Magnetic induction presentation. Magnetic induction

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Formulate a problem for each case of the interaction of a magnetic field with a current and solve it.

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В – magnetic induction vector

Magnetic induction vector modulus B= F/Ilquantitative characteristic of the field Direction of the magnetic induction vector The magnetic induction vector is directed tangentially to the magnetic induction line.

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Task number 3

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Lines of magnetic induction

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Lines of magnetic induction are called lines, the tangents to which at each point of the field coincide with the direction of the magnetic induction vector.

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Conclusion2:

the vector of magnetic induction - the power characteristic of the magnetic field.

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Types of magnetic fields

A homogeneous magnetic field is called homogeneous if the magnetic induction is the same at all its points. inhomogeneous Define an inhomogeneous magnetic field.

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What fields are shown in the pictures?

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Conclusion3.

The greater the modulus of magnetic induction at a given point in the field, the more force the magnetic field will act on moving charges.

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Anchoring

What does the modulus of the magnetic induction vector depend on? How can it be calculated? A current-carrying conductor is placed in a magnetic field of induction B. After some time, the current in the conductor was reduced by 2 times. Did this change the induction B of the magnetic field in which the conductor was placed? Was the decrease in current accompanied by a change in some other physical quantity? If so, what is this value and how has it changed?

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Solve problems

No. 1. A current of 20A flows through a conductor 45 cm long. What is the induction of the magnetic field in which the conductor is placed if a force of 9 mN acts on the conductor? (Answer: 1 mT) №2. Determine the modulus of force acting on a conductor 20 cm long at a current strength of 10A in a magnetic field with an induction of 0.13 T. (Answer: 0.26 N) №3. A conductor 1.28 m long is located in a uniform magnetic field with an induction of 0.82 T. Determine the force acting on the conductor if the current in it is 18A. (Answer: 19 N)

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Answer the questions

What is the characteristic of a magnetic field called? How to determine the modulus of the magnetic induction vector? What is the unit of measure for magnetic induction called? What is the direction of the magnetic field induction vector? What are called lines of magnetic induction?

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Magnetic field induction

The thinking mind does not feel happy until it succeeds in tying together the disparate facts it observes. Hevesy

Theoretical questions: What is a magnetic field? What generates a magnetic field? Who first discovered the magnetic field around a conductor with current?

How is a magnetic field represented graphically? How to get a picture of magnetic lines using iron filings? What are the magnetic lines of a straight conductor, a solenoid and a permanent magnet?

What does the magnetic field affect? How to experimentally detect the presence of a force acting on a current-carrying conductor in a magnetic field? How to determine the direction of this force? State the left hand rule.

Check homework Determine the direction of the force acting on the conductor c on the side of the permanent magnet Determine the direction of the current strength in the conductor

Without a doubt, all our knowledge begins with experience. Immanuel Kant

Magnetic field induction Conclusion 1: Magnetic fields differ in their strength of action on iron objects, conductors with current and moving charges.

The modulus of the magnetic induction vector F of the magnetic field of the current strength I of the conductor length L F depends on:

F/IL = const B = F/IL Tesla 1Tl =1N/(A m) Conclusion 2: Magnetic induction - power characteristic of a magnet. fields.

The direction of the vector of magnetic induction Conclusion 3: Vector B is directed tangentially to the magnetic lines. The direction of vector B indicates the north pole of the magnetic needle.

Types of magnetic fields: The field is homogeneous The field is inhomogeneous Conclusion 4: The magnetic field is homogeneous if at all its points the magnetic induction is the same both in absolute value and in direction.

Answer the questions: What is the name of the force characteristic of a magnetic field? How is it designated? What formula is used to calculate the modulus of the magnetic induction vector? Can we say that the modulus of magnetic induction depends on the force with which the magnetic. the field acts on a current-carrying conductor, the current strength and the length of the conductor? What is the name of the unit of measurement of magnetic induction. According to figures 120,121,122 (p. 159) determine which fields are homogeneous and which are not.

Take the test and test yourself. Option -1 Option-2 1-A 1-C 2-B 2-A 3-A 3-C 4-A 4-B 5-B,C,D 5-A

Homework: § 46, answer the questions after §, ex: 37 (in writing)

Lesson results I understood and memorized the material of the lesson, I am satisfied with myself. The material seemed to me very difficult and uninteresting, so I got bored.

On the topic: methodological developments, presentations and notes

Independent work “Magnetic field and its image. The action of a magnetic field on a current-carrying conductor. Lorentz force" in 12 variants. Physics grade 9.

This independent work will help to develop the skills of determining the Ampere force, the Lorentz force in physics lessons in grade 9 and as a repetition in lessons in grade 10....

A magnetic field. The action of a magnetic field on a conductor with currents.

Introductory lesson of the section "Electromagnetic field" on the topic "Magnetic field. The action of a magnetic field on a conductor with current.", Grade 9. Lesson developed by technology critical thinking using...

"Magnetic field. The action of a magnetic field on a conductor with current"

This presentation is used in the first lesson on the topic MAGNETIC FIELD. It included the experience of Oersted, the experiments of Ampère, the definition of the magnetic field, the lines of magnetic induction, the definition and formula ...

1. There is a magnetic field around the Earth, how is it created? 2. There are permanent magnets and …………………. Magnets. A magnetic field exists around any conductor with current, i.e. around moving electric charges. Electric current and magnetic field are inseparable from each other. Thus, around stationary electric charges there is only an electric field, around moving charges, i.e. electric current, there is both an electric and a magnetic field. A magnetic field appears around a conductor when a current occurs in the latter, so the current should be considered as a source of a magnetic field. A coil with an iron core inside is called an electromagnet. Coils with current are widely used in technology as magnets. They are convenient in that their magnetic action can be changed. The magnetic effect of a coil with current is stronger, the greater the number of turns in it. With an increase in the current strength, the effect of the magnetic field of the coil with current increases, with a decrease, it weakens. The iron introduced inside the coil enhances the magnetic effect of the coil. A coil with an iron core inside is called an electromagnet.

Magnetic separator Very fine iron filings are mixed into the grain. These sawdust do not stick to smooth grains of useful cereals, but stick to weed grains. Grains 1 are poured out of the hopper onto a rotating drum 2. There is a strong electromagnet inside the drum. By attracting iron particles 4, it carries away the weed grains from the grain flow 3 and in this way the grain is cleared of weeds and iron objects that have accidentally fallen.

The magnetic field is characterized by a vector physical quantity, which is denoted by a symbol and is called the magnetic field induction (or magnetic induction). The module of this force depends on the magnetic field itself. In addition, the strength of the magnetic field on the conductor is proportional to the length l of this conductor and the current strength I in it.

Nikola Tesla Usually, the mention of the name of this scientist in school textbooks is associated with the unit of magnetic induction (1 Tesla), named after him. He was a brilliant inventor and scientist who was ahead of his time. During his life, N. Tesla made about 1000 different inventions and discoveries, received almost 800 patents for inventions in various fields of technology. There were a variety of rumors about him, he was called a sorcerer and a hoaxer. Tesla went so far from official science that even today most of his works remain incomprehensible and inexplicable.

Tesla's obsession with science knew no bounds. He set aside four hours for sleep, of which two were usually spent thinking over ideas. Lord Kelvin wrote of him as "the most devoted electrical science man of all his contemporaries." After 1900, he received many patents for inventions in various fields of technology. He discovered alternating current, fluorescent light, wireless power transmission, built the first electric clock, a solar-powered engine. He invented the radio before Markoni and Popov, received a three-phase current before Dolivo-Dobrovolsky. On his patents, the entire energy industry of the 20th century grew. In 1917, Tesla received the Edison Medal, the highest honor bestowed by the American Institute of Electrical Engineers. In the 1930s he was awarded the Nobel Prize. But he refused to accept it, not wanting to share it with Edison, whom he never forgave to the end of his days for criticizing alternating current.

Lectures by Nikola Tesla were a colorful show, and accusations of magic constantly accompanied Tesla's activities. Tesla was pulling out of his briefcase a small transformer that operated on high-frequency, high-voltage alternating current at extremely low amperage. When he turned it on, lightning began to writhe around him. And he calmly caught them with his hands, while people from the first places in the hall hastily moved back.

In 1893, Tesla put on a show at the World's Fair in Chicago. Standing on a podium in the center of the exhibition hall, he passed through himself a current of two million volts. According to Edison, not even dust should have remained from a crazy Serb. However, Tesla was smiling calmly, and in his hand Edison's light bulb was burning, receiving energy as if from nowhere. Now we know that the high-frequency current passes only through the surface, without harming a person. Then this trick seemed like a miracle.

A good show was the experiment with light bulbs. Tesla turned on his transformer and an ordinary light bulb began to glow in his hands. It was already amazing. When he took out a light bulb without a filament from his briefcase, just an empty bulb, and it still glowed anyway, there was no limit to the surprise of the listeners. Or in the course of his lecture on the high-frequency electromagnetic field in front of the scientists of the Royal Academy, Tesla turned on and off the electric motor remotely, in his hands the electric bulbs lit up by themselves. Then it was 1892!

Wireless energy transfer idea Tesla was fascinated by the idea of ​​transmitting energy over a distance without wires and he managed to achieve outstanding success in this area. In Tesla publicly demonstrates the possibility of transmission electrical energy without wires over long distances and conducts a grand experience on wireless power transmission. He claimed to have made the most important discovery - terrestrial stationary waves. The earth can serve as a conductor.

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Lesson - lecture "Magnetic field. Permanent magnets and the magnetic field of the current. Magnetic field induction » Regional State Autonomous educational institution middle vocational education Belgorod Construction College Belgorod

For the first time, the connection between electrical and magnetic phenomena was discovered in 1820 by Hans Christian Oersted: if a magnetic needle is placed over a conductor directed along the earth's meridian, which points to the north, and an electric current is passed through the conductor, then the arrow deviates by a certain angle.

In 1820, André Ampere discovered the law of the interaction of conductors with current

The magnetic field is a special form of matter, through which the interaction between moving charged particles is carried out. Basic properties of the magnetic field: The magnetic field is generated by electric current (moving charges). The magnetic field is detected by the effect on the electric current (moving charges). The magnetic field really exists independently of us, of our knowledge about it.

Magnet - a body with its own magnetic field Types of magnets: Natural magnets (magnetic ore) are formed when ore containing iron or iron oxides is cooled and magnetized due to terrestrial magnetism. Temporary magnets - act like permanent magnets only when they are in a strong magnetic field, and lose their magnetism when the magnetic field disappears (paper clips and nails). Electromagnets - a metal core with an induction coil through which an electric current passes.

You can't separate the poles of a magnet!

Magnetic field and its graphic representation We agreed to take the direction of the northern end of the magnetic needle as the direction. Lines of force coming out north pole, and enter, respectively, into the south pole of the magnet. Lines of magnetic induction are called curves, the tangents to which at each point coincide with the direction of the vector at this point.

Gimlet rule: if the direction of the translational movement of the gimlet coincides with the direction of the current in the conductor, then the direction of rotation of the gimlet handle coincides with the direction of the magnetic induction vector.

gimlet rule

An important feature of magnetic induction lines is that they have neither beginning nor end. They are always closed. Fields with closed lines of force are called vortex fields. The magnetic field is a vortex field. Magnetic lines of a straight conductor Magnetic lines of a solenoid (coil)

Field lines of a magnet The configuration of the field lines of a magnet is easy to establish with the help of small iron filings, which are magnetized in the studied magnetic field and behave like small magnetic needles (turn along the lines of force). Magnetic field of like poles Magnetic field of unlike poles

The formula for the relationship between the magnetic induction vector and the magnetic field strength: - magnetic induction vector (Tl) - magnetic field strength (A / m) - magnetic permeability of the medium (for vacuum = 1) - magnetic constant

Biot - Savart - Laplace law: H - magnetic field strength at a given point (A / m) I - current strength (A) l - length of the conductor section (m) r - radius vector connecting the conductor section with the considered point of the field, the angle between the direction of the current in the section and the radius vector

Main sources: Gendenstein L.E. Dick Yu.I. Physics. Textbook for 11 cells. - M., 2005. Dmitrieva V.F. Problems in physics: textbook. allowance. - M., 2003. Collection of problems and questions in physics, ed. R.A. Gladkova.- M., 2003. Additional sources: Gromov S.V. Sharonova N.V. Physics, 10-11: A book for the teacher. - M., 2004. Kasyanov V.A. Guidelines on the use of textbooks by V.A. Kasyanov “Physics. Grade 10”, “Physics. 11 cl." in the study of physics at the basic and profile level. - M., 2006. Kasyanov V.A. Physics. 10, 11 cells. Thematic and lesson planning. - M., 2002. Federal component of the state standard of general education / Ministry of Education of the Russian Federation. – M., 2004. Internet resources youtube .com http:// www.kakprosto.ru http:// ru.wikipedia.org / http:// allforchildren.ru / why /whatis37.php http:// elektrobgau.narod .ru /