Bibliographic description: Nasekin K. G., Mayurov S. G. Obtaining a picture magnetic field// Young scientist. 2015. No. 1. P. 75-78..04.2019).

Introduction. Magnetism

Natural magnets, simply put, are pieces of magnetic iron ore - magnetite ( chemical composition: 31% iron and 69% oxygen) were not always called magnets. IN different countries the magnet has been called differently, but most of all these names are translated as “loving.” This is how the poetic language of the ancients describes the property of pieces of a magnet - to attract iron.

“Loving stone” is the poetic name the Chinese gave to a natural magnet. The strength of natural magnets is insignificant, and therefore the Greek name for the magnet is translated as “Hercules stone”.

You should not think that a magnet only acts on iron. There are a number of other bodies that also experience the effect strong magnet, although not to the same extent as iron. Metals: nickel, cobalt, manganese, platinum, gold, silver, aluminum are weakly attracted by a magnet. Another remarkable property of the so-called diamagnetic bodies, for example zinc, lead, sulfur, bismuth: these bodies are repelled by a strong magnet!

Liquids and gases also experience the attraction or repulsion of a magnet, although to a very weak extent; the magnet must be very strong to exert its influence on these substances.

Main part

Lines of magnetic forces

A person does not have a sense organ that perceives a magnetic field, so he can only guess about the existence of magnetic forces that surround a magnet. However, it is not difficult to indirectly detect patterns of distribution of these forces. The best way to do this is with fine iron filings.

To do this, you need to take a magnet and cover it with a glass plate on top. Place a sheet of paper on the plate. Next, pour the sawdust in a thin, even layer onto a sheet of paper, shaking the sawdust with light blows. Magnetic forces pass freely through paper and glass; therefore, iron filings will become magnetized under the influence of a magnet; when we shake them, they momentarily separate from the plate and can easily rotate under the influence of magnetic forces.

As a result, the sawdust is arranged in rows, clearly revealing the distribution of invisible magnetic lines. Magnetic forces create complex system curved lines. You can see how they diverge radiantly from each pole of the magnet. The closer to the pole, the thicker and clearer the lines of sawdust; on the contrary, with distance from the pole they become rarefied and lose their distinctness, clearly demonstrating the weakening of magnetic forces with distance.

Relevance of the work

The work is devoted to improving the obtaining of magnetic field patterns that clearly show magnetic lines. Using known methods To obtain flat patterns, it is necessary to develop a method for obtaining three-dimensional patterns of the magnetic field.

Capturing an image using a magnet and iron filings

To get such a drawing, you need to take: a magnet, small glass, a sheet of paper, iron filings. First, we placed the magnet on the workbench, then covered it with glass. A sheet of paper was placed on the glass, after which iron filings were sprinkled. To make it work beautiful drawing need to:

1) Do not sprinkle iron filings from a small height from the magnet. This causes the sawdust to clump together in the air and fall onto the leaf in a heap.

2) It is better to sprinkle iron filings near the poles so that the magnetic lines are clearly visible.

The effect of a magnetic field on a display screen

The magnetic field of the magnet also affects the display screen. If you take a magnet and bring it to the display screen, many different things happen:

1. Distortion of the image on the display screen.

2. Change the color palette of the display screen.

If you bring a magnet directly to the display glass, a unique and beautiful picture appears on it. As the magnet moves away from the screen, the picture becomes less clear. In the photographs taken at this moment, you can see a certain pattern. If two ring-shaped magnets are placed on the display screen, a pattern is formed that is different from the pattern formed by one magnet. At the border of these drawings you can see lines that are somehow related to the magnetic field. If the number of magnets changes or the location of the magnet poles changes, then the pattern will be different. If a ring-shaped magnet with high magnetic force is placed on the display screen, the display screen will become dark, and inside the ring the screen will glow with different colors.

The book says that a magnetic field acts on electrons. In this interaction, electrons do not enter the Right place and distortions occur. The experiments were carried out on an old monitor.

Obtaining three-dimensional magnetic field images

During the work, patterns of the magnetic field of various magnets were obtained and photographed using iron filings. When analyzing the results, it was noticed that the magnetic field patterns are either flat or the sawdust rises to a small height, and do not provide complete information about the magnetic field. After all, in order to obtain pictures of the magnetic field of even one magnet, you need to do several experiments. To obtain a picture of the magnetic field of one magnet, one experiment is needed, of another magnet - a second experiment. The question arose: how to obtain magnetic field patterns in volume? What needs to be done to get a volumetric picture of the magnetic field? A problem arises, the force of gravity acting on the iron filings interferes. To solve this problem, you need to reduce the weight of the sawdust. Reduce body weight in normal conditions only possible with liquid. In this case, glycerin liquid is suitable. Advantages of this liquid:

1. Has a higher density than water = 1260 kg/m3

2. Glycerin is transparent.

3. Glycerin is harmless to human health.

4. Glycerin has good viscosity.

If you take water, the buoyant force will be less. Why? Water has a lower density than glycerin. Water has low viscosity.

Description of equipment

Two vessels were taken in the form rectangular parallelepiped made of plexiglass, dimensions 85 x 85 x 55 mm. One vessel is not sealed, in case you need to add sawdust or glycerin, but it is closed with bronze bolts and becomes airtight. To seal the vessel, the surface of the edges of the vessel was smeared with epoxy resin, and the lid was pressed tightly against the vessel. Another vessel for displaying magnetic field paintings was made, but two iron metal rods were left in it. Before sealing the vessel, you need to pour glycerin into it and add iron filings. To do the experiments, you need to thoroughly mix the glycerin and sawdust, rotating the vessel in your hand.

1. You need to take a vessel without rods and mix the sawdust in glycerin with sharp movements and place it on a magnet with high magnetic force. Then the iron filings will build a three-dimensional pattern of magnetic lines not only at the bottom of the vessel, but also on long distance from the bottom.

2. You need to take a vessel with rods and mix it with sharp movements and place it on a magnet. Then the iron filings will build a three-dimensional pattern near the rods and at the bottom of the vessel.

It takes several minutes for the iron filings to build a three-dimensional picture of the magnetic field. Then you can remove the vessel and place the magnet in another place and the picture will appear again. But it is better to leave the vessel for a day, since glycerin is slightly cloudy, so the picture will appear better.

By using epoxy resin, iron filings in a small plastic box was an attempt to obtain a picture of the magnetic field. The experiment was a success, but it needs to be repeated.

My impressions: after seeing these phenomena, I was amazed at this property of the magnet. For me this is very interesting and exciting. Depending on the type of magnet, the magnetic field patterns are different. Pictures of the magnetic field always turn out beautiful, they can change.

Magnets in the air

When experiments were carried out to obtain magnetic field patterns, the following happened: when the magnet moved under the glass, the iron filings moved along with the magnet and changed the angle of inclination and height. The question arose: what would happen if pieces of magnets were placed in a changing magnetic field? If you connect a wire coil with an iron core to a current source, a magnetic field will be generated. If iron filings are placed next to a coil of wire, a picture of the magnetic field can be obtained. If you connect it to a DC source (battery, accumulator), then the iron filings will create a stationary magnetic field pattern. And if to the source alternating current, then you can hear a faint hum, which means the sawdust is vibrating. This can be used for experiments. Let's consider the course of the experiment:

1. Take foam balls and place broken magnet pieces into them.

3. After this, place the foam balls with pieces of magnets in the box.

4. Place the box of balls on the reel.

5. Coil of copper wire connect to an AC power source.

As a result of the action of a magnetic field on fragments of magnets in balls from the action of experiment, a chaotic movement of molecules is created in the magnetic field.

Home magnets

In my family, magnetic souvenirs can be seen on the refrigerator. These magnets are, so to speak, decorative. We get them from relatives, acquaintances who were on vacation somewhere, or we bring them ourselves from vacation, as a tradition.

But the most important use of refrigerator magnets is hidden from our eyes. In refrigerators, strip magnets are used in door seals. With this, the door is attracted to the body and a seal occurs; moisture does not enter the refrigerator.

We also have a tool kit that contains magnetized screwdrivers. Such screwdrivers are needed in order not to lose any screw. There are curtains at home; magnetic clips are hung on them to give the desired shape. There is also a simple magnet on which we hang our house keys so they don’t get lost. Previously, a music center was used at home, which had two speakers, these speakers have magnets. IN household appliances Magnets are often used.

There are souvenirs whose operating principle is based on the use of the magnetic field of magnets. I have special magnets from which you can make different chains. In the physics classroom there is a souvenir “horizontal spinning top”. The tip of the spinning top rests on the glass, it hangs above the stand and can be untwisted. There is a game of darts. Modern darts are based on the action of a magnet; the dart has a magnet at the tip.

Work results

1. Pictures of the magnetic field of magnets of different shapes were obtained;

2. Pictures of the magnetic field of magnets with different magnetic strengths were obtained;

3. Pictures of distortion of screen images on the display were obtained;

4. Three-dimensional pictures of magnetic fields of magnets were obtained different forms and different magnetic strength;

5. A collection of photographic images of magnetic field patterns on digital media has been compiled;

6. A model of moving magnets in an alternating magnetic field was made;

7. An attempt was made to obtain an “eternal” picture of the magnetic field.

8. The work can be continued to obtain more complex patterns of magnetic fields.

conclusions

1. Patterns of magnetic fields are varied.

2. Their type depends:

a) - on the shape of the magnet;

b) - from magnetic force;

c) - on the presence of poles.

3. The magnetic field acts on the image on the screen of an old display or TV and various phenomena occur

a) - the appearance of spots on the display screen;

b) - distortion of the image on the display screen;

c) - changing the color palette of the display screen;

d) in the arrangement of spots on the display screen, some kind of pattern is guessed.

4. Three-dimensional paintings magnetic field give more information about the location of magnetic lines.

5. An alternating magnetic field causes magnets to move.

Literature:

1. Kartsev V.P. Adventures of great equations, publishing house "Knowledge" M. - 1978

2. Perelman Ya. I. Entertaining physics, publishing house “Science” M.-1972

3. A. S. Enochovich. Handbook of physics and technology, publishing house "Prosveshchenie" M. - 1983

4. A. Shileiko, T. Shileiko Electrons...electrons, publishing house "Children's Literature" M. - 1983

5. L. V. Tarasov Physics in Nature M.: Education, 1998

Graphic representation of the magnetic field. Magnetic induction vector flux

The magnetic field can be represented graphically using magnetic induction lines. A magnetic induction line is a line whose tangent at each point coincides with the direction of the magnetic field induction vector (Fig. 6).

Research has shown that magnetic induction lines are closed lines that enclose currents. The density of magnetic induction lines is proportional to the magnitude of the vector in this place fields. In the case of a direct current magnetic field, the magnetic induction lines have the shape of concentric circles lying in planes perpendicular to the current, with the center on the straight line with the current. The direction of magnetic induction lines, regardless of the shape of the current, can be determined using the gimlet rule. In the case of a direct current magnetic field, the gimlet must be rotated so that its translational movement coincides with the direction of the current in the wire, then the rotational movement of the gimlet handle will coincide with the direction of the magnetic induction lines (Fig. 7).

In Fig. 8 and 9 show pictures of the magnetic induction lines of the circular current field and the solenoid field. A solenoid is a collection of circular currents with a common axis.

The lines of the induction vector inside the solenoid are parallel to each other, the density of the lines is the same, the field is uniform (= const). The solenoid field is similar to the field permanent magnet. The end of the solenoid from which the induction lines emerge is similar to the north pole - N, the opposite end of the solenoid is similar to the south pole - S.

The number of lines of magnetic induction that penetrate a particular surface is called the magnetic flux through that surface. Designate magnetic flux letter Ф in (or Ф).

,

(3)

Where α is the angle formed by the vector and the normal to the surface (Fig. 10).

– projection of the vector onto the normal to the area S.

The magnetic flux is measured in webers (Wb): [F]=[B]× [S]=T× m 2 = =

Topics of the Unified State Examination codifier: interaction of magnets, magnetic field of a conductor with current.

The magnetic properties of matter have been known to people for a long time. Magnets got their name from the ancient city of Magnesia: in its vicinity the mineral (later named magnetic iron ore or magnetite), pieces of which attracted iron objects.

Magnet interaction

On two sides of each magnet there are North Pole And South Pole. Two magnets are attracted to each other by opposite poles and repelled by like poles. Magnets can act on each other even through a vacuum! All this resembles interaction electric charges, however the interaction of magnets is not electrical. This is evidenced by the following experimental facts.

Magnetic force weakens as the magnet heats up. The strength of the interaction of point charges does not depend on their temperature.

The magnetic force weakens if the magnet is shaken. Nothing like this happens with electrically charged bodies.

Positive electrical charges can be separated from negative ones (for example, when electrifying bodies). But it is impossible to separate the poles of a magnet: if you cut a magnet into two parts, then poles also appear at the cut site, and the magnet splits into two magnets with opposite poles at the ends (oriented in exactly the same way as the poles of the original magnet).

So magnets Always bipolar, they exist only in the form dipoles. Isolated magnetic poles (called magnetic monopoles- analogues of electric charge) do not exist in nature (in any case, they have not yet been discovered experimentally). This is perhaps the most striking asymmetry between electricity and magnetism.

Like electrically charged bodies, magnets act on electric charges. However, the magnet only acts on moving charge; if the charge is at rest relative to the magnet, then the effect of magnetic force on the charge is not observed. On the contrary, an electrified body acts on any charge, regardless of whether it is at rest or in motion.

According to modern concepts of short-range theory, the interaction of magnets is carried out through magnetic field Namely, a magnet creates a magnetic field in the surrounding space, which acts on another magnet and causes a visible attraction or repulsion of these magnets.

An example of a magnet is magnetic needle compass. Using a magnetic needle, you can judge the presence of a magnetic field in a given region of space, as well as the direction of the field.

Our planet Earth is a giant magnet. Not far from the north geographic pole of the Earth is the south magnetic pole. Therefore, the north end of the compass needle, turning towards the south magnetic pole of the Earth, points to geographic north. This is where the name “north pole” of a magnet came from.

Magnetic field lines

The electric field, we recall, is studied using small test charges, by the effect on which one can judge the magnitude and direction of the field. The analogue of a test charge in the case of a magnetic field is a small magnetic needle.

For example, you can get some geometric insight into the magnetic field by placing very small compass needles at different points in space. Experience shows that the arrows will line up along certain lines - the so-called magnetic field lines. Let us define this concept in the form of the following three points.

1. Magnetic field lines, or magnetic lines of force, are directed lines in space that have the following property: a small compass needle placed at each point on such a line is oriented tangent to this line.

2. The direction of the magnetic field line is considered to be the direction of the northern ends of the compass needles located at points on this line.

3. The denser the lines, the stronger the magnetic field in a given region of space..

Iron filings can successfully serve as compass needles: in a magnetic field, small filings become magnetized and behave exactly like magnetic needles.

So, by pouring iron filings around a permanent magnet, we will see approximately the following picture of magnetic field lines (Fig. 1).

Rice. 1. Permanent magnet field

The north pole of a magnet is indicated by the color blue and the letter ; the south pole - in red and the letter . Please note that the field lines leave the north pole of the magnet and enter the south pole: after all, it is towards the south pole of the magnet that the north end of the compass needle will be directed.

Oersted's experience

Despite the fact that electrical and magnetic phenomena have been known to people since antiquity, there is no relationship between them for a long time was not observed. For several centuries, research into electricity and magnetism proceeded in parallel and independently of each other.

The remarkable fact that electrical and magnetic phenomena are actually related to each other was first discovered in 1820 - in the famous experiment of Oersted.

The diagram of Oersted's experiment is shown in Fig. 2 (image from the site rt.mipt.ru). Above the magnetic needle (and are the north and south poles of the needle) there is a metal conductor connected to a current source. If you close the circuit, the arrow turns perpendicular to the conductor!
This simple experiment directly indicated the relationship between electricity and magnetism. The experiments that followed Oersted's experiment firmly established the following pattern: magnetic field is generated by electric currents and acts on currents.

Rice. 2. Oersted's experiment

The pattern of magnetic field lines generated by a current-carrying conductor depends on the shape of the conductor.

Magnetic field of a straight wire carrying current

The magnetic field lines of a straight wire carrying current are concentric circles. The centers of these circles lie on the wire, and their planes are perpendicular to the wire (Fig. 3).

Rice. 3. Field of a straight wire with current

There are two alternative rules for determining the direction of forward magnetic field lines.

Clockwise rule. The field lines go counterclockwise if you look so that the current flows towards us.

Screw rule(or gimlet rule, or corkscrew rule- this is something closer to someone ;-)). The field lines go where you need to turn the screw (with a regular right-hand thread) so that it moves along the thread in the direction of the current.

Use the rule that suits you best. It is better to get used to the clockwise rule - you will later see for yourself that it is more universal and easier to use (and then remember it with gratitude in your first year, when you study analytical geometry).

In Fig. 3 something new has appeared: this is a vector called magnetic field induction, or magnetic induction. The magnetic induction vector is an analogue of the tension vector electric field: he serves power characteristic magnetic field, determining the force with which the magnetic field acts on moving charges.

We will talk about forces in a magnetic field later, but for now we will only note that the magnitude and direction of the magnetic field is determined by the magnetic induction vector. At each point in space, the vector is directed in the same direction as the northern end of the compass needle placed at a given point, namely, tangent to the field line in the direction of this line. Magnetic induction is measured in Tesla(Tl).

As in the case of the electric field, for the magnetic field induction the following applies: superposition principle. It lies in the fact that inductions of magnetic fields created at a given point by various currents add up vectorially and give the resulting vector of magnetic induction:.

Magnetic field of a coil with current

Consider a circular coil along which circulates D.C.. We do not show the source that creates the current in the figure.

The picture of the field lines of our orbit will look approximately as follows (Fig. 4).

Rice. 4. Field of a coil with current

It will be important for us to be able to determine into which half-space (relative to the plane of the coil) the magnetic field is directed. Again we have two alternative rules.

Clockwise rule. The field lines go there, looking from where the current appears to circulate counterclockwise.

Screw rule. The field lines go where the screw (with a normal right-hand thread) will move if rotated in the direction of the current.

As you can see, the current and the field change roles - compared to the formulation of these rules for the case of direct current.

Magnetic field of a current coil

Coil It will work if you wind the wire tightly, turn to turn, into a sufficiently long spiral (Fig. 5 - image from en.wikipedia.org). The coil may have several tens, hundreds or even thousands of turns. The coil is also called solenoid.

Rice. 5. Coil (solenoid)

The magnetic field of one turn, as we know, does not look very simple. Fields? individual turns of the coil are superimposed on each other, and it would seem that the result should be a very confusing picture. However, this is not so: the field of a long coil has an unexpectedly simple structure (Fig. 6).

Rice. 6. current coil field

In this figure, the current in the coil flows counterclockwise when viewed from the left (this will happen if in Fig. 5 the right end of the coil is connected to the “plus” of the current source, and the left end to the “minus”). We see that the magnetic field of the coil has two characteristic properties.

1. Inside the coil, far from its edges, the magnetic field is homogeneous: at each point the magnetic induction vector is the same in magnitude and direction. Field lines are parallel straight lines; they bend only near the edges of the coil when they come out.

2. Outside the coil the field is close to zero. The more turns in the coil, the weaker field outside of her.

Note that an infinitely long coil does not release the field outward at all: there is no magnetic field outside the coil. Inside such a coil, the field is uniform everywhere.

Doesn't remind you of anything? A coil is the “magnetic” analogue of a capacitor. You remember that a capacitor creates a homogeneous electric field, the lines of which bend only near the edges of the plates, and outside the capacitor the field is close to zero; a capacitor with infinite plates does not release the field to the outside at all, and the field is uniform everywhere inside it.

And now - the main observation. Please compare the picture of the magnetic field lines outside the coil (Fig. 6) with the magnet field lines in Fig. 1 . It's the same thing, isn't it? And now we come to a question that has probably arisen in your mind for a long time: if a magnetic field is generated by currents and acts on currents, then what is the reason for the appearance of a magnetic field near a permanent magnet? After all, this magnet does not seem to be a conductor with current!

Ampere's hypothesis. Elementary currents

At first it was thought that the interaction of magnets was explained by special magnetic charges concentrated at the poles. But, unlike electricity, no one could isolate the magnetic charge; after all, as we have already said, it was not possible to obtain the north and south poles of a magnet separately - the poles are always present in a magnet in pairs.

Doubts about magnetic charges were aggravated by Oersted's experiment, when it turned out that the magnetic field is generated by electric current. Moreover, it turned out that for any magnet it is possible to select a conductor with a current of the appropriate configuration, such that the field of this conductor coincides with the field of the magnet.

Ampere put forward a bold hypothesis. There are no magnetic charges. The action of a magnet is explained by closed electric currents inside it.

What are these currents? These elementary currents circulate inside atoms and molecules; they are associated with the movement of electrons along atomic orbits. The magnetic field of any body consists of the magnetic fields of these elementary currents.

Elementary currents can be randomly located relative to each other. Then their fields are mutually cancelled, and the body does not exhibit magnetic properties.

But if the elementary currents are arranged in a coordinated manner, then their fields, adding up, reinforce each other. The body becomes a magnet (Fig. 7; the magnetic field will be directed towards us; the north pole of the magnet will also be directed towards us).

Rice. 7. Elementary magnet currents

Ampere's hypothesis about elementary currents clarified the properties of magnets. Heating and shaking a magnet destroys the order of its elementary currents, and the magnetic properties weaken. The inseparability of the poles of the magnet has become obvious: at the point where the magnet is cut, we get the same elementary currents at the ends. The ability of a body to be magnetized in a magnetic field is explained by the coordinated alignment of elementary currents that “turn” properly (read about the rotation of a circular current in a magnetic field in the next sheet).

Ampere's hypothesis turned out to be true - this was shown by the further development of physics. Ideas about elementary currents became an integral part of the theory of the atom, developed already in the twentieth century - almost a hundred years after Ampere’s brilliant guess.

We know that a current-carrying conductor creates a magnetic field around itself. A permanent magnet also creates a magnetic field. Will the fields they create be different? Undoubtedly they will. The difference between them can be seen clearly if you create graphical images of magnetic fields. The magnetic field lines will be directed differently.

Uniform magnetic fields

When current carrying conductor magnetic lines form closed concentric circles around a conductor. If we look at a cross-section of a current-carrying conductor and the magnetic field it creates, we will see a set of circles various diameters. The figure on the left shows just a conductor carrying current.

The closer you are to the conductor, the stronger the effect of the magnetic field. As you move away from the conductor, the action and, accordingly, the strength of the magnetic field will decrease.

When permanent magnet we have lines coming out of the south pole of the magnet, passing along the body of the magnet itself and entering its north pole.

Having sketched such a magnet and the magnetic lines of the magnetic field formed by it graphically, we will see that the effect of the magnetic field will be strongest near the poles, where the magnetic lines are most densely located. The picture on the left with two magnets just depicts the magnetic field of permanent magnets.

We will see a similar picture of the location of magnetic lines in the case of a solenoid or coil with current. The magnetic lines will have the greatest intensity at the two ends or ends of the coil. In all the above cases we had a non-uniform magnetic field. The magnetic lines had different direction, and their density was different.

Can a magnetic field be uniform?

If we look closely graphic image solenoid, we will see that the magnetic lines are parallel and have the same density in only one place inside the solenoid.

The same picture will be observed inside the body of a permanent magnet. And if in the case of a permanent magnet we cannot “climb” inside its body without destroying it, then in the case of a coil without a core or solenoid, we get a uniform magnetic field inside them.

Such a field may be required by a person in a number of technological processes, so it is possible to construct solenoids of sufficient size to allow necessary processes inside them.

Graphically, we are accustomed to depicting magnetic lines as circles or segments, that is, we seem to see them from the side or along. But what if the drawing is created in such a way that these lines are directed towards us or at reverse side from U.S? Then they are drawn in the form of a dot or a cross.

If they are directed at us, then they are depicted as a point, as if it were the tip of an arrow flying towards us. In the opposite case, when they are directed away from us, they are drawn in the form of a cross, as if it were the tail of an arrow moving away from us.

Oersted's experiment in 1820. What does the deviation of the magnetic needle indicate when closing electrical circuit? There is a magnetic field around a conductor carrying current. This is what the magnetic needle reacts to. The source of the magnetic field is moving electric charges or currents.

Oersted's experiment in 1820. What does the fact that the magnetic needle turned to indicate? This means that the direction of the current in the conductor has been reversed.

Ampere's experiment in 1820. How to explain the fact that current-carrying conductors interact with each other? We know that a magnetic field acts on a current-carrying conductor. Therefore, the phenomenon of interaction of currents can be explained as follows: electricity in the first conductor generates a magnetic field that acts on the second current and vice versa...

Unit of current If a current of 1 A flows through two parallel conductors 1 m long, located at a distance of 1 m from each other, then they interact with a force N.

The unit of current is 2 A. What is the current strength in the conductors if they interact with a force H?

What is a magnetic field and what are its properties? 1.MP is special shape matter that exists independently of us and our knowledge about it. 2.MF is generated by moving electric charges and is detected by its effect on moving electric charges. 3. With distance from the MF source it weakens.

Properties of magnetic lines: 1. Magnetic lines are closed curves. What does this mean? If you take a piece of magnet and break it into two pieces, each piece will again have a "north" and a "south" pole. If you again break the resulting piece into two parts, each part will again have a “north” and a “south” pole. It doesn’t matter how small the resulting pieces of magnets are, each piece will always have a “north” and a “south” pole. It is impossible to achieve a magnetic monopole ("mono" means one, monopole means one pole). At least this is the modern point of view on this phenomenon. This suggests that magnetic charges do not exist in nature. Magnetic poles cannot be divided.

2. A magnetic field can be detected by... A) by the action on any conductor, B) by the action on a conductor through which an electric current flows, C) a charged tennis ball suspended on a thin inextensible thread, D) on moving electric charges. a) A and B, b) A and B, c) B and C, d) B and D.

7.Which statements are true? A. Electric charges exist in nature. B. Magnetic charges exist in nature. B. Electric charges do not exist in nature. D. There are no magnetic charges in nature. a) A and B, b) A and B, c) A and D, d) B, C and D.

10. Two parallel conductors 1 m long, located at a distance of 1 m from each other, when an electric current flows through them, are attracted with a force N. This means that currents flow through the conductors... a) in opposite directions, 1 A each, b ) one direction at 1 A, c) opposite directions at 0.5 A, d) one direction at 0.5 A.

23. A magnetic needle will deviate if it is placed near... A) near a flow of electrons, B) near a flow of hydrogen atoms, C) near a flow of negative ions, D) near a flow of positive ions, E) near a flow of oxygen atom nuclei. a) all answers are correct, b) A, B, C, and D, c) B, C, D, d) B, C, D, E

3. The figure shows a cross-section of a conductor with current at point A; the electric current enters perpendicularly to the plane of the figure. Which of the directions presented at point M corresponds to the direction of vector B of the induction of the magnetic field of the current at this point? a) 1, b) 2, c) 3, 4)