Open lesson on physics in 11th grade.
General lesson: “Electromagnetic
induction"
Developed by a physics teacher at Sokolchinsky Secondary School No. 3
Kholmogorova A.A.
Item. Physics class 11th grade
Lesson topic General lesson on the topic: “Electromagnetic induction”
Lesson Objectives Educational
1.Summarize and systematize students’ knowledge of the given topic.
2. Investigate the dependence of the induction current on the magnetic flux. Developmental
Form logical thinking, the ability to research, analyze, and draw conclusions. Educational
Foster feelings of collectivism,
Accuracy and respect for the computer.
The type of ICT used in the lesson “Open Physics” part 2, which allows you to study the phenomenon of electromagnetic induction using interactive computer models, testing the acquired knowledge in the form of computer testing.
Organizational structure of the lesson.
Lesson stage Teacher activity Student activity
1. Updating knowledge Formulates questions that update basic knowledge on the topic of the lesson.
1.What is the phenomenon of electromagnetic induction? By whom and when was this phenomenon discovered?
2.Use the drawing to determine the direction of the induction current in the conductor
3.Formulate the law of electromagnetic induction.
4.What force is called the Lorentz force? How to determine its direction?
5. The figure shows a closed conductor moving in a uniform magnetic field. Determine the direction of the induction current.
6.What is the phenomenon of self-induction?
7. In what units is inductance expressed? (After the answer, you can tell the story of why the writer took the pseudonym O Henry)
8.Write the formula for finding the energy of the magnetic field of the current. They join the business rhythm of the lesson, answer questions, and take notes.
One student is at the blackboard, the rest in a notebook determine the direction of the induction current.
Write down the formula, give a definition. Using the rule, find the direction.
1 Gn
Research work. The teacher suggests looking at computer models. See Attachment. Study the computer model using the “Open Physics Part 2” disk. Draw conclusions and answer questions in the application.
Control and self-test of knowledge. The teacher offers to test students’ knowledge on this topic using a test from “Open Physics Part 2” “Electromagnetic Induction.” They test their knowledge in the form of computer testing. Receive information about the actual results of the exercise.
Reflection. The teacher mobilizes students to evaluate their activities during the lesson. They reflect on their activities in the lesson and conduct a self-assessment of their results. Answer the questions:
1. Did you like the lesson?
Application.
In the electromagnetic induction section, open a window showing a diagram of the movement of a conductor in a uniform magnetic field.
- Press the start button. Observe how the magnetic flux changes and how long it took for this change to occur. Write down the formula for calculating the induced emf. Calculate the emf and compare the result with the data.
-In this figure, determine the direction of the induction current and write it down.
2. Open the window of the Faraday experiment model1.
- Lower and raise the magnet, first slowly and then quickly. Do the same with the coil. In which case does the magnetic flux change faster? Draw a conclusion.
3. Open the window of the Faraday experiment model2. Consider the model.
How does the current change when the primary winding closes and opens? Why is there a short current pulse in the indicator coil?
4. Open the test from the “Electromagnetic induction” section. Write down the answers to the questions in your notebook, and do the necessary calculations in your notebook. Justify your answers.
5. Summing up.
-answer the following questions:
Reflection. 1. Did you like the lesson?
2.What moments of the lesson do you find most interesting?
3.What difficulties did you experience in the lesson?
4.Comments and suggestions for the future.
Summary lesson:
"Electromagnetic
induction"
Kholmogorova A.A.
Lesson stage | Teacher activities | Student activities |
1.Updating knowledge | ||
Research work. | ||
Reflection. | 1. Did you like the lesson? |
Application.
1.
5. Summing up.
Reflection.
1. Did you like the lesson?
2.What moments of the lesson do you find most interesting?
3.What difficulties did you experience in the lesson?
4.Comments and suggestions for the future.
Download:
Preview:
Open lesson on physics in 11th grade.
Summary lesson:
"Electromagnetic
induction"
Developed by a physics teacher at Sokolchinsky Secondary School No. 3
Kholmogorova A.A.
Organizational structure of the lesson.
Lesson stage | Teacher activities | Student activities |
1.Updating knowledge | Formulates questions that update basic knowledge on the topic of the lesson. 1.What is the phenomenon of electromagnetic induction? By whom and when was this phenomenon discovered? 2.Use the drawing to determine the direction of the induction current in the conductor 3.Formulate the law of electromagnetic induction. 4.What force is called the Lorentz force? How to determine its direction? 5. The figure shows a closed conductor moving in a uniform magnetic field. Determine the direction of the induction current. 6.What is the phenomenon of self-induction? 7. In what units is inductance expressed? (After the answer, you can tell the story of why the writer took the pseudonym O Henry) 8.Write the formula for finding the energy of the magnetic field of the current. | They join the business rhythm of the lesson, answer questions, and take notes. One student is at the blackboard, the rest in a notebook determine the direction of the induction current. Write down the formula and give a definition. The rule is to find the direction. 1 Gn |
Research work. | The teacher suggests looking at computer models. See Attachment. | Study the computer model using the “Open Physics Part 2” disk. Draw conclusions and answer questions in the application. |
Control and self-test of knowledge. | The teacher suggests testing students’ knowledge on this topic using a test from “Open Physics Part 2” “Electromagnetic Induction” | They test their knowledge in the form of computer testing. Receive information about the actual results of the exercise. |
Reflection. | The teacher mobilizes students to evaluate their activities during the lesson. | They reflect on their activities in the lesson and conduct a self-assessment of their results. Answer the questions: 1. Did you like the lesson? 2.What moments of the lesson do you find most interesting? 3.What difficulties did you experience in the lesson? 4.Comments and suggestions for the future. |
Application.
- In the electromagnetic induction section, open a window showing a diagram of the movement of a conductor in a uniform magnetic field.
Press the start button. Observe how the magnetic flux changes and how long it took for this change to occur. Write down the formula for calculating the induced emf. Calculate the emf and compare the result with the data.
In this figure, determine the direction of the induction current and write it down.
2. Open the window of the Faraday experiment model1.
Lower and raise the magnet, first slowly and then quickly. Do the same with the coil. In which case does the magnetic flux change faster? Draw a conclusion.
3. Open the window of the Faraday experiment model2. Consider the model.
How does the current change when the primary winding closes and opens? Why is there a short current pulse in the indicator coil?
4. Open the test from the “Electromagnetic induction” section. Write down the answers to the questions in your notebook, and do the necessary calculations in your notebook. Justify your answers.
5. Summing up.
Answer the following questions:
Reflection.
1. Did you like the lesson?
2.What moments of the lesson do you find most interesting?
3.What difficulties did you experience in the lesson?
4.Comments and suggestions for the future.
Lesson objectives:
- Testing and consolidating students' knowledge on this topic.
- Development of knowledge systematization skills.
- Fostering a sense of responsibility for your studies.
Equipment:
- Ceramic magnets.
- Lenz device.
- Galvanometer, coil, arc-shaped magnet.
- Alternator.
- Constructor “Geomag”.
- Didactic materials “A.E. Maron 11th grade.”
- Disc “Lessons of Cyril and Methodius” 10th grade lessons No. 28-31.
During the classes
I. Welcome, introduction to the lesson plan.
1. Hello guys, today we will have a general lesson on the topic “Magnetic field. Electromagnetic induction". Guests present at the lesson are physics teachers from our region. They also have wonderful students like you, they will worry and worry about you, so let's answer calmly and confidently.
2. Guys, at the end of today's lesson you will all receive grades. This grade will be derived from the arithmetic average of the three grades you must receive during the lesson. You will receive your first mark for telling a rule or explaining a formula. You will earn a second mark for solving a problem on the board or explaining experiments that I will demonstrate and which you will see on the screen. You will receive the third grade for tests that contain three tasks.
3. Guys, before we start work, let's remember what we know today about the most ordinary magnets?
Answer: Magnet in translation means “loving stone”; people have been treated with magnets for a long time, the soul was prescribed to magnets; a magnet has two poles.
II. Check of knowledge.
1. Explaining the rules and explaining the formulas. (They are written on the board in advance)
Rules: gimlet, left hand, Lenz
Definition: phenomena of electromagnetic induction, self-induction
Fa=B|I| L sin a
Fл=|q|vB sin a
Ф=BS cos a
E=vBL sin a
Eis=-L I/t
Wm=LI * I/2
3. On the board there are drawings for the problems - students go out one by one and find the unknown quantity.
4. The teacher shows experiments, the children explain (they have already seen these experiments in previous lessons)
a) with ceramic magnets – interaction of magnets;
b) Lenz device - the phenomenon of electromagnetic induction;
c) galvanometer, coil, magnet - the appearance of alternating electric current;
d) generator - the light comes on.
5. Footage is shown on the screen, students explain what they are talking about
6. Question: what is common between self-induction and inertia?
7. What rule we learned does the following picture resemble? See Appendix 1
8. Working with tests from didactic material.
| № | 1 | 2 | 3 |
| IN 1 | IN | A | A |
| AT 2 | IN | B | B |
After 5 minutes I show the correct answers and the rating scale.
III. Summarizing.
- We give ourselves grades and take the arithmetic average.
- We hand in sheets of marks.
IV. Summarizing the lesson, thanking the students for their good work.
VI. Homework:
Prepare a message about the use of all the forces and the phenomenon that we have repeated today in modern technology.
State budgetary professional educational institution of the Republic of Crimea "Dzhankoy Vocational College"»
Development of an open lesson
in physics
Generalization and systematization of knowledge on the topic:
"A magnetic field. Electromagnetic induction"
Developed by: Physics teacher
Ashimova G.A.
2016
Lesson topic: Generalization and systematization of knowledge on the topic: “Magnetic field. Electromagnetic induction"
Lesson objectives:
Educational : repeat, summarize and systematize knowledge on the topic: “Magnetic field. Electromagnetic induction"; contribute to the improvement of previously acquired knowledge
Developmental : promote the development of cognitive interest, mental activity and creative abilities of students; promote the development of memory, logical thinking, attentiveness, the ability to define and explain concepts, analyze and generalize, be critical of your answers and the answers of your comrades, as well as the ability to use theoretical knowledge when solving problems.
Educational : promote a sense of responsibility, independence, conscientiousness, maximum work capacity, foster the ability to work in a team, the ability to listen to one’s comrades and draw conclusions, foster positive motivation for acquiring knowledge, its practical usedirection.
Lesson type : a lesson in generalizing and systematizing knowledge.
Lesson form : intellectual game “Conquest to the Peaks of Knowledge”
Teaching methods: verbal, visual, practical.
Forms of training: group form of training and individual form of training.
Elements of educational technologies:
information and communication technologies,
problem-based learning technology,
level differentiation technology,
gaming technologies.
TCO, handout: computer,multimedia projector, interactiveblackboard, lesson presentation, videos of experiments: “The Ampere Force”, “The Work of the Ampere Force”, “Faraday’s Experiment”, “The Phenomenon of Self-Induction”; didactic handouts.
Technological lesson map
Lesson stageStage tasks
Forms of organization of educational activities
Teacher's activities
Student activities
I . Organizing time
Create a working spirit among students and ensure a business-like atmosphere in the classroom.
Greets, checks readiness for the lesson, motivates educational work, informs the topic of the lesson and work plan.
Greet the teacher and get acquainted with the handouts on the tables. Students independently formulate lesson goals(Appendix No. 1-Self-assessment sheet)
II . Repetition and generalization of knowledge
Stage 1 – “Warm-up”.
Updating of reference knowledge Testing(Appendix No. 2)
Self-control of knowledge
Review previously acquired knowledge about the magnetic field and electromagnetic induction.
Individual
Demonstrates questions for test assignments on presentation slides, comments on assignments, explains, and announces evaluation criteria.
After students answer, announces the correct answers and sums up.
Students answer test questions. Then they give themselves a grade on the self-assessment sheet.
Scoring Criteria
For every 4 correct answers, 1 point is awarded, maximum 5 points
Stage 2 – “Explain”experience ». (Appendix No. 3)
Repeat, deepen and comprehend previously studied material, highlight basic knowledge in this topic. Learn to find cause-and-effect relationships and draw conclusions
Individual
Video clips are shown - “The Power of Ampere”, “Ampere force work", "Faraday's experiment", "Self-induction phenomena"
Explains the purpose of the work, asks questions, draws students’ attention to the main conclusions and laws, leads students to understand the practical application of the acquired knowledge, and evaluates the answers.
Questions:
What is Ampere power?
How to determine the direction of the Ampere force?
How to determine the work done by the Ampere force?
What is electromagnetic induction?
Conditions for the occurrence of induction current.
Definition of self-induction.
Why does the light bulb not immediately stop glowing after turning off the circuit?.
Why does one of the lamps light up later than the other?
Where are these phenomena used in practice?
Students explain the experience and answer additional questions.
For the correct answer - 1 point.
Stage 3 – Physical dictation (Appendix No. 4)
Review basic concepts and quantitieson this topic
Individual, steam room
Invites students to answer questions. The task and time limit are repeated twice. After recording their answers, students are asked to check the assignment.
Students are invited to raise their hands - those who received grades “5”, then “4”, “3” and those with dashes. In this way, the teacher finds out the level of students’ performance of the dictation.
They answer physical dictation questions, carry out mutual checks, and put their assessment on the self-assessment sheet.
To do this, students exchange notebooks with their desk neighbor, hand out sheets with the correct answers, then write “+” in the margins if the answer is correct and “-” if the answer is incorrect.
Evaluation criteria:
For 9-10 correct answers – score “5” For 7-8 correct answers – score “4” For 5-6 correct answers – score “3” Less than 5 correct answers – score “2”»
Stage 4 - “Find the mistake!”
Group work
Repeat basic formulas on the topic studied
Group
Distributes the task to the groups, explains the procedure for completing it, evaluates the students' answers.
A series of formulas are written on the board. The groups are given sheets with formulas. There were errors in four of the five formulas. The students' task is to find errors and point to the correct entry of the formula.
Time limit: 5 minutes
Then the group goes to the board, takes turns pointing out errors or asserting that the formula is written correctly. The group earns as many points as there are correct answers.Students put their grades on a knowledge control sheet.
Stage 5 – Problem solving - ( Appendix No. 5 ).
There is an expression on the board: Knowing physics means being able to solve problems. (Enrico Fermi)
Groups receive differentiated tasks.
Groups have the right to choose a task
Repeat the application of the basic laws on this topic when solving problems.
Group
Formulates the goal of this stage, motivates students’ activities in solving problems, explains the choice of type of problems, checks the correctness of the solution and design of problems, and sums up the results.
Solve problems in notebooks independently. Then one of the students goes to the board and writes down the solution to the selected problem.
Students give grades on the knowledge control sheet.
III . Lesson summary.
Psummarize the lesson, evaluate the work
Individual
Provides instructions for calculating the average grade and sums up the work of students and the lesson.
Studentscalculate the average score for the lesson and hand over the control sheet to the teacher.
Grading for the lesson.
Evaluation criteria:
“5” - 24.25 points
“4” - 20-23 points
“3” - 15-19 points
“2” - less than 15 points
IV .Homework:
(Appendix No. 6)
Announces homework:
Create a crossword puzzle on the topic: “Magnetic field. Electromagnetic induction".
Fill out the table: “Comparative characteristics of the properties of magnetic and electric fields”(Appendix No. 6)
Write down homework in a notebook
Reflection (Appendix No. 7)
Conduct reflection, assess your mood
Individual
Invites students to conduct reflection (motivation and methods of activity) - Set the flags on the poster with the image of the mountain “Peak of Knowledge”
Analyze and evaluate their work in class. Attach flags to a poster with the image of the mountain “Peak of Knowledge”
Appendix No. 1
Assessment sheet
F.I. studentLesson stages; assessment method
Individual work
Group work
Warm-up (testing)
(self-control)
(maximum 5 points)
2. Explain the experience
(estimates
teacher)
( maximum - 5 points )
3. Physical
dictation
(mutual control)
( maximum - 5 points)
4. “Find the mistake”
(evaluated by the teacher)
( maximum - 5 points)
5. Problem solving
(evaluated by the teacher
( maximum - 5 points)
General
point
Lesson grade
Evaluation criteria:
“5” - 24.25 points
“4” - 20-23 points
“3” - 15-19 points
“2” - less than 15 points.
Appendix 2
Test on the topic: “Magnetic field. Electromagnetic induction"
1. What is the source of the magnetic field?
A) a stationary charged particle;IN) any charged body;
WITH) any moving body;D) a moving charged particle.
2. What is the main characteristic of a magnetic field?
A) magnetic flux;B)
Ampere power;
C) Lorentz force;D) vector of magnetic induction.
3. Choose a formula for calculating the magnitude of the magnetic induction vector.
A) ;B) ;
C) ;
D) .
4. Indicate the direction of the magnetic field induction vector at point A, located on the axis of the circular current. (Fig. 1).
Fig.1
A) to the right;B) left;C) to us;D) from U.S;E) up;F) down.
5. Select the formula for the modulus of the Ampere force vector.
A);B) ;
C) ;
D) .
6. In Fig. 2, the arrow indicates the direction of the current in the conductor located between the poles of the magnet. In what direction will the conductor move?
Fig.2
A) to the right;B) left;C) to us;D) from U.S;E) up;F) down.
7. How does the Lorentz force act on a particle at rest?
A) acts perpendicular to the magnetic induction vector;
B) acts parallel to the magnetic induction vector;
C) It does not work.
8. At what point in the figure (see Fig. 3) does the magnetic field of the current flowing through the conductor MN act on the magnetic needle with the least force?
Fig.3
A) At point A;B) At point B;C)At point B.
9. How do two parallel conductors interact if electric current flows in them in opposite directions?
A) The interaction force is zero.
C) Conductors attract.
C) The conductors repel.
10. How do two coils interact (see Fig. 4) when currents in the indicated directions pass through them?
Fig.4
A) attract;B) are repelled;C) do not interact.
11.
What is the phenomenon of the occurrence of electric current in a closed circuit when the magnetic flux through the circuit changes?
A) Electrostatic induction.B) The phenomenon of magnetization.
C) Self-inductionD)Electrolysis. E) Electromagnetic induction.
12. Who discovered the phenomenon of electromagnetic induction?
A)X. Oersted.B)Sh. Pendant.C) A. Volta.
D) A. Ampere.E) M. Faraday.F) D. Maxwell.
13.What is the name of the physical quantity equal to the product of the module B of the magnetic field induction by the area S of the surface penetrated by the magnetic field and the cosine
angle a between the vector B of induction and the normal n to this surface?
A) Inductance.B) Magnetic flux.C) Magnetic induction.
D) Self-induction.E) Magnetic field energy.
14. Which of the following expressions determines the induced emf in a closed loop?
A) B) C) D) E)
15. When a strip magnet is pushed into and out of a metal ring, an induced current occurs in the ring. This current creates a magnetic field. Which pole faces the magnetic field of the current in the ring towards: 1) the retractable north pole of the magnet and 2) the retractable north pole of the magnet.
A)1 - northern, 2 - northern.B) 1 - southern, 2 - southern.
C) 1 - southern, 2 - northern.D) 1 - northern, 2 - southern.
16. The unit of measurement of what physical quantity is 1 Weber?
A) Magnetic field induction.B)Electrical capacity.
C)Self-induction.D) Magnetic flux.E) Inductance.
17. What is the name of the unit of measurement of inductance?
A) Tesla.B) Weber.C)Gauss.D) Farad.E) Henry.
18. What expression determines the relationship between the magnetic flux energy in a circuit and inductance L circuit and current strength I in the circuit?
A).B). C) LI 2 , D) LI
19 . The induced current arising in a closed circuit with its magnetic field counteracts the change in the magnetic flux that caused it - this is ...
A) Right hand rule.B) Left hand rule.
C) Gimlet rule.D) Lenz's rule.
20 . Two identical lamps are connected to a DC source circuit, the first in series with a resistor, the second in series with a coil. In which of the lamps (Fig. 5) will the current strength, when switch K is closed, reach its maximum value later than the other?
rice. 5
A) In the first.
B) In the second.
C) In the first and second at the same time.
D) In the first, if the resistance of the resistor is greater than the resistance of the coil.
E) In the second, if the coil resistance is greater than the resistor resistance.
Appendix No. 3
Exercise "Explain the experience"
Videos of experiments: Ampere force, work of Ampere forces, Faraday's experiment, the phenomenon of self-induction.
Description of experiments
ExperienceWork of Ampere forces.
Under the action of the Ampere force, the conductor moves in one direction or another depending on the direction of the current, and, therefore, the force does work.
Self-induction experience.
Two light bulbs are connected to a current source, one through a rheostat, the other through an inductor. When the key is closed, you can see that the light bulb connected through the rheostat lights up earlier. A light bulb connected through an inductance coil lights up later, since a self-inductive emf arises in the coil, which prevents the current from changing. If you frequently close and open the circuit, then the light bulb connected through the inductor does not have time to light up.
Experience.
Ampere power.
When current is passed through a conductor located in a magnetic field, it is acted upon by a force directed perpendicular to the magnetic field lines. When the direction of the current is changed, the direction of the force is reversed.
F= Iblsin
Faraday's experiment.
When a magnet is inserted into a coil connected to an ammeter, an induced current appears in the circuit. When removed, an induced current also appears, but in a different direction. It can be seen that the induced current depends on the direction of movement of the magnet and which pole introduces it. The current strength depends on the speed of the magnet.
Appendix 4
Physical dictation, designed for 8-10 minutes, is intended for assessing knowledge on “MAGNETIC FIELD. ELECTROMAGNETIC INDUCTION"
Physical dictation consists ofAndt of 10 basic physical terms, phenomena, formulas, and 10 questions about them.
(The student himself chooses the correct answer, in his opinion, and puts the number of his answer opposite the number of the question)
I OPTIONQuestion
Answer
1
MICHAEL FARADAY
№__
2
AMPERE
№__
3
INDUCTANCE
№__
4
MAGNETIC INDUCTION
№__
5
LORENTZ FORCE
№__
6
SELF-INDUCTION
№__
7
A MAGNETIC FIELD
№__
8
SOLENOID
№__
9
ELECTROMAGNETIC INDUCTION
№__
10
INDUCTION CURRENT
№__
OPTION II
Question
Answer
1
INDUCTION CURRENT
№__
2
ELECTROMAGNETIC INDUCTION
№__
3
SOLENOID
№__
4
A MAGNETIC FIELD
№__
5
SELF-INDUCTION
№__
6
LORENTZ FORCE
№__
7
MAGNETIC INDUCTION
№__
8
INDUCTANCE
№__
9
AMPERE
№__
10
MICHAEL FARADAY
№__
QUESTIONS FOR PHYSICAL DICCTATION
Details
By type, this is a lesson in studying and consolidating new material, which is conducted as a research lesson. The lesson uses a multimedia presentation. This lesson uses individual and collective forms of learning organization. During the lesson, the verbal method was used, the visual method was the illustration method (poster) and the demonstration method (experience, presentation), as well as the problem presentation method. During the lesson, student-centered learning is used.
The lesson introduces the basic concepts of electrodynamics: electromagnetic induction, induced current, the relationship between magnetic and electric fields. The lesson uses activity-based learning technology, the main emphasis is on students’ independent work to acquire new knowledge. A problematic situation is created. Schoolchildren know that a magnetic field appears around a current-carrying conductor. Can a magnetic field produce an electric current?
During the lesson, a differentiated approach was used in the form of a multi-level test.
Lesson topic: “The phenomenon of electromagnetic induction”
Lesson type: lesson on comprehensive acquisition of knowledge, skills, abilities
Teaching methods: explanatory-illustrative, reproductive, partially search.
Forms of organization of cognitive activity:
· frontal (frontal conversation at all stages of the lesson);
· group
Lesson objectives:
· educational: to study the phenomenon of electromagnetic induction and the conditions for its occurrence, to show cause-and-effect relationships when observing the phenomenon of electromagnetic induction, to promote the actualization, consolidation and generalization of acquired knowledge, and the independent construction of new knowledge;
· developing: promote the development of the ability to work in a group, develop logical thinking and attention, the ability to analyze, compare the results obtained, and draw appropriate conclusions.
· educational: to cultivate cognitive need and interest in the subject;
Equipment: strip magnet, connecting wires, galvanometer, milliammeter, coils, current source, key, coil, arc-shaped magnet, rheostat, transformer, device for demonstrating electric welding.
On the board: a poster indicating the stages of the class
During the classes
Organizing time
Good afternoon, students. I welcome you to today’s physics lesson, which I, Elena Nikolaevna Luneva, will teach, and you will help me with this. The topic of our lesson is “The phenomenon of electromagnetic induction.” Please write down the topic of the lesson in your notebook. State the goals and objectives of the lesson. Our lesson will be held under the motto: “Remember - look - draw conclusions - share ideas.” On your tables there are cards with pictures of little people, which we will use at the end of the lesson.
Reflection: they looked at each other and smiled, looking into each other’s eyes.
Work on the topic of the lesson
Motivation and updating of knowledge.
1. The figure shows three points: A, M, N. In which of them will the magnetic field of the current flowing through the conductor BC act on the magnetic needle with the greatest force, with the least force?
2. A current of the indicated direction is passed through a coil, inside of which there is a steel rod. Determine the poles of the resulting electromagnet. How can you change the position of the poles of this electromagnet? 
3. The figure shows two bare conductors connected to a current source and a lightweight aluminum tube AB. Determine the direction of the current in the tube AB if, as a result of the interaction of this current with the magnetic field, the tube rolls along the conductors in the direction indicated in the figure. Which pole of the current source is positive and which is negative? 
4. The figure shows a wire circuit placed in a uniform magnetic field. At what orientation of the circuit in relation to the lines of magnetic induction is the magnetic flux penetrating the area of this circuit maximum and equal to zero? 
5.Explain Oersted's experiment. 
Formulation of the problem.
1820 Oersted concluded: “Electricity gives rise to magnetism.”
What do you think: “Can magnetism generate electricity”?
Many scientists tried to solve this problem at the beginning of the 19th century. The English scientist M. Faraday also put it before himself. In 1822 He wrote in his diary “Convert magnetism into electricity.”
What needs to be done to obtain an electric current from a magnetic field?
Listen to students' statements.
It took M. Faraday almost 10 years to solve it.
Faraday's experiment: a coil connected to a galvanometer, a magnet is brought closer to this coil and removed.
What do you observe as the magnet approaches the coil?
Why did the needle deviate?
The magnet is in the coil, what do you see?
Why didn't the needle deviate?
We remove the magnet from the coil, what do we observe? Why did the arrow deviate? In which direction did the arrow deviate?
Why does current occur in the coil?
Is it possible to change the current value?
How? What do I need to do?
What conclusion can be drawn from this experience?
Conclusion: Electric current arises when the number of magnetic induction lines penetrating a closed circuit changes.
We have considered only one way of generating electric current. There are several other ways to generate electric current. And now you and I will work in groups and solve experimental problems.
Work in groups.
Group 1: strip magnet, connecting wires, milliammeter, coil.
Task: Bring the magnet closer to the coil and move the magnet away from the coil.
What are you observing?
Why did electric current arise?
What will happen if you attach a magnet and start moving the coil relative to the magnet?
Group 2: current source, two coils (one is inserted into the other), connecting wires, milliammeter, key.
Lock the key. Move one coil relative to another coil. What are you observing?
Close and open the key and watch what happens?
Why did electric current occur in the circuit?
Draw a conclusion from your experiments.
Group 3: current source, rheostat, 2 coils with an iron core, connecting wires, milliammeter.
Slowly move the rheostat slider and observe whether an electric current will appear in the circuit?
Why does electric current occur?
Now move the rheostat slider faster. What can you say about the current value?
Draw a conclusion from your experiments.
Group 4: two magnets fixed in stands, a wire frame, connecting wires, a milliammeter.
Rotate the frame slowly between the poles of the magnet. What will happen?
At what moments does the milliammeter needle deviate?
Why does current appear and then disappear in the frame?
Draw a conclusion from your experience.
Discussion of the experiment results
Methods for producing electric current.
Movement of a magnet relative to a coil;
Movement of the coil relative to the magnet;
Closing and opening the circuit;
Rotation of the frame inside the magnet;
Moving the rheostat slider;
The movement of one coil relative to another.
This current is called induction; its name indicates only the cause of the current.
Causes of electric current.
1. When the magnetic flux penetrating the area covered by the conductor changes;
2. By changing the current strength in the circuit;
3. By changing the orientation of the circuit relative to the lines of magnetic induction.
Guys, let's draw a general conclusion from the demonstrated experiments.
Conclusion: In a closed circuit that is placed in an alternating magnetic field, an electric current arises if and only if the number of lines of force penetrating the circuit changes.
The phenomenon that we discussed is called electromagnetic induction.
Definition: The phenomenon of electromagnetic induction is the occurrence of an induced current in a conducting circuit, which is either at rest in a time-varying magnetic field or moving in a constant magnetic field, such that the number of magnetic induction lines penetrating the circuit changes.
4. Application of electromagnetic induction.
The discovery of electromagnetic induction is one of the most remarkable scientific achievements of the first half of the 19th century. It caused the emergence and rapid development of electrical engineering and radio engineering. Electromagnetic induction is used in modern technology: metal detectors, electrodynamic microphones, in magnetic levitation trains, in household microwave ovens, reading video and audio information from magnetic tapes.
Faraday was the first to construct an imperfect model of an electric current generator that converts mechanical rotational energy into current, consisting of a copper disk rotating between the poles of a strong magnet. The current recorded by the galvanometer was weak, but the most important thing was done: the principle of constructing a current generator was found. You will study the design and principle of operation of the generator in the next lesson.
Electromagnetic induction is used in various technical devices and instruments. Let's consider such a device - it is a transformer.
A transformer is a device used to increase or decrease alternating voltage.
Transformer structure: magneto - soft steel core, on which two coils with wire windings are placed. The primary winding is connected to an alternating voltage source, the secondary winding is connected to the load.
Experience: 1. Connect a light bulb to the secondary winding of the transformer. Show how the light bulb lights up when we remove the core connecting the windings and when we short the coils with the core.
What are you observing? Why does the light bulb burn weaker in the first case than in the second case?
2. Remove the secondary coil from the transformer and instead of this coil, put and remove a wire coil on the rod, first without a core.
What are you observing?
Then close the circuit with the core.
What are you observing? Why does the light bulb burn brighter?
3. Instead of the second coil, we use a device to demonstrate welding. Show how a spark appears and how the electrodes melt.
Consolidation of the studied material.
What did we learn in today's lesson?
What is the phenomenon of electromagnetic induction?
What conditions are necessary for the existence of the phenomenon of electromagnetic induction?
In what ways can induced current be obtained?
What determines the magnitude of the induction current?
Summarizing. Homework.
1. § 49, exercise 39
2. Design creative works
