum does not exhibit magnetic properties. We begin to introduce the magnet into the ring with a slot. Nothing happens. Now let's start introducing the magnet into the whole ring. Pay attention, one hundred ring begins to "run away" from the magnet. We stop the movement of the magnet. The ring also stops. Then we begin to carefully remove the magnet. Now the ring starts to follow the magnet.
Try to explain what you see (students try to explain).
Please look at the screen. There is a hint hidden here. (Students come to the conclusion that by changing the magnetic flux, you can get an electric current).
Task 4. It turns out that if you change the magnetic flux, you can get an electric current in the circuit. You already know how to change the flow. How? That's right, you can strengthen or weaken the magnetic field, change the area of the contour itself and change the direction of the contour plane. Now I will tell one story. You listen carefully and do task 4 in parallel.
In 1821, the English physicist Michael Faraday, inspired by the work of Oersted (the scientist who discovered the magnetic field around a conductor with current), set himself the task of obtaining electricity from magnetism. For almost ten years he carried wires and magnets in his trouser pocket, unsuccessfully trying to get an electric current out of them. And one day, quite by accident, on August 28, 1831, he succeeded. (Prepare and show a demonstration). Faraday found that if the coil is quickly put on (or removed from) a magnet, then a short-term current arises in it, which can be detected using a galvanometer. This phenomenon has been called electromagnetic induction.
This current is called by induction current. We said that any electric current generates a magnetic field. The induced current also creates its own magnetic field. Moreover, this field interacts with the field of a permanent magnet.
Now using interactive whiteboard, determine the direction of the induction current. What conclusion can be drawn regarding the direction of the magnetic field of the induction current?
Start: 11.00
5. Application of knowledge in various situations (10 minutes).
I suggest you solve the tasks that are offered in the OGE in physics.
Task 5. A strip magnet is brought to a solid aluminum ring suspended on a silk thread at a constant speed (see figure). What will happen to the ring at this time?
1) the ring will remain at rest
2) the ring will be attracted to the magnet
3) the ring will be repelled by the magnet
4) the ring will begin to rotate around the thread
Task 6.
1) Only in 2.
2) Only in 1.
4) Only in 3.
Start: 11.10
5. Reflection (5 minutes).
It's time to evaluate the results of our lesson. What have you learned? Were the goals that were set at the beginning of the lesson achieved? What was difficult for you? What did you especially like? What feelings did you experience?
6. Information about homework
Find in your textbooks the topic “Magnetic flux”, “The phenomenon of electromagnetic induction”, read and see if you can answer the questions for self-examination.
Thank you again for your cooperation, for your interest and, in general, for a very interesting lesson. I wish you to study physics well and, on its basis, to learn the structure of the world.
“It’s very simple, you just need to understand!”
Surname, name of the student _______________________________________ 9th grade student
Date "____" ________________2016
WORKSHEET
Lesson topic: _________________________________________________________________
__________________________________________________________________________
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Task 4. Fill the gaps.
1. The phenomenon of the occurrence of current in a closed conductor (circuit) when the magnetic field penetrating this circuit changes is called _______________________;
2. The current that occurs in this circuit is called _____________________;
3. The magnetic field of the circuit created by the induction current will be directed to __________________ of the magnetic field of the permanent magnet (Lenz's Rule).
https://pandia.ru/text/80/300/images/image006_55.jpg" align="left hspace=12" width="238" height="89"> Task 6. There are three identical metal rings. A magnet is removed from the first ring, a magnet is inserted into the second ring, and a fixed magnet is located in the third ring. In which ring does the induced current flow?
1) Only in 2.
2) Only in 1.
Lesson topic:
Discovery of electromagnetic induction. magnetic flux.
Target: introduce students to the phenomenon of electromagnetic induction.
During the classes
I. Organizational moment
II. Knowledge update.
1. Frontal survey.
- What is Ampère's hypothesis?
- What is magnetic permeability?
- What substances are called para- and diamagnets?
- What are ferrites?
- Where are ferrites used?
- How do you know that there is a magnetic field around the Earth?
- Where are the North and South magnetic poles of the Earth?
- What processes take place in the Earth's magnetosphere?
- What is the reason for the existence of a magnetic field near the Earth?
2. Analysis of experiments.
Experiment 1
The magnetic needle on the stand was brought to the lower and then to the upper end of the tripod. Why does the arrow turn towards the lower end of the tripod from either side south pole, and to the upper end - the northern end?(All iron objects are in the Earth's magnetic field. Under the influence of this field, they are magnetized, and the lower part of the object detects the north magnetic pole, and the top is south.)
Experiment 2
In a large cork stopper, make a small groove for a piece of wire. Lower the cork into the water, and put the wire on top, placing it along the parallel. In this case, the wire, together with the cork, is rotated and installed along the meridian. Why?(The wire has been magnetized and is set in the Earth's field like a magnetic needle.)
III. Learning new material
Between moving electric charges operate magnetic forces. Magnetic interactions are described based on the concept of a magnetic field that exists around moving electric charges. Electric and magnetic fields are generated by the same sources - electric charges. It can be assumed that there is a connection between them.
In 1831, M. Faraday confirmed this experimentally. He discovered the phenomenon of electromagnetic induction (slides 1.2).
Experiment 1
We connect the galvanometer to the coil, and we will put forward a permanent magnet from it. We observe the deviation of the galvanometer needle, a current (induction) has appeared (slide 3).
The current in the conductor occurs when the conductor is in the area of \u200b\u200bthe alternating magnetic field (slide 4-7).
Faraday imagined an alternating magnetic field as a change in the number lines of force penetrating the surface bounded by the given contour. This number depends on the induction AT magnetic field, from the contour area S and its orientation in the given field.
F \u003d BS cos a - magnetic flux.
F [Wb] Weber (slide 8)
The induction current can have different directions, which depend on whether the magnetic flux penetrating the circuit decreases or increases. The rule for determining the direction of the induced current was formulated in 1833. E. X. Lenz.
Experiment 2
We slide a permanent magnet into a light aluminum ring. The ring is repelled from it, and when extended, it is attracted to the magnet.
The result does not depend on the polarity of the magnet. Repulsion and attraction is explained by the appearance of an induction current in it.
When the magnet is pushed in, the magnetic flux through the ring increases: the repulsion of the ring at the same time shows that the induction current in it has such a direction in which the induction vector of its magnetic field is opposite in direction to the induction vector of the external magnetic field.
Lenz's rule:
The inductive current always has such a direction that its magnetic field prevents any changes in the magnetic flux that cause the appearance of an inductive current.(slide 9).
IV. Conducting laboratory work
Laboratory work on the topic "Experimental verification of the Lenz rule"
Devices and materials:milliammeter, coil-coil, arcuate magnet.
Working process
- Prepare a table.
« Physics - Grade 11 "
Electromagnetic induction
The English physicist Michael Faraday was confident in the unified nature of electrical and magnetic phenomena.
A time-varying magnetic field generates an electric field, and a changing electric field generates a magnetic field.
In 1831, Faraday discovered the phenomenon of electromagnetic induction, which formed the basis for the device of generators that convert mechanical energy into electric current energy.
The phenomenon of electromagnetic induction
The phenomenon of electromagnetic induction is the occurrence of an electric current in a conducting circuit, which either rests in a magnetic field that changes in time, or moves in a constant magnetic field in such a way that the number of magnetic induction lines penetrating the circuit changes.
For his numerous experiments, Faraday used two coils, a magnet, a switch, a direct current source and a galvanometer.
An electric current can magnetize a piece of iron. Can a magnet cause an electric current?
As a result of experiments, Faraday found main features phenomena of electromagnetic induction:
one). induction current occurs in one of the coils at the moment of closing or opening electrical circuit another coil, fixed relative to the first.
2) induction current occurs when the current strength in one of the coils changes with the help of a rheostat 
3). induced current occurs when the coils move relative to each other 
4). induction current occurs when a permanent magnet moves relative to the coil 
Conclusion:
In a closed conducting circuit, a current arises when the number of magnetic induction lines penetrating the surface bounded by this circuit changes.
And the faster the number of lines of magnetic induction changes, the greater the resulting induction current.
It doesn't matter though. which is the reason for the change in the number of lines of magnetic induction.
This may also be a change in the number of lines of magnetic induction penetrating the surface bounded by a fixed conducting circuit, due to a change in the current strength in the adjacent coil,
and a change in the number of induction lines due to the movement of the circuit in an inhomogeneous magnetic field, the density of lines of which varies in space, etc.
magnetic flux
magnetic flux- this is a characteristic of the magnetic field, which depends on the vector of magnetic induction at all points of the surface bounded by a flat closed contour. 
There is a flat closed conductor (circuit) bounding the surface with area S and placed in a uniform magnetic field.
Normal (vector whose modulus equal to one) to the plane of the conductor makes an angle α with the direction of the magnetic induction vector
The magnetic flux Ф (flux of the magnetic induction vector) through a surface with an area S is a value equal to the product of the modulus of the magnetic induction vector by the area S and the cosine of the angle α between the vectors and:
Ф = BScos α
where
Bcos α = B n- projection of the magnetic induction vector on the normal to the contour plane.
So
Ф = B n S
The magnetic flux is greater, the more In n and S.
The magnetic flux depends on the orientation of the surface that the magnetic field penetrates.
The magnetic flux can be graphically interpreted as a quantity proportional to the number of lines of magnetic induction penetrating a surface with an area S.
The unit of magnetic flux is weber.
Magnetic flux in 1 weber ( 1 Wb) is created by a uniform magnetic field with an induction of 1 T through a surface of 1 m 2 located perpendicular to the magnetic induction vector.
The topic of today's lesson is devoted to an important topic - "Magnetic flux". To begin with, we recall what electromagnetic induction is. After that, we will talk about what causes the induction current and what is the main thing for this current to appear. From Faraday's experiments, we learn how a magnetic flux arises.
Continuing the study of the topic "Electromagnetic induction", let's take a closer look at such a concept as magnetic flux.
You already know how to detect the phenomenon of electromagnetic induction - if a closed conductor is crossed magnetic lines, an electric current is generated in this conductor. Such a current is called inductive.
Now let's discuss how this electric current is generated and what is the main thing for this current to appear.
First of all, let's turn to Faraday's experience and look again at its important features.
So, we have an ammeter, a coil with a large number turns, which is short-circuited to this ammeter.
We take a magnet, and in the same way as in the previous lesson, we lower this magnet into the coil. The arrow deviates, that is, there is an electric current in this circuit.
Rice. 1. Experience in detecting induction current
But when the magnet is inside the coil, there is no electric current in the circuit. But as soon as you try to get this magnet out of the coil, an electric current reappears in the circuit, but the direction of this current changes to the opposite.
Please also note that the value of the electric current that flows in the circuit also depends on the properties of the magnet itself. If you take another magnet and do the same experiment, the value of the current changes significantly, in this case the current becomes smaller.
After conducting experiments, we can conclude that the electric current that occurs in a closed conductor (in a coil) is associated with the magnetic field of a permanent magnet.
In other words, the electric current depends on some characteristic of the magnetic field. And we have already introduced such a characteristic -.
Recall that magnetic induction is denoted by the letter, it is a vector quantity. And the magnetic induction is measured in Tesla.
Tesla - in honor of the European and American scientist Nikola Tesla.
Magnetic induction characterizes the effect of a magnetic field on a current-carrying conductor placed in this field.
But, when we talk about electric current, we must understand that electric current, and you know this from grade 8, arises under the action of electric field.
Therefore, we can conclude that the electric induction current appears due to the electric field, which in turn is formed as a result of the magnetic field. And such a relationship is just carried out due to magnetic flux.
What is magnetic flux?
magnetic flux denoted by the letter Ф and expressed in units such as weber, and denoted by .
Magnetic flux can be compared to the flow of a liquid flowing through a limited surface. If you take a pipe, and liquid flows in this pipe, then, accordingly, a certain flow of water will flow through the cross-sectional area of \u200b\u200bthe pipe.
The magnetic flux, by this analogy, characterizes how many magnetic lines will pass through a limited circuit. This contour is the area bounded by a wire coil or, perhaps, by some other form, while this area is necessarily limited.
Rice. 2. In the first case, the magnetic flux is maximum. In the second case, it is equal to zero.
The figure shows two turns. One turn is a wire turn through which the lines of magnetic induction pass. As you can see, there are four of these lines. If there were much more of them, then we would say that the magnetic flux would be large. If there were fewer of these lines, for example, we would draw one line, then we could say that the magnetic flux is small enough, it is small.
And one more case: when the coil is located in such a way that magnetic lines do not pass through its area. It seems that the lines of magnetic induction slide over the surface. In this case, we can say that there is no magnetic flux, i.e. there are no lines that would penetrate the surface of this contour.
magnetic flux characterizes the entire magnet as a whole (or another source of magnetic field). If magnetic induction characterizes the action at any one point, then the magnetic flux is the entire magnet. We can say that the magnetic flux is the second very important characteristic of the magnetic field. If magnetic induction is called the power characteristic of the magnetic field, then the magnetic flux is the energy characteristic of the magnetic field.
Returning to the experiments, we can say that each turn of the coil can be represented as a separate closed turn. The same circuit through which the magnetic flux of the magnetic induction vector will pass. In this case, an inductive electric current will be observed.
Thus, it is under the influence of the magnetic flux that an electric field is created in a closed conductor. And already this electric field creates nothing more than an electric current.
Let's look again at the experiment, and now, already knowing that there is a magnetic flux, let's look at the relationship between the magnetic flux and the value of the inductive electric current.
Let's take a magnet and pass it slowly enough through the coil. The value of the electric current changes very little.
If you try to pull out the magnet quickly, then the value of the electric current will be greater than in the first case.
In this case, the rate of change of the magnetic flux plays a role. If the change in the speed of the magnet is large enough, then the induction current will also be significant.
As a result of such experiments, the following regularities were revealed.
Rice. 3. What determines the magnetic flux and induction current
1. Magnetic flux is proportional to magnetic induction.
2. The magnetic flux is directly proportional to the surface area of the circuit through which the lines of magnetic induction pass.
3. And the third - the dependence of the magnetic flux on the angle of the circuit. We have already paid attention to the fact that if the area of the contour in one way or another, it affects the presence and magnitude of the magnetic flux.
Thus, we can say that the strength of the induction current is directly proportional to the rate of change of the magnetic flux.
∆ F is the change in the magnetic flux.
∆ t is the time during which the magnetic flux changes.
The ratio is just the rate of change of the magnetic flux.
Based on this dependence, we can conclude that, for example, an induction current can also be created by a fairly weak magnet, but the speed of movement of this magnet must be very high.
The first person who received this law was the English scientist M. Faraday. The concept of magnetic flux allows a deeper look at the unified nature of electrical and magnetic phenomena.
List of additional literature:
Elementary textbook of physics. Ed. G.S. Landsberga, T. 2. M., 1974 Yavorsky BM, Pinsky AA, Fundamentals of Physics, vol. 2., M. Fizmatlit., 2003 Do you know flows so well?// Kvant. - 2009. - No. 3. - S. 32-33. Aksenovich L. A. Physics in high school: Theory. Tasks. Tests: Proc. allowance for institutions providing general. environments, education / L. A. Aksenovich, N. N. Rakina, K. S. Farino; Ed. K. S. Farino. - Mn .: Adukatsy i vykhavanne, 2004. - P.344.
