Lesson topic electromagnetic field electromagnetic waves. Lesson summary. Electromagnetic waves

06.11.2019

State budget professional educational institution Samara region "Provincial technical school m. R. Koshkinsky

Profession: 23.01.03 Auto mechanic 2 course

Physics

METHODOLOGICAL DEVELOPMENT OF A LESSON

ON THIS TOPIC: "ELECTROMAGNETIC WAVES IN OUR LIFE»

Teacher Yakimova Elvira Konstantinovna

Lesson-generalization of the topic "Electromagnetic waves"

Topic:ALL ABOUT ELECTROMAGNETIC WAVES

Type: generalization and systematization of knowledge

Type: seminar

Methodological goal:

Target:

Show the practical orientation of teaching physics;

Checking the assimilation of knowledge on the topic.

Tasks:

educational:

Generalize knowledge about electromagnetic radiation (fields) encountered in everyday life;

Find out the positive and negative effects of these fields on human organism,

Form the principles of protection from the harmful effects of fields, or reduce their harmful effects.

developing:

Continue development logical thinking- the ability to correctly formulate one's thoughts in the process of summarizing what has been learned, the ability to conduct an educational dialogue;

educational:

Raising a cognitive interest in physics, a positive attitude towards knowledge, careful attitude to health.

Nurture a culture oral speech, respect for others.

Methodical equipment and equipment:

multimedia equipment, household appliances, worksheets; reference materials(meaning

strength of magnetic induction electro magnetic field household appliances)

Methods: explanatory-illustrative, practical.

Lesson on the topic: " All about electromagnetic waves "

“Around us, in ourselves, everywhere and everywhere,

forever changing, coinciding and colliding,

radiation of different wavelengths...

The face of the earth is changing

they are largely sculpted. ”

V.I.Vernadsky

What is an electromagnetic wave?

Answers: Electromagnetic wave- electromagnetic oscillations propagating in space and carrying energy.

Electromagnetic waves are disturbances of magnetic and electric fields that are distributed in space.

Electromagnetic waves are called an electromagnetic field propagating in space with a finite velocity depending on the properties of the medium. The first scientist to predict their existence at all was Faraday. He put forward his hypothesis in 1832. The theory was later developed by Maxwell. By 1865 he completed this work. Maxwell's theory found its confirmation in the experiments of Hertz in 1888.

Waves are em waves.

Answer: K em. waves are waves,whose lengths range from 10 km (radio waves) to less than 5 pm (5.10 -12 ) (gamma rays)

3. List the main properties of electromagnetic waves.

Answer:

Refraction.

Reflection.

The EM wave is transverse.

The speed of em waves in vacuum is equal to the speed of light.

Electromagnetic waves propagate in all media, but the speed will be lower than in a vacuum.

The EM wave carries energy.

When passing from one medium to another, the frequency of the wave does not change.

4. Why does the electromagnetic field affect a person?

A person is an antenna that receives electromagnetic waves, the human body is a conductor through which the em field passes well, therefore, an additional electromagnetic field is superimposed on the natural electromagnetic oscillations of the body, due to which the natural human biofield is disturbed.

5. What does the biological effect of the electromagnetic field depend on?

Teacher: we take the worksheets again -

Independent work.

SCHEME 1

Answers: The biological effect depends on:

- values of E (electric field strength);

-values B (magnetic induction);

-values w (frequency), from the exposure time.

Teacher: The biological effect can be positive (the emergence of life on Earth, acceleration, methods of treatment in medicine) and negative. Doctors have found that a long stay in an artificially created electromagnetic field gives ...

(Table on the board).

Teacher: Did you feel such actions of the electromagnetic field and when? What household appliances create an electromagnetic field in your apartment?

Independent work.

Teacher: All operating electrical appliances (and electrical wiring) create an electromagnetic field around them, which causes the movement of charged particles: electrons, protons, ions or dipole molecules. The cells of a living organism are composed of charged molecules - proteins, phospholipids (molecules cell membranes), water ions - and also have a weak electromagnetic field. Under the influence of a strong electromagnetic field, molecules with a charge make oscillatory movements. This gives rise to a number of processes, both positive (improvement of cellular metabolism) and negative (for example, destruction of cellular structures).

In our country, studies of the influence of electromagnetic fields on humans and animals have been conducted for more than 50 years. After conducting hundreds of experiments, Russian scientists have found that all household electrical appliances are sources of electromagnetic radiation, but how exactly the electromagnetic field from ordinary household appliances affects us and how harmful it is to a healthy person is a moot point, so it is reasonable to try to minimize it as much as possible. impact.

To form the principles of protection against the harmful effects of electromagnetic radiation, students are invited to work with reference materials.

(

Application No. 2

Table 1. PDU (maximum permissible levels).

Table 2. How can you protect yourself from the harmful effects of an electromagnetic field, or at least reduce the biological effect?

Let's watch the presentation (from slide 11 to the end)

Summing up.

Conclusions:

1. Metal shielding of sources of electromagnetic radiation (wires, inductors, etc.),

2. Maintain a safe distance.

3. All household electrical appliances must be in good working order and comply with the remote control. (Certificate of quality).

4. Green spaces actively absorb electromagnetic waves.

A “Good to know” leaflet is distributed to each student.

Homework.

Teacher: Discuss with family at home"Good to know" noteat home, maybe your loved ones will add something useful and necessary to our memo.

List of used literature:

Maron A.E. tests in physics: 10 - 11 cells: A book for the teacher. – M.: Enlightenment, 2003.

Rymkevich A.P. Task book. Grades 10 - 11: A manual for educational institutions. – M.: Bustard, 2003.

Stepanova G.N. Collection of problems in physics: For 10 - 11 cells. educational institutions. – M.: Enlightenment, 2003.

5. ›

Municipal budgetary educational institution -

average comprehensive school No. 6 im. Konovalova V.P.

Klintsy, Bryansk region

Developed by a physics teacher of the first qualification category:

Sviridova Nina Grigorievna

Targets and goals:

Tutorials:

Introduce the concept of electromagnetic field and electromagnetic wave;

Continue the formation of correct ideas about the physical picture of the world;

To study the process of formation of an electromagnetic wave;

To study the types of electromagnetic radiation, their properties, application and effect on the human body;

Introduce the history of the discovery of electromagnetic waves

Develop skills in solving qualitative and quantitative problems.

Developing:

Development of analytical and critical thinking(the ability to analyze natural phenomena, the results of the experiment, the ability to compare and establish common and distinctive features, the ability to explore tabular data, the ability to work with information)

The development of students' speech

Educational

Education of cognitive interest in physics, a positive attitude to knowledge, respect for health.

Equipment: presentation; table "Scale of electromagnetic waves", worksheet-summary with tasks for teaching independent work, physical equipment.

Demonstration experiments and physical equipment.

1) Oersted's experience (current source, magnetic needle, conductor, connecting leads, key)

2) the effect of a magnetic field on a current-carrying conductor (current source, arcuate magnet, conductor, connecting leads, key)

3) phenomenon electromagnetic induction(coil, strip magnet, demonstration galvanometer)

Intersubject communications

Mathematics (solution of calculation problems);

History (a little about the discovery and study of electromagnetic radiation);

OBZH (rational and safe use of devices - sources of electromagnetic radiation);

Biology (the effect of radiation on the human body);

Astronomy (electromagnetic radiation of space).

1. Motivational stage -7 min.

Press conference "Electricity and Magnetism"

Teacher: Modern world, surrounding a person filled with a variety of technology. Computers and mobile phones, televisions have become our closest indispensable assistants and even replace our communication with friends. Numerous studies show that our assistants at the same time take away the most valuable thing from us - our health. Do your parents often wonder what causes more damage to a microwave oven or a cell phone?

We will answer this question later.

Now - a press conference on the topic "Electricity and Magnetism".

Students. Journalist: Known since antiquity, electricity and magnetism until the beginning of the 19th century were considered phenomena that were not related to each other, and were studied in different sections of physics.

Journalist: Externally, electricity and magnetism manifest themselves in completely different ways, but in fact they are closely related, and many scientists have seen this connection. Give an example of an analogy, or common properties electrical and magnetic phenomena.

Expert - physicist.

For example, attraction and repulsion. In electrostatics of opposite and like charges. In the magnetism of opposite and like poles.

Journalist:

The development of physical theories has always proceeded on the basis of overcoming contradictions between hypothesis, theory and experiment.

Journalist: B early XIX century, the French scientist Francois Arago published the book Thunder and Lightning. Does this book contain some of the most curious entries?

Here are some excerpts from the book "Thunder and Lightning": "... In June 1731, a merchant placed in the corner of his room in Wexfield a large box filled with knives, forks and other objects made of iron and steel ... Lightning penetrated house, just through the corner in which the box stood, broke it and scattered all the things that were in it. All those forks and knives... turned out to be highly magnetized...”)

What hypothesis could physicists put forward by analyzing excerpts from this book?

Expert - physicist: Objects were magnetized as a result of a lightning strike, at that time lightning was known to be an electric current, but theoretically at that time scientists could not explain why this happened.

Slide #10

Journalist: Experiments with electric current attracted scientists from many countries.

An experiment is a criterion for the truth of a hypothesis!

What experiments of the 19th century showed the connection between electrical and magnetic phenomena?

Expert - physicist. Demonstration experiment - Oersted's experiment.

In 1820, Oersted conducted the following experiment (Oersted's experiment, the magnetic needle turns near a current-carrying conductor) There is a magnetic field in the space around a current-carrying conductor.

In the absence of equipment, a demonstration experience can be replaced by a DER

Journalist. Oersted experimentally proved that electrical and magnetic phenomena are interconnected. Was there a theoretical justification?

Expert - physicist.

The French physicist Ampère in 1824 Ampère conducted a series of experiments and studied the effect of a magnetic field on current-carrying conductors.

Demonstration experiment - the effect of a magnetic field on a conductor with current.

Ampère was the first to combine two previously separated phenomena - electricity and magnetism - with one theory of electromagnetism and proposed to consider them as the result of a single process of nature.

Teacher: There was a problem: The theory was met with disbelief by many scientists!?

Expert physicist. Demonstration experiment - the phenomenon of electromagnetic induction (the coil is at rest, the magnet is moving).

In 1831, the English physicist M. Faraday discovered the phenomenon of electromagnetic induction and found out that the magnetic field itself is capable of generating an electric current.

Journalist. Problem: We know that current can occur in the presence of an electric field!

Expert - physicist. Hypothesis: The electric field arises as a result of a change in the magnetic field. But there was no proof of this hypothesis at that time.

Journalist: By the middle of the 19th century, a lot of information about electrical and magnetic phenomena had accumulated?

This information required systematization and information in a single theory, who created this theory?

Expert physicist. Such a theory was created by the outstanding English physicist James Maxwell. Maxwell's theory solved a number of fundamental problems of electromagnetic theory. Its main provisions were published in 1864 in the work "Dynamical Theory of the Electromagnetic Field"

Teacher: Guys, what will we study in the lesson, formulate the topic of the lesson.

Students formulate the topic of the lesson.

Teacher: Write down the topic of the lesson in the worksheet-outline, which we will work with today during the lesson.

Worksheet-summary of the lesson of a 9th grade student………………………………………………………………

Lesson topic:…………………………………………………………………………………………………………………………… …………….

1) Alternating electric and magnetic fields generating each other form a single……………………………………………………………………………………………………… ……………………………………………

2) Sources of electromagnetic field -………………….……………………charges,

moving with …………………………………………………

3) Electromagnetic wave…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………..................

4) Electromagnetic waves propagate not only in matter, but also in ……………………………..

5) Type of wave-……………………………………………

6) The speed of electromagnetic waves in vacuum is indicated by the Latin letter c:

with ≈………………………………………………

The speed of electromagnetic waves in matter ………………….than in vacuum…………

7) Wavelength λ=…………………………………………

What would you like to learn in the lesson, what goals will you set for yourself.

Students formulate the objectives of the lesson.

Teacher: Today in the lesson we will learn what an electromagnetic field is, expand our knowledge about the electric field, get acquainted with the process of the emergence of an electromagnetic wave and some properties of electromagnetic waves,

2. Actualization of basic knowledge-3min.

Frontal survey

1. What is a magnetic field?

2. What generates a magnetic field?

3. How is the magnetic induction vector designated? What are the units of measurement of magnetic induction.

4. What is an electric field. Where does the electric field exist?

5. What is the phenomenon of electromagnetic induction?

6. What is a wave? What are the types of waves? What is a transverse wave?

7. Write down the formula for calculating the wavelength?

3. Operational-cognitive stage-25 min

1) Introduction of the concept of electromagnetic field

According to Maxwell's theory, alternating electric and magnetic fields cannot exist separately: a changing magnetic field generates an alternating electric field, and a changing electric field generates an alternating magnetic field. These generating each other alternating electric and magnetic fields form a single electromagnetic field.

Work with the textbook - reading the definition page 180

Textbook definition: Any change over time in a magnetic field results in an alternating electric field, and any change over time in an electric field generates an alternating magnetic field.

ELECTROMAGNETIC FIELD

These generating each other alternating electric and magnetic fields form a single electromagnetic field.

Work with the outline plan (students supplement the outline in the process of studying new material).

1) Alternating electric and magnetic fields generating each other form a single ………………… (electromagnetic field)

2) Sources of electromagnetic field -……(electric) charges moving with…………………(acceleration)

The source of the electromagnetic field. Textbook page 180

The sources of the electromagnetic field can be:

Electric charge moving with acceleration, for example, oscillating (the electric field created by them changes periodically)

(unlike a charge moving at a constant speed, for example, in the case of a constant current in a conductor, a constant magnetic field is created here).

quality task.

What field arises around an electron if:

1) the electron is at rest;

2) moves at a constant speed;

3) moving with acceleration?

An electric field always exists around an electric charge, in any frame of reference, a magnetic field exists in the one relative to which electric charges move,

Electromagnetic field - in the frame of reference, relative to which electric charges move with acceleration.

2) Explanation of the mechanism of occurrence of the inductive current, e in the case when the conductor is at rest. (Solution of the problem formulated at the motivational stage during the press conference)

1) An alternating magnetic field generates an alternating electric field (vortex), under the influence of which free charges set in motion.

2) The electric field exists independently of the conductor.

Problem: Does the electric field created by an alternating magnetic field differ from the field of a stationary charge?

3) Maintaining the concept of tension, describing the lines of force of the electric field of the electrostatic and vortex, highlighting the differences. (Solution of the problem formulated at the motivational stage during the press conference)

Introduction of the concept of tension and lines of force of an electrostatic field.

What can you say about electrostatic field lines?

What is the difference between an electrostatic field and a vortex electric field?

The vortex field is not connected with the charge, the lines of force are closed. Electrostatic - associated with the charge, vortex - is generated by an alternating magnetic field and is not associated with the charge. General - electric field.

4)Introduction of the concept of an electromagnetic wave. Distinctive properties of electromagnetic waves.

According to Maxwell's theory, an alternating magnetic field generates an alternating electric field, which in turn generates a magnetic field, as a result, the electromagnetic field propagates in space in the form of a wave.

Keeping 3 definitions, first 2), then students read the definition in the textbook p. 182, write down the definition in the summary that you think is easier to remember or the one you like.

3) Electromagnetic wave…………….

1) is a system of generating each other, and propagating in space, alternating (vortex) electric and magnetic fields.

2) this is an electromagnetic field propagating in space with a finite speed, depending on the properties of the medium.

3) The perturbation of the electromagnetic field propagating in space is called an electromagnetic wave.

Properties of electromagnetic waves.

How are electromagnetic waves different from mechanical waves? See page 181 in the textbook and complete the summary of paragraph 4.

4) Electromagnetic waves propagate not only in matter, but also in ...... (vacuum)

If a mechanical wave propagates, then the vibrations are transmitted from particle to particle.

What oscillates in an electromagnetic wave? Like in a vacuum?

What kind physical quantities periodically change in it?

Over time, the intensity and magnetic induction change!

How are the vectors E and B oriented with respect to each other in an electromagnetic wave?

Is the electromagnetic wave longitudinal or transverse?

5) wave type………(transverse)

Electromagnetic wave animation

Velocity of electromagnetic waves in vacuum. Page 181 - find the numerical value of the speed of electromagnetic waves.

6) The speed of electromagnetic waves in vacuum is denoted by the Latin letter c: c ≈ 300,000 km/s=3*108 m/s;

What can be said about the speed of electromagnetic waves in matter?

The speed of electromagnetic waves in matter ……(less) than in vacuum.

For a time equal to the period of oscillation, the wave has moved a distance along the axis, equal to the length waves.

For electromagnetic waves, the same relationships between wavelength, speed, period and frequency are valid as for mechanical waves. The speed is indicated by the letter s.

7) wavelength λ= c*T= с/ ν.

Let's repeat and check the information about electromagnetic waves. Students compare the notes on the worksheets and on the slide.

Teacher: Any theory in physics must coincide with experiment.

Student's message. Experimental discovery of electromagnetic waves.

In 1888, the German physicist Heinrich Hertz experimentally obtained and registered electromagnetic waves.

As a result of Hertz's experiments, all the properties of electromagnetic waves theoretically predicted by Maxwell were discovered!

5) Study of the scale of electromagnetic radiation.

Electromagnetic waves are divided by wavelength (and, accordingly, by frequency) into six ranges: the boundaries of the ranges are very arbitrary.

Electromagnetic wave scale

low frequency radiation.

1.Radio waves

2.Infrared radiation (thermal)

3.Visible radiation (light)

4.UV radiation

5.X-rays

6.γ - radiation

Teacher: What information can be obtained by examining the scale of electromagnetic waves.

Students: From the drawings, you can determine which bodies are sources of waves or where electromagnetic waves are applied.

Conclusion We live in the world of electromagnetic waves.

What bodies are the sources of waves.

How does the wavelength and frequency change if you go on a scale from radio waves to gamma radiation?

Why do you think space objects are used as examples on this table.

Students. Astronomical objects (stars, etc.) emit electromagnetic waves.

Research and comparison of information on the scales of electromagnetic waves.

Compare 2 scales on a slide? What is the difference? What radiation is not on the second scale?

Why is there no low-frequency oscillations on the second one?

Student message.

Maxwell: to create an intense electromagnetic wave that could be registered by a device at a certain distance from the source, it is necessary that the oscillations of the intensity and magnetic induction vectors occur at a sufficiently high frequency (of the order of 100,000 oscillations per second or more). The frequency of the current used in industry and everyday life is 50 Hz.

Give examples of bodies emitting low-frequency radiation.

Student message.

The influence of low-frequency electromagnetic radiation on the human body.

Electromagnetic radiation with a frequency of 50 Hz, which is created by the wires of the AC mains, with prolonged exposure causes

Fatigue,

Headache,

Irritability,

fast fatigue,

Weakening of memory

Sleep disturbance…

Teacher: We pay attention to the fact that memory deteriorates if we work with a computer for a long time or watch TV, which prevents us from studying well. Let's compare the permissible norms of electromagnetic radiation radiation of household appliances, electric vehicles, etc. Which electrical appliances are more harmful to human health? Which is more dangerous microwave oven or cell phone? Does the power depend on the power of the device?

Student message. Rules to help keep you healthy.

1) The distance between electrical appliances should be at least 1.5-2 m. (In order not to increase the effect of household electromagnetic radiation)

Your beds should be the same distance from the TV or computer.

2) stay away from sources of electromagnetic fields as far as possible and for as little time as possible.

3) Turn off all non-working appliances from the sockets.

4) Turn on as few appliances as possible at the same time.

Let's explore another 2 scale of electromagnetic waves.

What radiation is present on the second scale?

Students: On the second scale, there is microwave radiation, but on the first scale, there is none.

Although the frequency range is notional, do microwaves refer to radio waves or infrared radiation on scale #1?

Students: Microwave radiation - radio waves.

Where are microwave waves used?

Student message.

Microwave radiation is called microwave radiation because it has the highest frequency in the radio range. This frequency range corresponds to wavelengths from 30 cm to 1 mm; therefore it is also called the range of decimeter and centimeter waves.

Microwave radiation plays a big role in life modern man, after all, we cannot refuse such achievements of science as mobile communications, satellite television, microwave ovens or microwave ovens, radar, the principle of operation of which is based on the use of microwaves.

Solution problematic issue set at the beginning of the lesson.

What do microwaves and cell phones have in common?

Students. The principle of operation is based on the use of microwave radio waves.

Teacher: Interesting information about the invention of the microwave oven can be found on the Internet - homework.

Teacher: We live in a "sea" of electromagnetic waves that radiates from the sun (the entire spectrum of electromagnetic waves) and other space objects - stars, galaxies, quasars, we must remember that any electromagnetic radiation can bring both benefit and harm. The study of the scales of electromagnetic waves shows us how great the importance of electromagnetic waves in human life.

6) Training independent work - work in pairs with the textbook pp. 183-184 and based on life experience. 5 test questions are mandatory for everyone, task 6 is a calculation task.

1. The process of photosynthesis occurs under the action

B) visible radiation-light

2. Human skin tans under the action

A) ultraviolet radiation

B) visible radiation-light

3. In medicine, during fluorographic examination,

A) ultraviolet light

B) X-ray radiation

4. For television communication use

A) radio waves

B) X-ray radiation

5. In order not to get a retinal burn from solar radiation, people use glass "sunglasses", since glass absorbs a significant part

A) ultraviolet radiation

B) visible radiation-light

6. On what frequency do ships transmit an SOS distress signal if, according to international agreement, the radio wave length should be 600m? The speed of propagation of radio waves in air is equal to the speed of electromagnetic waves in vacuum 3 * 108 m / s

4) Reflective-evaluative stage. The result of the lesson.-4.5 min

1) Verification of independent work with self-assessment. If all are completed test tasks- score "4", if the students managed to complete the task - "5"

Given: λ = 600 m, s = 3*108 m/s
Solution: ν \u003d c / λ \u003d 3 * 10^8 \ 600 \u003d 0.005 * 10^8 \u003d 0.5 * 10^6 Hz == 5 * 10^5 Hz

Answer: 500,000 Hz = 500 kHz = 0.5 MHz

2) Summing up and assessment and self-assessment of students.

What is an electromagnetic field?

What is an electromagnetic wave?

What do you now know about electromagnetic waves?

What is the significance of the studied material in your life?

What did you like the most about the lesson?

5. Homework-0.5 min P. 52.53 exercise. 43, ex. 44(1)

The history of the invention of the microwave-Internet.

Physics teacher MBOU secondary school №42, Belgorod

Kokorina Alexandra Vladimirovna

Class: 9

Thing: Physics.

the date of the:

Topic:“Electromagnetic field (EMF)”.

A type: combined lesson .

Lesson Objectives:

educational:

- to believe previously acquired knowledge;

- provide perception, comprehension, primary memorization of the concept of "electromagnetic field", the relationship of electric and magnetic fields;

- organize the activities of students to reproduce the studied information;

educational:

- education of labor motives, conscientious attitude to work;

- education of motives for learning, a positive attitude to knowledge;

— showing the role of physical experiment and physical theory in the study of physical phenomena.

developing:

- development of skills to creatively approach the solution of a wide variety of problems;

- development of skills to act independently;

Means of education:

- board and chalk;

Teaching methods:

- explanatory - illustrative .

Lesson structure (stages):

organizational moment (2 min);

updating of basic knowledge (10 min);

learning new material (17 min);

verification of understanding of the received information (8 min);

summarizing the lesson (2 min);

homework information (1 min).

During the classes

Teacher activity

Student activities

- greetings "Hello guys".

— fixing missing"Who is absent today?"

- greet the teacher "Hello"

- the attendant calls the absent

- physical dictation

“You have blank sheets on the tables, sign them and indicate the number of the option on which you are sitting. I will dictate questions to you one by one, first for the 1st, then for the 2nd option. Be careful "

Questions for the dictation:

1.1 What generates a magnetic field?

1.2 How can you visualize the magnetic field?

2.1 What is the nature of the IMF lines?

2.2 What is the nature of the WMD lines?

3.1 Magnetic induction: formula, units.

3.2 Lines of magnetic induction are ...

4.1 What can be determined by the right hand rule?

4.2 What can be determined by the left hand rule?

5.1 The phenomenon of EMP is ...

5.2 Alternating current is ...

“Now transfer your work to the first desks. Who didn't get the job done?"(sort out the issues that caused difficulties)

- sign works

- answer questions

Answers:

1.1 moving charges

1.2 magnetic lines

2.1 curved, their density varies

2.2 parallel to each other, located with the same frequency

3.1 B \u003d F / (I l), T

3.2 lines, tangents to which at each point of the field coincide with the direction of the magnetic induction vector

5.1 when changing the m.p., penetrating the circuit of a closed conductor, a current appears in the conductor

5.2 current, periodically changing in time in magnitude and direction

- conversation with the class:

“The topic of our lesson is written on the blackboard. And who will tell me in what year and by whom the EMP phenomenon was discovered?”

“What is it?”

“Under what conditions does current flow in a conductor?

“This means that we can conclude that the variable m.p., penetrating the closed circuit of the conductor, creates an e.p. in it, under the influence of which an induction current arises.

- explanation of new material:

“Based on this conclusion, James Clerk Maxwell in 1865 created a complex theory of EMF. We will consider only its main provisions. Write it down."

The main provisions of the theory:

3. These mutually generating variables e.p. and m.p. form an EMF.

5. (next lesson)

“A constant m.p. is created around charges moving at a constant speed. But if the charges move with acceleration, then the m.p. changes periodically.

Variable e.p. creates a variable m.p. in space, which in turn generates a variable e.p. etc."

Variable e.p. – vortex.

- answer the teacher's questions orally

“Michael Faraday, in 1831"

“when the mp changes, penetrating the loop of a closed conductor, a current arises in the conductor”

“ if it contains e.p.”

- write down in a notebook what the teacher dictates

“Now draw a table in your notebooks as if on a blackboard. Let's fill it together"

field

param.

comparisons

vortex	electrostatic
character	changes periodically over time	does not change over time
a source	fast moving charges	stationary charges
lines of force	closed	start with “+”; ends with “-”

- draw a table and fill it out with the teacher

- generalization and systematization:

“So, what important concept did you learn in class today? That's right, with the concept of EMF. What can you say about him?"

- reflection: “Who has difficulty understanding the material?”

Evaluation of the behavior and performance of individual students in the lesson.

- answer questions

- information about homework

“§ 51 , to prepare for control work. The lesson is over. Goodbye".

- write down homework

- say goodbye to the teacher: "Goodbye".

Students should have in their notebooks:

Topic: “Electromagnetic field (EMF)”.

1856 - J. Cl. Maxwell created the theory of EMF.

The main provisions of the theory:

1. Any change over time m.p. leads to the appearance of a variable e.p.

2. Any change with time in e.p. leads to the appearance of a variable m.p.

3. These mutually generating variables e.p. and m.p. form EMF.

4. EMF source - rapidly moving charges.

Variable e.p. – vortex.

comparisons

vortex	electrostatic
character	changes periodically over time	does not change over time
a source	fast moving charges	stationary charges
lines of force	closed	start with “+”; ends with “-”

"Electromagnetic waves".

Lesson Objectives:

Training:

to acquaint students with the features of the propagation of electromagnetic waves;
consider the stages of creation of the electromagnetic field theory and experimental confirmation this theory;

Educational: to acquaint students with interesting episodes of the biography of G. Hertz, M. Faraday, Maxwell D.K., Oersted H.K., A.S. Popova;

Developing: promote interest in the subject.

Demonstrations : slides, video.

DURING THE CLASSES

Today we will get acquainted with the features of the propagation of electromagnetic waves, note the stages in the creation of the theory of the electromagnetic field and the experimental confirmation of this theory, and dwell on some biographical data.

Repetition.

To achieve the objectives of the lesson, we need to repeat some questions:

What is a wave, in particular a mechanical wave? (Propagation of vibrations of particles of matter in space)

What quantities characterize a wave? (wavelength, wave speed, oscillation period and oscillation frequency)

Which mathematical connection between wavelength and period? (wavelength is equal to the product of the wave speed and the oscillation period)

Learning new material.

An electromagnetic wave is in many ways similar to a mechanical wave, but there are differences. The main difference is that this wave does not need a medium to propagate. An electromagnetic wave is the result of the propagation of an alternating electric field and an alternating magnetic field in space, i.e. electromagnetic field.

The electromagnetic field is created by rapidly moving charged particles. Its presence is relative. This is a special kind of matter, is a combination of variable electric and magnetic fields.

An electromagnetic wave is the propagation of an electromagnetic field in space.

Consider a graph of the propagation of an electromagnetic wave.

The scheme of propagation of an electromagnetic wave is shown in the figure. It must be remembered that the vectors of the electric field strength, magnetic induction and wave propagation velocity are mutually perpendicular.

Stages of creation of the electromagnetic wave theory and its practical confirmation.

Hans Christian Oersted (1820) Danish physicist, permanent secretary of the Royal Danish Society (since 1815).

Since 1806 - professor of this university, since 1829 at the same time director of the Copenhagen polytechnic school. Oersted's works are devoted to electricity, acoustics, molecular physics.

In 1820, he discovered the effect of electric current on a magnetic needle, which led to the emergence new area physics - electromagnetism. The idea of the relationship between various natural phenomena is characteristic of Oersted's scientific work; in particular, he was one of the first to suggest that light is an electromagnetic phenomenon. In 1822-1823, independently of J. Fourier, he rediscovered the thermoelectric effect and built the first thermoelement. Experimentally studied the compressibility and elasticity of liquids and gases, invented the piezometer (1822). Conducted research on acoustics, in particular, tried to detect the occurrence of electrical phenomena due to sound. Investigated deviations from the Boyle-Mariotte law.

Oersted was a brilliant lecturer and popularizer, organized the Society for the Propagation of Natural Science in 1824, created the first physics laboratory in Denmark, and contributed to the improvement of teaching physics in educational institutions country.

Oersted is an honorary member of many academies of sciences, in particular the St. Petersburg Academy of Sciences (1830).

Michael Faraday (1831)

The brilliant scientist Michael Faraday was self-taught. At school I received only primary education and then into force life problems worked and simultaneously studied popular scientific literature on physics and chemistry. Later, Faraday became a laboratory assistant with a well-known chemist at that time, then he surpassed his teacher and did a lot of important things for the development of such sciences as physics and chemistry. In 1821, Michael Faraday learned of Oersted's discovery that an electric field creates a magnetic field. After pondering this phenomenon, Faraday set out to create an electric field from a magnetic field, and as a constant reminder, he carried a magnet in his pocket. Ten years later, he made his motto a reality. Turned magnetism into electricity: a magnetic field creates - an electric current

The theoretical scientist deduced the equations that bear his name. These equations said that the variables magnetic and electric field create each other. It follows from these equations that an alternating magnetic field creates a vortex electric field, and it creates an alternating magnetic field. In addition, there was a constant in his equations - this is the speed of light in a vacuum. Those. it followed from this theory that an electromagnetic wave propagates in space at the speed of light in a vacuum. A truly brilliant work was appreciated by many scientists of that time, and A. Einstein said that Maxwell's theory was the most fascinating during his teachings.

Heinrich Hertz (1887)

Heinrich Hertz was born a sickly child, but became a very quick-witted student. He liked all the subjects he studied. The future scientist loved to write poetry, work on a lathe. After graduating from high school, Hertz entered higher technical school, but did not want to be a narrow specialist and entered Berlin University to become a scientist. After entering the university, Heinrich Hertz strived to study in a physical laboratory, but for this it was necessary to solve competitive problems. And he took up the solution of the following problem: does the electric current have kinetic energy? This work was designed for 9 months, but the future scientist solved it in three months. True, the negative result is incorrect from the modern point of view. The measurement accuracy had to be increased thousands of times, which was not possible at that time.

While still a student, Hertz defended his doctoral dissertation "excellent" and received the title of doctor. He was 22 years old. The scientist successfully engaged in theoretical research. Studying Maxwell's theory, he showed high experimental skills, created a device, which today is called an antenna, and with the help of transmitting and receiving antennas, created and received an electromagnetic wave and studied all the properties of these waves. He realized that the speed of propagation of these waves is finite and equal to the speed of propagation of light in a vacuum. After studying the properties of electromagnetic waves, he proved that they are similar to the properties of light. Unfortunately, this robot finally undermined the health of the scientist. First, the eyes failed, then the ears, teeth and nose hurt. He soon died.

Heinrich Hertz completed the enormous work begun by Faraday. Maxwell transformed Faraday's representations into mathematical formulas, and Hertz transformed mathematical images into visible and audible electromagnetic waves. Listening to the radio, watching television, we must remember this man. It is no accident that the unit of oscillation frequency is named after Hertz, and it is not at all accidental that the first words transmitted by the Russian physicist A.S. Popov using wireless communication, were "Heinrich Hertz", encrypted in Morse code.

Popov Alexander Sergeevich (1895)

Popov improved the receiving and transmitting antenna and at first communication was made at a distance of 250 m, then at 600 m. And in 1899, the scientist established radio communication at a distance of 20 km, and in 1901 - at 150 km. In 1900, radio communications helped carry out rescue work in the Gulf of Finland. In 1901, the Italian engineer G. Marconi made radio communications across the Atlantic Ocean.

Let's watch a video clip, where some properties of an electromagnetic wave are considered. After watching, we will answer questions.

Why does a light bulb in a receiving antenna change its intensity when a metal rod is introduced?

Why does this not happen when replacing a metal rod with a glass one?

Consolidation.

Answer the questions:

What is an electromagnetic wave?

Who created the electromagnetic wave theory?

Who studied the properties of electromagnetic waves?

Complete the answer table in your notebook, marking the question number.

How does wavelength depend on frequency?

(Answer: Inversely proportional)

What happens to the wavelength if the particle oscillation period is doubled?

(Answer: Will increase by 2 times)

How will the oscillation frequency of the radiation change when the wave passes into a denser medium?

(Answer: Will not change)

What causes electromagnetic waves to be emitted?

(Answer: Charged particles moving with acceleration)

Where are electromagnetic waves used?

(Answer: cell phone, microwave oven, TV, radio broadcast, etc.)

(Answers to questions)

Homework.

It is necessary to prepare reports on various types of electromagnetic radiation, listing their features and talk about their application in human life. The message should be five minutes long.

Types of electromagnetic waves:
Audio frequency waves
radio waves
microwave radiation
Infrared radiation
visible light
Ultraviolet radiation
x-ray radiation
Gamma radiation

Summarizing.

Literature.

Kasyanov V.A. Physics grade 11. - M.: Bustard, 2007
Rymkevich A.P. Collection of problems in physics. - M.: Enlightenment, 2004.
Maron A.E., Maron E.A. Physics grade 11. Didactic materials. - M.: Bustard, 2004.
Tomilin A.N. The world of electricity. - M.: Bustard, 2004.
Encyclopedia for children. Physics. - M.: Avanta +, 2002.
Yu. A. Khramov Physics. Biographical guide, - M., 1983

Class: 11

Lesson Objectives:

to acquaint students with the features of the propagation of electromagnetic waves;
consider the stages of creation of the electromagnetic field theory and experimental confirmation of this theory;

Educational: to acquaint students with interesting episodes from the biography of G. Hertz, M. Faraday, Maxwell D.K., Oersted H.K., A.S. Popova;

Developing: to promote the development of interest in the subject.

Demonstrations: slides, video.

DURING THE CLASSES

Org. Moment.

Annex 1. (SLIDE #1). Today we will get acquainted with the features of the propagation of electromagnetic waves, note the stages in the creation of the theory of the electromagnetic field and the experimental confirmation of this theory, and dwell on some biographical data.

Repetition.

To achieve the objectives of the lesson, we need to repeat some questions:

What is a wave, in particular a mechanical wave? (Propagation of vibrations of particles of matter in space)

What quantities characterize a wave? (wavelength, wave speed, oscillation period and oscillation frequency)

What is the mathematical relationship between wavelength and period of oscillation? (wavelength is equal to the product of the wave speed and the oscillation period)

(SLIDE #2)

Learning new material.

An electromagnetic wave is in many ways similar to a mechanical wave, but there are differences. The main difference is that this wave does not need a medium to propagate. An electromagnetic wave is the result of the propagation of an alternating electric field and alternating magnetic fields in space, i.e. electromagnetic field.

The electromagnetic field is created by rapidly moving charged particles. Its presence is relative. This is a special kind of matter, is a combination of variable electric and magnetic fields.

An electromagnetic wave is the propagation of an electromagnetic field in space.

Consider a graph of the propagation of an electromagnetic wave.

(SLIDE #3)

Stages of creation of the electromagnetic wave theory and its practical confirmation.

Hans Christian Oersted (1820) (SLIDE #4) Danish physicist, indispensable secretary of the Royal Danish Society (since 1815).

Since 1806 he was a professor at this university, since 1829 he was simultaneously director of the Copenhagen Polytechnic School. Oersted's works are devoted to electricity, acoustics, molecular physics.

(SLIDE #4). In 1820, he discovered the effect of electric current on a magnetic needle, which led to the emergence of a new field of physics - electromagnetism. The idea of the relationship between various natural phenomena is characteristic of Oersted's scientific work; in particular, he was one of the first to suggest that light is an electromagnetic phenomenon. In 1822-1823, independently of J. Fourier, he rediscovered the thermoelectric effect and built the first thermoelement. Experimentally studied the compressibility and elasticity of liquids and gases, invented the piezometer (1822). He conducted research on acoustics, in particular, he tried to detect the occurrence of electrical phenomena due to sound. Investigated deviations from the Boyle-Mariotte law.

Oersted was a brilliant lecturer and popularizer, organized the Society for the Propagation of Natural Science in 1824, created the first physics laboratory in Denmark, and contributed to improving the teaching of physics in the country's educational institutions.

Oersted is an honorary member of many academies of sciences, in particular the St. Petersburg Academy of Sciences (1830).

Michael Faraday (1831)

(SLIDE #5)

The brilliant scientist Michael Faraday was self-taught. At school he received only primary education, and then, due to life's problems, he worked and simultaneously studied popular science literature on physics and chemistry. Later, Faraday became a laboratory assistant with a well-known chemist at that time, then he surpassed his teacher and did a lot of important things for the development of such sciences as physics and chemistry. In 1821, Michael Faraday learned of Oersted's discovery that an electric field creates a magnetic field. After pondering this phenomenon, Faraday set out to create an electric field from a magnetic field, and as a constant reminder, he carried a magnet in his pocket. Ten years later, he made his motto a reality. Turned magnetism into electricity: ~ magnetic field creates ~ electric current

(SLIDE #6) The theoretical scientist deduced the equations that bear his name. These equations said that alternating magnetic and electric fields create each other. It follows from these equations that an alternating magnetic field creates a vortex electric field, and it creates an alternating magnetic field. In addition, there was a constant in his equations - this is the speed of light in a vacuum. Those. it followed from this theory that an electromagnetic wave propagates in space at the speed of light in a vacuum. A truly brilliant work was appreciated by many scientists of that time, and A. Einstein said that Maxwell's theory was the most fascinating during his teachings.

Heinrich Hertz (1887)

(SLIDE number 7). Heinrich Hertz was born a sickly child, but became a very quick-witted student. He liked all the subjects he studied. The future scientist loved to write poetry, work on a lathe. After graduating from the gymnasium, Hertz entered a higher technical school, but did not want to be a narrow specialist and entered the University of Berlin to become a scientist. After entering the university, Heinrich Hertz strived to study in a physical laboratory, but for this it was necessary to solve competitive problems. And he took up the solution of the following problem: does the electric current have kinetic energy? This work was designed for 9 months, but the future scientist solved it in three months. True, the negative result is incorrect from the modern point of view. The measurement accuracy had to be increased thousands of times, which was not possible at that time.

Heinrich Hertz completed the enormous work begun by Faraday. Maxwell transformed Faraday's ideas into mathematical formulas, and Hertz transformed mathematical images into visible and audible electromagnetic waves. Listening to the radio, watching television, we must remember this man. It is no accident that the unit of oscillation frequency is named after Hertz, and it is not at all accidental that the first words transmitted by the Russian physicist A.S. Popov using wireless communication, were "Heinrich Hertz", encrypted in Morse code.

Popov Alexander Sergeevich (1895)

Popov improved the receiving and transmitting antenna and at first communication was carried out at a distance

(SLIDE #8) 250 m, then 600 m. And in 1899, the scientist established radio communication at a distance of 20 km, and in 1901 - at 150 km. In 1900, radio communications helped carry out rescue work in the Gulf of Finland. In 1901, the Italian engineer G. Marconi made radio communications across the Atlantic Ocean. (Slide number 9). Let's watch a video clip, where some properties of an electromagnetic wave are considered. After watching, we will answer questions.

Why does a light bulb in a receiving antenna change its intensity when a metal rod is introduced?

Why does this not happen when replacing a metal rod with a glass one?

Consolidation.

Answer the questions:

(SLIDE #10)

What is an electromagnetic wave?

Who created the electromagnetic wave theory?

Who studied the properties of electromagnetic waves?

Complete the answer table in your notebook, marking the question number.

(SLIDE #11)

How does wavelength depend on frequency?

(Answer: Inversely proportional)

What happens to the wavelength if the particle oscillation period is doubled?

(Answer: Will increase by 2 times)

How will the oscillation frequency of the radiation change when the wave passes into a denser medium?

(Answer: Will not change)

What causes electromagnetic waves to be emitted?

(Answer: Charged particles moving with acceleration)

Where are electromagnetic waves used?

(Answer: cell phone, microwave oven, TV, radio broadcast, etc.)

(Answers to questions)

Let's solve the problem.

The Kemerovo television center transmits two carrier waves: an image carrier wave with a radiation frequency of 93.4 kHz and a sound carrier wave with a frequency of 94.4 kHz. Determine the wavelengths corresponding to the given radiation frequencies.

(SLIDE #12)

Homework.

(SLIDE #13) It is necessary to prepare reports on various types of electromagnetic radiation, listing their features and talk about their application in human life. The message should be five minutes long.

Types of electromagnetic waves:
Audio frequency waves
radio waves
microwave radiation
Infrared radiation
visible light
Ultraviolet radiation
x-ray radiation
Gamma radiation

Summarizing.

(SLIDE #14) Thank you for your attention and for your work!

Literature.

Kasyanov V.A. Physics grade 11. - M.: Bustard, 2007
Rymkevich A.P. Collection of problems in physics. - M.: Enlightenment, 2004.
Maron A.E., Maron E.A. Physics grade 11. Didactic materials. - M.: Bustard, 2004.
Tomilin A.N. The world of electricity. - M.: Bustard, 2004.
Encyclopedia for children. Physics. - M.: Avanta +, 2002.
Yu. A. Khramov Physics. Biographical guide, - M., 1983.