Mathematics and the hidden world of electromagnetic phenomena. Electromagnetic field Electromagnetic phenomena material on physics

Organization of research activities of students when studying the topic: “Electromagnetic phenomena” in physics in the eighth grade of a basic school in the light of the requirements of the Federal State Educational Standard for the results of mastering OOP

Rapid accumulation of knowledge acquired

with too little independent participation, they are not very fruitful.

Learning can also produce only leaves without producing fruit.

Lichtenberg

The Federal State Educational Standard for basic general education was approved by order of the Ministry of Education and Science of the Russian Federation dated December 17, 2010 No. 1897.

The fundamental difference between the second generation of Federal State Educational Standards is the focus on results, which involves the development of the individual based on the development of universal methods of activity.

Requirements for the results of mastering the basic educational program (BEP)

(personal, meta-subject, subject)

Personal – education of civic identity, readiness for self-education, formation of a holistic worldview, communicative competence, tolerance, mastery of social norms, rules of safe behavior, etc.

• Meta-subject - determine learning goals, plan ways to achieve them, evaluate the correctness of completing a learning task, master the basics of self-control, semantic reading, ICT competencies, etc.
• Subject - goals-results in subject areas and subjects (experience of activities specific to a given subject area, a system of fundamental elements of scientific knowledge)

Although the mandatory introduction of the Federal State Educational Standard for primary schools has not yet arrived, it is necessary today to restructure our work in such a way as to create conditions for the formation in students of:

• Universal learning activities
• ICT competencies
• Fundamentals of educational, research and project activities
• Basics of semantic reading and working with text

Universal learning activities are a system of student actions that ensures the ability to independently acquire new knowledge and skills, including the organization of educational activities.

The competency-based approach of the Federal State Educational Standard puts emphasis on the activity-based content of education. In this case, the main content of training is actions, operations, correlating not so much with the object of effort, but with the problem that needs to be resolved. In curricula, the activity-based content of education is reflected in the emphasis on methods of activity, skills and abilities, which need to be formed, on experience, which must be accumulated and comprehended by students, and on educational achievements which students must demonstrate.

The implementation of a competency-based approach is impossible without acquiring in-depth knowledge, since the most important feature of a competency-based approach is the student’s ability to self-learn in the future. The competency-based approach does not deny, but changes the role of knowledge. Knowledge is completely subordinate to skills. The content of training includes only that knowledge that is necessary for the formation of skills. All other knowledge is considered as reference; it is stored in reference books, encyclopedias, the Internet, etc., and not in the minds of students. At the same time, the student must, if necessary, be able to quickly and accurately use all these sources of information to resolve certain problems.

Thus, a competency standard is a standard of educational outcomes.

Competence is a person’s readiness to mobilize knowledge, skills and external resources for effective activity in a specific life situation.

I offer as a concrete example an attempt to implement a competency-based approach to teaching, i.e. students’ mastery of the basics of educational and research activities based on a real subject experiment, the organization of educational and research activities when studying the topic: “Electromagnetic phenomena” in physics in the eighth grade of a basic school. The organization of this educational and research activity of students was supposed to take into account the following principles:

• Creating internal motivation for the learning process based on arousing interest in the subject being studied
• — Activity approach based on the activation of individual cognitive independence
• — Problem-based learning
• Principle of learning success
• The ability to determine the volume of content and level of complexity of subject material by the student himself

Seven hours are allocated to study this topic in the eighth grade of basic school. Provision is made for demonstration and frontal experiments; performing one laboratory work: “Assembling an electromagnet and testing its action.”

The material on the topic “Electromagnetic Phenomena,” in my opinion, makes it possible not only to conduct various experiments, but to organize students’ research activities based on the use of experimental tasks in all lessons on this topic.

Organizing such activities is a rather labor-intensive process, but far from in vain. After all, it is known that skillfully conducting an experiment is the pinnacle of the study of physical phenomena, since it requires deep theoretical knowledge, skills in proper handling of instruments, the ability to construct graphs and competent calculations, the ability to evaluate the error of experience, the ability to analyze and draw conclusions.

You can learn all this only when you take direct part in practical activities. Therefore, the more often students turn to experimental tasks, the higher the quality of their knowledge will be, since familiarization with research activities and the opportunity to do something with their own hands also develops interest in the subject and helps to better assimilate it. Thus, physics lessons create a real opportunity to develop universal skills and abilities that students can apply in other subjects and in extracurricular, life situations.

The experimental tasks offered when studying this topic in the basic eighth grade are not difficult. They are not based on establishing quantitative patterns and require only qualitative explanation. But this in no way detracts from their merits. Completing such tasks requires students to be more independent, develops the ability to analyze their work and draw conclusions, which is still a certain difficulty for eighth-graders. And, of course, completing such tasks develops the skill of working with instruments and maintains students’ interest in studying electromagnetic phenomena. The proposed experimental tasks are not something new; they are well known. But at the same time, the nature of their use gives them a certain novelty. Also, in addition to performing the direct experimental task, students are required to provide an independent theoretical explanation of it based on studying the text of the textbook. It is proposed to review and submit, if desired, additional material on this topic from other sources. At each lesson, students have the opportunity to demonstrate their acquired knowledge. The development of communication skills is facilitated by the work of students in pairs and groups. Of course, successful study of this topic through educational and research activities should be preceded by systematic reference to various classroom and home experimental tasks.

Lesson-by-lesson distribution of topic material "Electromagnetic phenomena"

1. Permanent magnet and conductor with current.

2. Magnetic field on paper.

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

4. Ubiquitous electromagnets.

5. Conductor with current in a magnetic field.

6. Coil with current in a magnetic field.

7. Electromagnetic world.

Experimental and methodological support of the topic.

1. Laboratory equipment: permanent magnets, compass, small metal bodies, current source, rheostat, ammeter, connecting wires, key, compass, iron filings, thick sheet of paper, coil of wire, solenoid, metal core and paper clip, dynamometer, electric motor model.

2. Handouts (progress of experimental research)

3. Computer support for lessons. Ready-made products used: “Educational complex “Preparation for the Unified State Exam grades 10-11”, “Physics in pictures”.

Students' teaching and learning complex

• A.V. Peryshkin. Physics 8. Bustard. M. 2002
• G.N. Stepanova, A.P. Stepanov. Collection of questions and problems in physics. Basic school. "Valerie SPD" St. Petersburg. 2001

Lesson content

Lesson #1

Permanent magnet and current carrying conductor.

The purpose of the lesson.

Introduce the concept of magnetic field.

Lesson objectives:

• make sure that a magnetic field is formed around a permanent magnet and a current-carrying conductor;
• find out whether the magnetic field can be detected using the senses;
• whether the magnetic field has a direction, and whether its effect can be strengthened or weakened.

During the classes.

Setting the goal of the lesson.

Electrical phenomena have already been discussed in sufficient detail. Let’s begin to study magnetic phenomena and try to make sure that these phenomena are interconnected and that it is no coincidence that the new topic is called “Electromagnetic phenomena.” As we study this topic, we will keep a research diary. Let's divide it in half. In one half the results of experiments will be presented, in the other - their theoretical explanations. At the last lesson we will hold a diary competition.

You have already assembled electrical circuits more than once and become familiar with the peculiarities of the flow of electric current in them, and have used permanent magnets more than once in your life. Let's find out if a permanent magnet and a current-carrying conductor have anything in common?

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

Experimental Study No. 1

Permanent magnet

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

Equipment: permanent magnet, compass, small metal bodies.

Progress of the study.

1. Apply a permanent magnet in turn to a pencil, an eraser and to different metal bodies.

Watch what happens.

2. Achieve the maximum possible attraction of bodies with a magnet.

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

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

Observe the behavior of the compass needle.

4. Based on the results of your observations, formulate the main properties of a permanent magnet.

Current carrying conductor

Purpose of the study: find out what unites a permanent magnet and a conductor with current.

Progress of the study.

1. Using your senses, explore the space around the permanent magnet and around some body (ruler, pencil).

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

Draw conclusions about the results of your experience.

3. Draw a diagram of an electrical circuit consisting of a current source, rheostat, ammeter, switch and connecting wires, connecting all elements in series:

• Place any connecting wire above the compass needle parallel to its needle at a short distance without closing the circuit (the compass lies on the table). Does this cause the compass needle to deflect?
• Close the circuit and watch what happens to the compass needle.
• Remove the compass, open the circuit. Try to determine using your senses whether anything changes when the circuit is closed.

4.Draw a conclusion based on the results of the study.

(A permanent magnet and a current-carrying conductor interact with a magnetic needle)

Working with the textbook. (computer model of Oersted's experiment)

• Who and when first performed an experiment with a conductor with current and a magnetic needle?
• What acted in our study on the magnetic needle, deflecting it?
• How can we now answer the question: what unites a permanent magnet and a conductor with current?

Is it possible to detect a magnetic field using our senses?

How can it be detected?

Lesson summary.

Invisible object detected. Which? Where? With using what? What did you know about him?

Homework

Using the material from paragraphs 56 and 59 of the textbook, give a theoretical explanation of the results of your experiments.

Lesson #2

Magnetic field on paper.

The purpose of the lesson .

Introduce a graphical method of depicting magnetic fields.

Lesson objectives.

• Find out whether the magnetic field has a direction and whether its effect can be strengthened or weakened.
• Introduce the concept of magnetic lines.
• Find out what role iron filings play
• Consider the picture of the magnetic lines of a permanent magnet and a current-carrying conductor.

During the classes

Setting the goal of the lesson.

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

Posting diaries. Comparison and clarification of conclusions. Making additions. Discussion of Ampère's conjecture. The main conclusion: a magnetic field is formed around moving electric charges.

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

Let's return to the magnetic field. How can it be discovered? Is this knowledge enough to depict the magnetic field on paper? What else do you need to know about him?

Can it be weakened or strengthened?

Does it have a direction?

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

Experimental Study No. 3

A magnetic field

Purpose of the study: find out whether the magnetic field has a direction and whether its effect can be strengthened or weakened.

Equipment: permanent magnet, current source, rheostat, ammeter, connecting wires, key, compass.

Progress of the study

1.Apply the compass to a permanent magnet from different directions.

Does the compass needle behave the same way?

2. Place the compass needle near the edges of the magnet and in the middle of it. Observe the behavior of the arrow in each case.

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

4. Do Oersted’s experiment several times, changing the direction and strength of the current in the conductor. Observe the behavior of the compass needle in each case.

5. Write down the conclusions from the research.

So, a magnetic field can act stronger or weaker, and in different directions. Therefore, it can be weak or strong and has a direction. And all this must be taken into account when depicting it on paper.

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

Physicists did just that, and took the direction of the magnetic field as the direction coinciding with the direction indicated by the north pole of the magnetic needle. They also agreed to depict the magnetic field using lines along which the axes of small magnetic arrows are located. Let's call them magnetic lines. The direction of the magnetic lines at each point in the field coincides with the direction indicated by the north pole of the magnetic needle. Ordinary iron filings helped determine the location of magnetic lines. Why? Let's find out!

Experimental Study No. 4

Iron filings

Purpose of the study: find out what role iron filings playwhen studying the magnetic field.

Equipment: permanent magnet, iron filings, thick sheet of paper.

Progress of the study

1. Place a piece of paper on a pencil. Sprinkle iron filings onto the paper. Gently tap the piece of paper. Watch what happens.
2. Repeat your steps using a permanent magnet instead of a pencil.
3. Carefully turn the magnet over under the sheet of paper without disturbing the sawdust.
4. Compare the density of the iron filings.
5. Draw a conclusion about the behavior of iron filings in a magnetic field.
   Working with the textbook.
   What do the arrangement of magnetic lines of a permanent magnet and a current-carrying conductor have in common?
   How can you change the direction of the magnetic lines of a current-carrying conductor and permanent magnets?
   Demonstration and discussion of the video: magnetic lines of a direct current-carrying conductor.
   Continuation of research No. 4.
6. Get a picture of magnetic lines between like poles of magnets.
7. Point the magnets with opposite poles towards each other.
8. Watch what happens.
9. Explain your observations.

Lesson summary.

How are magnetic fields represented graphically? Are the rules by which patterns of various magnetic fields are obtained conventional or based on experience (demonstration of computer models)?

Homework

• Using the material from paragraphs 56 and 57 of the textbook, make the necessary additions in your opinion to the diaries on the content of the lesson.
• From the collection of tasks, complete No. 1849 and No. 1880.

Lesson #3

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

The purpose of the lesson:

explore and compare the magnetic field of a coil with current

with the magnetic field of a permanent magnet.

Lesson objectives:

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

What does the pattern of the magnetic field of the solenoid depend on?

During the classes.

Magnetic fields can be represented graphically. How?

Let us now try to predict its properties using the known picture of the magnetic field. Let's check our conclusions empirically. To do this, compare the picture of the magnetic field of a current-carrying coil (solenoid) with the picture of the magnetic field of a strip magnet.

Demonstration of a computer model (disc: “Physics in Pictures”):

image of the magnetic fields of a permanent magnet and solenoid.

Model analysis.

Comparing the density of magnetic lines in both bodies, we can identify ... (poles)

Both the permanent magnet and the solenoid also have a region where the magnetic field is ... (uniform)

So, in this case, the patterns of magnetic fields of a strip magnet and a coil with current... (are the same). Will their properties be the same?

Will the patterns of these fields always be similar?

Let's conduct an experimental study.

Experimental Study No. 5

Solenoid

Purpose of the study:

• check whether the properties of the magnetic fields of the strip magnet and the solenoid are the same;
• find out how you can change the properties of the magnetic field of the solenoid.

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

Progress of the study

1. Experiments with wire coil:

• Using the available equipment, create a magnetic field at the wire coil (use all devices that can be included in the electrical circuit).
• Make sure it's there. Determine its direction.
• Determine whether the coil with current has poles.
• Draw a conclusion about the nature of the magnetic field of a coil with current.
• Change the direction of the current in the coil.
• Find out whether its magnetic field has changed?

2.Experiments with solenoid:

• Repeat the experiments using a coil (solenoid) instead of a coil.

• Has the nature of the magnetic field changed?
• Using a rheostat, increase the magnetic field of the solenoid.
• Make sure it gets stronger.
• Insert the metal core into the solenoid.
• Determine how the nature of the magnetic field of the solenoid changed.

3.Draw a conclusion based on the results of the study in accordance with its purpose.

Lesson summary.

Return to the computer model.

So will the magnetic field patterns of a permanent magnet and a solenoid always be the same?

Explanation of the changing patterns of the magnetic lines of the solenoid on the slide.

Can we just as easily change the pattern of magnetic lines of a strip magnet?

Can permanent magnets also be called natural magnets? What about the solenoid? (artificial magnet). Such a magnet was created using electric current. Therefore, such magnets are also called electromagnets.

Homework:

• Find out who and when invented the first electromagnet, where electromagnets are used today, by finding information in the textbook or other sources (paragraph No. 58).
• Also suggest your ways of using electromagnets.
• Complete number 1895 from the problem book.

Lesson #4

Ubiquitous electromagnets.

Objective of the lesson: consider the use of electromagnets.

Lesson objectives:

• find out how you can control electromagnets
• analyze specific cases of using electromagnets
• determine the advantages of electromagnets over permanent magnets

During the classes

1. Setting the goal of the lesson.

While doing your homework, you probably became convinced that electromagnets have found very wide application. Let's find out why this became possible and use specific examples to determine the advantages of electromagnets.

Let's start by analyzing the homework problem. What was proposed to be investigated in this task? What research methods can you suggest? Let's now conduct a similar study.

Experimental Study No. 6

Electromagnets

Purpose of the study: find out how the force of interaction of an electromagnet with a metal paper clip depends on the current strength in its winding.

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

Progress of the study

1.Draw up a research plan.

2. Swipe it.

3.Draw a conclusion based on the results of your research in accordance with its purpose (analysis of the graphical representation of the research results is assumed).

Work in groups.

1. Report the results of your research.
2. Give examples of the use of electromagnets known to you.
3. Give your examples of the use of electromagnets.
4. Explain the actions of electromagnets discussed in task No. 9 of the textbook. (Accompanied by a demonstration or video.)
5. Explain the possibility of widespread use of electromagnets.

Lesson summary.

The lesson was called: “Ubiquitous electromagnets.” Did it live up to its name? Give reasons for your answer. Briefly write down your arguments.

Homework.

• Make sure your diary is in order.
• Complete exercise No. 28 of the textbook.
• From the collection of tasks, complete No. 1905 and No. 1907.

Lesson #5

Conductor with current in a magnetic field.

Purpose of the lesson: consider the effect of a magnetic field on a current-carrying conductor.

Lesson objectives:

• Find out what will happen to a current-carrying conductor if it is introduced into a magnetic field.
• Determine what determines the magnitude and direction of the Ampere force.
• Find out how you can make a coil with current turn in a magnetic field.

During the classes

Analysis and correction of homework.

Posting diaries and completed tasks.

Setting the goal of the lesson.

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

Let's conduct experiments.

Experimental Study No. 7

Conductor carrying current in a magnetic field

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

Equipment: current source, coil of wire, rheostat, ammeter, connecting wires, key, permanent arc magnet.

Progress of the study

1. Draw a diagram of an electrical circuit consisting of a current source, a rheostat, an ammeter, a coil of wire, a key and connecting wires, connecting all the elements in series.

• Assemble an electrical circuit according to this diagram.
• Place the coil on the permanent magnet.
• Complete the circuit. Observe what happens to the coil.
• Repeat the experiments, changing the position of the magnet.
• Repeat the experiments using two magnets placed together with like poles.
• Observe what changes happen.
• Repeat the experiments, changing the direction and strength of the current in the coil one by one.
• Draw a conclusion about what and how happens to a coil with current in a magnetic field.
• Try to make a current-carrying coil turn in a magnetic field.
• Explain how you achieved this.
• Share your observations and conclusions (show demonstrations with a straight conductor carrying current in a magnetic field).

Lesson summary.

• So a magnetic field can be detected not only by its effect on the magnetic needle, but also by its effect on ....? The magnitude and direction of the force acting on a current-carrying conductor in a magnetic field depends on...? The effect of a magnetic field on a current-carrying conductor placed in it is used in electric motors. In the next lesson we will learn more about their structure.

Homework.

• Using the material from paragraph 61, explain the course of the experiments depicted in Figures 113 and 114 of the textbook;
• give examples of the use of electric motors;
• Find out who and when invented the first electric motor suitable for practical use.
• Don't forget about your diaries!

Lesson #6

Coil with current in a magnetic field

Purpose of the lesson: Consider the structure and principle of operation of electric motors and electrical measuring instruments.

Lesson objectives:

• Find out how it is practically possible to rotate a conductor with current in a magnetic field.
• Consider the design of a technical electric motor.
• Determine the advantages of electric motors over thermal ones.
• Consider the design of electrical measuring instruments.

During the classes

Analyzing, adjusting homework and setting lesson goals.

We found out that a magnetic field acts on a current-carrying conductor placed in it. And as we have already seen, it can even turn it!

Give examples of the use of electric motors. Remember what their action leads to. What type of movement of a current-carrying conductor do you think is used in electric motors?

Let's find out how you can make a current-carrying conductor rotate in a magnetic field? And finally, we will get acquainted with the design of technical electric motors and other devices that use rotation

current-carrying conductor in a magnetic field.

Let us remember why the current-carrying coil rotated in a magnetic field. What needs to be done to make it not just turn, but also rotate?

Experimental Study No. 8

Purpose of the study: find out how technically the frame is rotated with current in a magnetic field.

Equipment: electric motor model.

1. Formulate the conditions under which a current-carrying frame will rotate in a magnetic field.

2. Consider the model of the electric motor (video demonstration).

3. Name the devices that allow a current-carrying frame to rotate in a magnetic field and explain how they operate.

Working with the textbook.

1.Fill out the table.

Main parts of the electric motor

Purpose

Device

2. Determine the advantages of electric motors over thermal ones.

3. Complete task No. 11 of the textbook.

Lesson summary.

Posting of completed tables. Analysis of the proposed tasks. We were convinced that the rotation of a current-carrying conductor in a magnetic field is quite widely used.

Determine what is common and what is different in the operation of electric motors and electrical measuring instruments.

Homework.

• From the collection of problems, complete No. 1920 and No. 1928.

• Prepare research diaries for review.
• Make a final collection of arguments that serve as evidence that the topic studied is not accidentally called: “Electromagnetic phenomena.”
• Using the textbook (paragraph No. 60) and additional sources, collect information about the Earth's magnetic field.

Lesson #7

Electromagnetic world.

Purpose of the lesson: summarize and systematize the material on the topic: “Electromagnetic phenomena”

Lesson objectives:

• Organize students' analytical activities.
• Check the degree to which students have mastered the topic material.

During the classes

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

·Complete tasks.

1. Experimenters prepare a demonstration of electromagnetic phenomena using the proposed equipment.

2. Theorists are preparing to express arguments based on the homework material.

3. Experts evaluate the research diaries of team members and select the best ones.

· Posting of completed tasks.

1.Teams take turns presenting their arguments, including demonstrating experimental evidence.

2. An exhibition of the best diaries will be organized.

· Test tasks.

1. A “pyramid” is played.

2. Testing is carried out.

"Pyramid"

It is necessary to guess the words, explaining their meaning, using only the material from the topic: “Electromagnetic phenomena.”

arrow magnet lines

Earth coil field

Oersted sawdust core

Electromagnet direction iron

Compass solenoid density

Nickel pole storm

Test

1.The magnetic needle always turns:

A) in the Earth’s magnetic field;

B) near a permanent magnet;

B) near a conductor carrying current

D) near the ebonite stick.

2. This happens because around these bodies the following is formed:

A) gravitational field;

B) magnetic field;

B) electric field;

D) biofield.

H. Since a magnetic field is formed around charged particles if they:

A) exist;

B) are at rest;

B) collide;

D) are moving.

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

A) change the direction of the magnetic lines in it;

B) increase the current in the circuit;

C) change the polarity of the current source connection;

D) change the direction of winding of the solenoid wire.

5. To strengthen the magnetic field of the solenoid it is necessary:

A) remove the core from it

B) reduce the total resistance of the circuit;

C) increase the number of turns;

D) make a winding of thinner wire.

6. An electromagnet can be used to

A) close the circuit at the right moment;

B) carry a heavy metal load;

C) remove the smallest metal bodies that have gotten into them from the eyes;

D) make a secret bolt on the door.

Screening test

Electromagnetic phenomena

10.1. The passage of current through a solid, liquid or gaseous conductor is always accompanied by the appearance magnetic field. Its lines of force are closed curves encircling the conductor.

10.2. Magnetic field line direction- in the direction where the northern end of the small magnetic needle, placed at the field point being studied, points. When the direction of current in a conductor changes, the direction of the power lines changes to the opposite.

10.3. Electromagnets- conductors twisted into spirals or coils, inside which there is a core of iron or steel. Electromagnets (also called inductors) are capable of storing and returning electrical energy to a circuit by converting it into magnetic field energy and vice versa.

10.4. permanent magnets- non-electrified bodies that are capable of attracting objects made of iron, steel and some other materials and retaining this property for a long time.

10.5. Magnet pole– the place on the surface of a magnet where the magnetic field is strongest. The field lines of a permanent magnet are closed. They leave its north pole and enter the south, closing inside the magnet.

10.6. The Earth, as well as some other celestial bodies, are permanent magnets, that is have a magnetic field.

10.7. A magnetic field acts on moving charged particles and, as a result, onto current-carrying conductors. The action of electrical measuring instruments and electric motors is based on this phenomenon.

10.8. Electric motors Regardless of their design, they have a rotating part (rotor) and a stationary part (stator). Depending on their purpose, they contain electromagnets or permanent magnets, as well as a collector - a device for regulating the flow of current at the right moments during each rotation of the rotor.

10.9. Electromagnetic induction– the phenomenon of the occurrence of current in a conductor moving in a magnetic field or in a stationary conductor located in a moving (changing) magnetic field.

10.10. The greatest use in everyday life and industry in European countries has been alternating induction current, changing its direction 100 times per second, that is, with a frequency of 50 Hz.

10.11. Electric transformer- a device used to convert alternating current of one voltage into current of another voltage. The operating principle of the transformer is based on the phenomenon of electromagnetic induction.

10.12. To transmit electricity over a distance use step-up transformers, high-voltage power lines and step-down transformers.

10.13. To drive powerful machines and installations they use motors operating on three-phase alternating current. Their advantages: simplicity of design, high reliability and power.

Electromagnetic phenomena. Tables and diagrams.

Formulas of electricity and magnetism. The study of the fundamentals of electrodynamics traditionally begins with an electric field in a vacuum. To calculate the force of interaction between two point charges and to calculate the strength of the electric field created by a point charge, you need to be able to apply Coulomb's law. To calculate the field strengths created by extended charges (charged thread, plane, etc.), Gauss's theorem is used. For a system of electric charges, it is necessary to apply the principle

When studying the topic "Direct Current" it is necessary to consider Ohm's and Joule-Lenz's laws in all forms. When studying "Magnetism" it is necessary to keep in mind that the magnetic field is generated by moving charges and acts on moving charges. Here we should pay attention to the Biot-Savart-Laplace law. Particular attention should be paid to the Lorentz force and consider the motion of a charged particle in a magnetic field.

Electrical and magnetic phenomena are connected by a special form of existence of matter - the electromagnetic field. The basis of the electromagnetic field theory is Maxwell's theory.

Table of basic formulas for electricity and magnetism

Physical laws, formulas, variables	Formulas for electricity and magnetism
Coulomb's Law: Where q 1 and q 2 - the magnitude of point charges,ԑ 1 - electric constant; ε is the permittivity of an isotropic medium (for vacuum ε = 1), r is the distance between the charges.
Electric field strength: where Ḟ is the force acting on the charge q 0 located at this point in the field.
Field strength at a distance r from the field source: 1) point charge 2) an infinitely long charged thread with linear charge density τ: 3) a uniformly charged infinite plane with surface charge density σ: 4) between two oppositely charged planes
Electric field potential: where W is the potential energy of the charge q 0 .
Potential of the field of a point charge at a distance r from the charge:
According to the principle of superposition of fields, the intensity:
Potential: where Ē i and ϕ i- tension and potential at a given point of the field, created by the i-th charge.
The work of the forces of the electric field to move the charge q from a point with a potentialϕ 1 to a point with potentialϕ 2:
Relationship between tension and potential 1) for a non-uniform field: 2) for a uniform field:
Electric capacity of a solitary conductor:
Capacitance of the capacitor:
Electrical capacity of a flat capacitor: where S is the area of ​​the plate (one) of the capacitor, d is the distance between the plates.
Energy of a charged capacitor:
Current strength:
Current Density: where S is the cross-sectional area of ​​the conductor.
Conductor resistance: l is the length of the conductor; S is the cross-sectional area.
Ohm's law 1) for a homogeneous section of the chain: 2) in differential form: 3) for a section of the circuit containing EMF: Where ε is the emf of the current source, R and r - external and internal resistance of the circuit; 4) for a closed circuit:
Joule-Lenz law 1) for a homogeneous section of a DC circuit: where Q is the amount of heat released in the current-carrying conductor, t - current passage time; 2) for a section of a circuit with a current varying over time:
Current power:
Relationship between magnetic induction and magnetic field strength: where B is the magnetic induction vector, μ √ magnetic permeability of an isotropic medium, (for vacuum μ = 1), µ 0 - magnetic constant, H - magnetic field strength.
Magnetic induction(magnetic field induction): 1) in the center of the circular current where R is the radius of the circular current, 2) fields of infinitely long forward current where r is the shortest distance to the conductor axis; 3) the field created by a section of conductor with current where ɑ 1 and ɑ 2 - angles between the conductor segment and the line connecting the ends of the segment and the field point; 4) fields of an infinitely long solenoid where n is the number of turns per unit length of the solenoid.

Greetings, dear readers. Nature hides many secrets. Man managed to find explanations for some mysteries, but not for others. Magnetic phenomena in nature occur on our earth and around us, and sometimes we simply do not notice them.

One of these phenomena can be seen by picking up a magnet and pointing it at a metal nail or pin. See how they are attracted to each other.

Many of us still remember experiments with this object, which has a magnetic field, from our school physics course.

I hope you remember what magnetic phenomena are? Of course, this is the ability to attract other metal objects to itself, having a magnetic field.

Consider magnetic iron ore, from which magnets are made. Each of you probably has such magnets on your refrigerator door.

You might be interested to know what other magnetic natural phenomena are there? From school physics lessons we know that fields can be magnetic and electromagnetic.

Let it be known to you that magnetic iron ore was known in living nature even before our era. At this time, a compass was created, which the Chinese emperor used during his numerous campaigns and just sea walks.

The word magnet is translated from Chinese as a loving stone. Amazing translation, isn't it?

Christopher Columbus, using a magnetic compass in his travels, noticed that geographic coordinates affect the deviation of the compass needle. Subsequently, this observation result led scientists to the conclusion that there are magnetic fields on earth.

The influence of the magnetic field in living and inanimate nature

The unique ability of migratory birds to accurately locate their habitats has always been of interest to scientists. The earth's magnetic field helps them lay unmistakably. And the migrations of many animals depend on this field of earth.

So not only birds, but also such animals as:

• Turtles
• Sea shellfish
• Salmon fish
• Salamanders
• and many other animals.

Scientists have found that in the body of living organisms there are special receptors, as well as magnetite particles, which help sense magnetic and electromagnetic fields.

But how exactly any living creature living in the wild finds the right landmark cannot be answered unequivocally by scientists.

Magnetic storms and their impact on humans

We already know about the magnetic fields of our earth. They protect us from the effects of charged microparticles that reach us from the Sun. A magnetic storm is nothing more than a sudden change in the electromagnetic field of the earth that protects us.

Haven’t you noticed how sometimes you have a sudden sharp pain shooting into the temple of your head and then a severe headache immediately appears? All these painful symptoms occurring in the human body indicate the presence of this natural phenomenon.

This magnetic phenomenon can last from an hour to 12 hours, or can be short-lived. And as doctors have noted, older people with cardiovascular diseases suffer more from this.

It has been noted that during a prolonged magnetic storm the number of heart attacks increases. There are a number of scientists who monitor the occurrence of magnetic storms.

So, my dear readers, sometimes it’s worth learning about their appearance and trying to prevent their terrible consequences if possible.

Magnetic anomalies in Russia

Throughout the vast territory of our earth there are various kinds of magnetic anomalies. Let's find out a little about them.

The famous scientist and astronomer P.B. Inokhodtsev, back in 1773, studied the geographical location of all cities in the central part of Russia. It was then that he discovered a strong anomaly in the area of ​​Kursk and Belgorod, where the compass needle was spinning feverishly. It was only in 1923 that the first well was drilled, which revealed metal ore.

Scientists even today cannot explain the huge accumulations of iron ore in the Kursk magnetic anomaly.

We know from geography textbooks that all iron ore is mined in mountainous areas. It is unknown how the iron ore deposits were formed on the plain.

Brazilian magnetic anomaly

Off the ocean coast of Brazil, at an altitude of more than 1000 kilometers, most of the instruments of aircraft flying over this place - airplanes and even satellites - stop their work.

Imagine an orange orange. Its peel protects the pulp, and the magnetic field of the earth with a protective layer of the atmosphere protects our planet from harmful influences from space. And the Brazilian anomaly is like a dent in this peel.

In addition, mysterious ones were observed more than once in this unusual place.

There are still many mysteries and secrets of our land to be revealed to scientists, my friends. I would like to wish you good health and that unfavorable magnetic phenomena will bypass you!

I hope you enjoyed my brief overview of magnetic phenomena in nature. Or maybe you have already observed them or felt their effect on yourself. Write about it in your comments, I will be interested to read about it. And that's all for today. Let me say goodbye to you and see you again.

I suggest you subscribe to blog updates. You can also rate the article according to the 10 system, marking it with a certain number of stars. Come visit me and bring your friends, because this site was created especially for you. I am sure that you will definitely find a lot of useful and interesting information here.

10) Characteristics of the chain section:

Current strength - , measured with an ammeter;

Voltage - , measured with a voltmeter;

Resistance - , measured with an ohmmeter.

11) Ohm's law for a chain section:.

12) Two types of conductor connection:

Sequential (see Fig. 4)

Rice. 4. Series connection of conductors

Parallel (see Fig. 5)

Rice. 5. Parallel connection of conductors

13) Current work: .

14) Current power: .

15) The amount of heat that is released when current passes through a conductor: .

16) Electric current in various environments:

In metals there is a directed movement of free electrons;

In liquids - the directed movement of free ions resulting from electrolytic dissociation. Law of Electrolysis:

In gases - the directed movement of free ions and electrons formed in

result ionization;

- in semiconductors - directed movement of free electrons and holes;

17) Magnets:

Electromagnets;

Permanent:

natural;

artificial.

18) Around any charged particle, and therefore around a conductor with current, there is a magnetic field.

19) A magnetic field- a special form of matter that exists around moving charged particles or bodies and acts with some force on other charged particles or bodies moving in this field.

20) Magnetic field lines- conditional lines along which the axes of small magnetic arrows are installed in the magnetic field:

The direction of the magnetic field lines coincides with the direction indicated by the north pole of the magnetic needle (see Fig. 6);

The direction of the magnetic field lines of a current-carrying conductor can be determined using right hand rules or gimlet rules(see Fig. 7);

Magnetic lines leave the north pole and enter the south pole;

Magnetic field lines are always closed.

21) A conductor with current in a magnetic field is affected by Ampere power. Its direction is determined according to the left hand rule(see Fig. 8).

Rice. 7. Right hand rule and gimlet rule

Rice. 8. Left hand rule

22) Phenomenon electromagnetic induction- the phenomenon of generation of an electric field in space by an alternating magnetic field.

In this lesson, we recalled various facts regarding electromagnetic phenomena studied earlier, and also discussed the general electromagnetic picture of the world.

The electric arc was first used outside the laboratory in 1845 at the Paris National Opera to reproduce the effect of the rising sun.

In Thailand, problems arose during the construction of power lines. The first concerned the fact that monkeys, imitating electricians, climb onto wires along supports and, entangling them, create a short circuit. Elephants posed a second problem, as they would tear supports out of the ground.

The Earth's magnetic field periodically changes its polarity, performing both secular fluctuations lasting 5-10 thousand years, and completely reorienting (the magnetic poles change places) 2-3 times over the course of a million years. This is evidenced by the “frozen” magnetic field in sedimentary and volcanic rocks of distant eras. However, the Earth's geomagnetic field does not undergo chaotic changes, but obeys a certain schedule.

Ancient archives contain records indicating that Emperor Nero, who suffered from rheumatism, was treated with electric baths. To do this, electric stingrays were placed in a wooden tub with water. While in such a bath, the emperor was exposed to electrical discharges and fields.

In the last century, an electric nanny was invented in Switzerland. The inventor proposed placing two insulated metal meshes under baby diapers, separated by a dry pad. These grids were connected to a low-voltage current source, as well as an electric bell. When the pad became wet, the circuit closed and the bell informed the mother that the diaper needed to be changed.

In those regions of Russia where there are severe frosts in winter, the problem of draining petroleum products from railway tanks arises, since the viscosity of petroleum products at low temperatures is too high. Scientists from Far Eastern institutes have developed a technology for electric induction heating of tanks (see Fig. 9), which can significantly reduce energy costs, since heating tanks with steam requires about 15 tons of fuel.

Rice. 9. Electric induction heating of tanks

For emergency situations when heating and water supply systems freeze, a hand-held electric induction tool has been developed that ensures rapid heating of pipelines and high work safety.

Even spent cartridges and cartridges retain the fingerprints of the person who placed them in the weapon. These fingerprints can be identified using a technique developed by specialists from the Saratov Law Institute. Having placed the cartridge case or cartridge in an electric field as an electrode, a thin metal film is sprayed onto it in a vacuum, and prints that can be identified become visible on it.

Problem 1

Which of the drawings correctly depicts the poles of magnets (see Fig. 10)?

Rice. 10. Illustration for the problem

Solution

Magnetic lines for a permanent magnet are lines that begin at the north magnetic pole and end at the south, outside the magnet itself. Inside the magnet, these lines close, but are already directed from the south pole to the north magnetic pole.

In the first picture, the poles are depicted incorrectly, since the magnetic lines are directed from the south pole to the north.

In the second picture, the poles are depicted incorrectly, since the magnetic lines are directed from the south pole to the north.

In the third figure, the poles are depicted correctly, since the magnetic lines are directed from the north pole to the south.

In the fourth picture, in all likelihood, two identical poles were meant.

Answer: in the third picture the poles are depicted correctly.

Try to answer this question yourself: at which of these points is the action of the magnet the strongest, and at which - the smallest (see Fig. 11)?

Rice. 11. Illustration for the problem

You can solve this problem by remembering how magnetic lines are distributed in space near a permanent magnet.

1. Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. / Ed. Orlova V.A., Roizena I.I. Physics 8. - M.: Mnemosyne.
2. Peryshkin A.V. Physics 8. - M.: Bustard, 2010.
3. Fadeeva A.A., Zasov A.V., Kiselev D.F. Physics 8. - M.: Enlightenment.

1. Class-fizika.narod.ru ().
2. Clck.ru ().
3. Clck.ru ().

Homework

1. What confirms the existence of the Earth's magnetic field?
2. Define magnetic lines. What are magnetic lines of direct current, coils with current?
3. What did the creation of the electromagnetic picture of the world give to science?
4. Ampere power. Left hand rule.
5. A voltage of 12 mV is applied to an iron conductor 10 m long and with a cross section of 2 mm2. What is the strength of the current flowing through the conductor?
6. Electric lamps with a resistance of 200 ohms and 400 ohms are connected in parallel and connected to a current source. How do the amounts of heat compare? Q 1 and Q 2 emitted by lamps at the same time?