Improved: 10.03.16
About magnets
Magnet - a body that has a magnetization.
Field is a space within which one object (Source) acts, not necessarily by direct contact, on another object (Receiver). If the Source of influence is a magnet, then the field is considered to be magnetic.
A magnetic field is the space around everyone from the poles of a magnet and for this reason it has no limits in all directions ! The center of each magnetic field is the corresponding pole of the magnet.
There can be more than one Source at the same time in some limited space. The intensity of these Sources will not necessarily be the same. Accordingly, there can also be more than one center.
The resulting field in this case will not be uniform. At each Receiver point of such a field, the intensity will correspond to the sum of the intensities of the magnetic fields formed by all centers.
In this case, the northern magnetic fields and the southern magnetic fields should conditionally be considered as having opposite signs. For example, if at some point of the total field the intensity of the southern magnetic field located in it coincides with the intensity of the northern magnetic field located here, then the total intensity at the discussed Receiver point from the interaction of both fields will be equal to zero.
Permanent magnet - a product capable of maintaining its magnetization after turning off the external magnetic field.
Electromagnet - a device whose magnetic field is created in the coil only when an electric current flows through it.
The general property of any magnet, regardless of the type of magnetic field (north or south) isattraction to materials containing iron (Fe ) . With bismuth, an ordinary magnet works on repulsion. Physics cannot explain either effect, although an unlimited number of hypotheses can be proposed. ! Some grades of stainless steel, which also contain iron, are excluded from this rule (“attraction”) - this feature cannot be explained by physics either, although an unlimited number of hypotheses can also be offered. !
magnetic pole one side of the magnet. If the magnet is suspended by the middle part so that the poles have a vertical orientation and it (the magnet) can freely rotate in a horizontal plane, then one of the sides of the magnet will turn towards the north pole of the Earth. Accordingly, the opposite side will turn towards the south pole. The side of a magnet that points toward the north pole of the earth is calledsouth pole magnet, and the opposite side -north pole magnet.
The magnet attracts other magnets and objects made of magnetic materials without even being in contact with them. Such action at a distance is explained by the existencemagnetic field in space around both magnetic poles of a magnet.
Opposite poles of two magnets usually are attracted to each other , and names of the same name - usually mutuallyrepel .
Why "usually"? Yes, because sometimes there are anomalous phenomena, when, for example, opposite poles neither attract mutually nor repel ! This phenomenon has a namemagnetic pit ". Physics can't explain it !
In my experiments, there were also situations where like poles attract (instead of the expected mutual repulsion), and opposite poles repel (instead of the expected mutual attraction) ! This phenomenon does not even have a name, and physics, too, cannot yet explain it. !
If a piece of non-magnetized iron is brought near one of the poles of a magnet, the latter will temporarily become magnetized.
Such material is considered to be magnetic.
In this case, the edge of the piece closest to the magnet will become a magnetic pole, the name of which is opposite to the name of the near pole of the magnet, and the far end of the piece will become a pole of the same name as the near pole of the magnet.
In this case, two opposite poles of two magnets are in the zone of mutual action: the Source magnet and the conditional magnet (from a piece of iron).
It was mentioned above that in the space between these magnets, the algebraic addition of the intensities of the interacting fields takes place. And, since the fields turn out to be of different signs, a zone of a total magnetic field with zero (or almost zero) intensity is formed between the magnets. In what follows, I will refer to such a zone as "Zerozone ».
Since "Nature does not tolerate emptiness", it can be assumed that she (Nature) seeks to fill the emptiness with the nearest available "at hand" material. In our case, such material is magnetic fields, between which a zero zone (Zerouzon) has formed. To do this, it is required to bring both Sources of different signs closer together (to bring the centers of magnetic fields closer) until the zero zone between the fields completely disappears. ! Unless, of course, nothing prevents the movement of centers (the approach of magnets) !
Here is an explanation for the mutual attraction of opposite magnetic poles and the mutual attraction of a magnet with a piece of iron !
By analogy with attraction, we can consider the phenomenon of repulsion.
In this variant, one-sign magnetic fields appear in the zone of mutual influence. Of course, they are also algebraically added to each other. Because of this, at the Receiver points between the magnets, a zone arises with an intensity higher than the intensities in neighboring areas. In what follows, I will refer to such a zone as "Maxison ».
It is logical to assume that Nature strives to balance this trouble and move the centers of the interacting fields away from each other in order to smooth out the intensity of the field in the Maxison.
With this explanation, it turns out that none of the poles of the magnet can move the piece of iron away from itself by itself ! Because a piece of iron, being in a magnetic field, will always turn into a conditional temporary magnet and, therefore, magnetic poles will always form on it (on a piece of iron). Moreover, the near pole of the newly formed temporary magnet is opposite to the pole of the Source magnet. Therefore, a piece of iron located in the magnetic field of the Source Pole will be attracted to the Source magnet (BUT do not attract it ! )!
A conditional magnet, formed from a piece of iron placed in a magnetic field, behaves like a magnet, only in relation to the Source magnet. But, if another piece of iron is placed next to this conditional magnet (piece of iron), then these two pieces of iron will behave in relation to each other, like ordinary two pieces of iron ! In other words, the first iron magnet, as it were, forgets that it is a magnet. ! It is only important that the thickness of the first piece of iron be quite noticeable (for my home magnets - at least 2 mm) and the transverse dimension - more than the size of the second piece of iron !
But the pole of the same name of a forcibly inserted magnet (this is no longer a simple piece of iron) will definitely move the same pole away from itself if there are no obstacles !
In textbooks on physics, and sometimes in solid works on physics, it is written that some idea of the intensity of the magnetic field and the change in this intensity in space can be obtained by pouring iron filings on a substrate sheet (cardboard, plastic, plywood, glass or any non-magnetic material) placed on a magnet. The sawdust will line up in chains in the directions of the changing intensity of the field, and the density of the lines of sawdust will correspond to the very intensity of this field.
So this is puredeception !!! It seems that it never occurred to anyone to conduct a real experiment and pour these sawdust !
The sawdust will gather in two dense piles. One bunch will form around the north pole of the magnet, and the other will form around its south pole. !
An interesting fact is that just in the middle between two piles (in Zerozone) in general NOT will no sawdust ! This experiment calls into question the existence of the notorious magneticlines of force , which must leave the north pole of the magnet and enter its south pole !
M. Faraday, to put it mildly, was wrong !
If there is a lot of sawdust, then as the distance from the magnet pole increases, the pile will decrease and thin out, which is an indicator of the weakening of the magnetic field intensity as the Receiver point moves away in space from the Source point on the magnet pole. The observed decrease in the intensity of the magnetic field, of course, does not depend on the presence or absence of sawdust on the experimental substrate. ! Reduction - objectively !
But the decrease in the density of the sawdust coating on the substrate can be explained by the presence of sawdust friction on the substrate (on cardboard, on glass, etc.). Friction does not allow the weakened attraction to move the filings to the pole of the magnet. And the farther from the pole, the less the force of attraction and, thus, the less sawdust will be able to approach the pole. But, if the substrate is shaken, then ALL sawdust will gather as close as possible to the nearest pole ! Visible inhomogeneous density of the sawdust coating will thus be leveled !
In the middle zone of the transverse sections of the magnet, two magnetic fields are algebraically added: northern and southern. The total field density between the poles is the result of algebraic addition of intensities from opposite fields. In the very middle section, the sum of these intensities will be exactly equal to zero (Zerouzon is formed). For this reason, there should be no sawdust in this section at all and they are real No!
As you move away from the middle of the magnet (from the Zerozone) towards the magnetic pole (any), the intensity of the magnetic field will increase, reaching a maximum at the pole itself. The gradient of the change in the middle intensity is many times higher than the gradient of the change in the outer intensity.
But, in any case, the sawdust will NEVER line up at least in the semblance of some kind of lines connecting the north pole of a magnet with its south pole. !
Physics operates with the term "magnetic flux ».
So, there is NOmagnetic flux !
After all " flow " means "unidirectional movement of material particles or parts" ! If these particles are magnetic, then the flow is considered to be magnetic.
There are, of course, also figurative phrases such as "a stream of words", "a stream of thoughts", "a stream of troubles" and similar phrases. But they have nothing to do with physical phenomena.
And in a real magnetic field, nothing moves anywhere. ! There is only a magnetic field, the intensity of which decreases with distance from the nearest pole of the Source magnet.
If the flow existed, then the mass of particles would constantly flow out of the mass of the magnet ! And over time, the mass of the original magnet would noticeably decrease ! However, practice does not support this. !
Since the existence of the notorious magnetic lines of force is not confirmed by practice, the term “magnetic flux ».
Physics, by the way, gives such an interpretation of the magnetic flux, which only confirms the impossibility of "magnetic flux" in nature:
« Magnetic flux"- a physical quantity equal to the flux density of field lines passing through an infinitely small area dS ... (Continuation of the interpretation can be viewed on the Internet).
Already from the beginning of the definition follows rubbish ! « Flow", it turns out that this is an ordered movement of "lines of force" that do not exist in Nature ! That in itself is already nonsense ! From lines it is impossible at all ( ! ) to form a “Flow”, since the line is NOT a material object (substance) ! And to form a stream from non-existing lines - all the more it is NOT possible !
What follows is an equally interesting post. ! It turns out that the totality of non-existent lines of force forms a certain "density". According to the principle: the more lines that do not exist in Nature are collected in a limited section, the denser the non-existent beam of non-existent lines becomes !
Finally, " Flow"- this, according to physicists, is a physical magnitude!
What is called - ARRIVED» !!!
I invite the Reader to think for himself and understand why, say, "dream" cannot be a physical quantity?
Even if " magnetic flux" existed, then in any case, "Movement" (and "Flow" is "Movement") can NOT be size! " The "value" can be some movement parameter, for example: "Speed" of the movement, "Acceleration" of the movement, but in no way, not the "Movement" itself !
Because just the term "magnetic flux”physics could not digest, physicists had to supplement this term somewhat. Now physicists have this - "Flux of magnetic induction " (although, due to illiteracy, it is often found simply "magnetic flux») !
Horseradish radish, of course, is not sweeter !
« Induction » is not a material substance ! Therefore, she can NOT form a stream ! « Induction" is just a foreign translation from the Russian term "guidance», « Transition from private to general» !
You can use the termMagnetic induction ", as the effect of a magnetic field, but the term "Flux of magnetic induction» !
In physics there is a termMagnetic flux density » !
But, thank God, it is difficult for physicists to define this concept ! And therefore they (physicists) - do not give it !
And, if a concept that does not mean anything has taken root in physics, like “magnetic flux density", which for some reason is mixed with the concept of"magnetic induction", then:
Magnetic flux density (actually NOT existing), it is more logical to consider not the number of lines of force that do not exist in Nature in a unit section perpendicular to any non-existing line of force, but attitude the number of sawdust found in a unit section of the magnetic field relative to the number of the same sawdust, taken as a unit, in the same unit section, but at the pole itself, if the considered sections are perpendicular tomagnetic field vector .
I propose instead of the meaningless term "Magnetic flux density» apply a more logical term that defines the force with which the Source of the magnetic field can act on the Receiver, - «Magnetic field intensity » !
This is something similar toThe strength of the electromagnetic field».
Of course, no one will ever measure these amounts of sawdust ! Yes, no one will ever need it !
In physics, the term "Magnetic induction » !
It is a vector quantity (i.e. "Magnetic induction" is a vector) and shows with what force and in what direction the magnetic field acts on a moving charge !
I immediately give a significant correction to the interpretation accepted in physics !
A magnetic field NOT valid on charge! Regardless of whether this charge moves or not !
The magnetic field of the Source interactswith magnetic field generated moving charge !
It turns out that "magnetic induction" is nothing but "force", pushing the conductor with current ! BUT "force", pushing a current-carrying conductor, is nothing more than"Magnetic induction» !
And in physics, the following message is proposed: “The direction from the south pole is taken for the positive direction of the magnetic induction vector S to the north pole N a magnetic needle freely positioned in a magnetic field.
And if the compass needle was not nearby ! Whereas?
Then I propose the following !
If the conductor with current is located in the zone of the northern magnetic field, then the vector comes from closest to the conductor point-Source at the north pole of the magnet and crosses the conductor.
If the conductor with current is in the zone of the southern magnetic field, then the vector proceeds from the Receiver point closest to the magnetic pole on the conductor to the nearest Source point on the south pole of the magnet.
In other words, in any case, the shortest distance from the conductor to the nearest pole is taken. Further, depending on this distance, the magnitude of the force of the direct effect of the magnetic field on the conductor is taken (best of all - from the experimental graph of the dependence of the magnetic force on the distance).
I propose to perceive the described shortest distance as “Magnetic field vector ».
Thus, it turns out that the magnetic fields around one magnet (and, accordingly, the number of magnetic field vectors) can be identified as an unlimited set ! As many as you can build normals to the surfaces of the magnetic poles.
Properties of permanent magnets. 1. Opposite magnetic poles attract, like ones repel. 2. Magnetic lines are closed lines. Outside the magnet, the magnetic lines leave "N" and enter "S", closing inside the magnet. In 1600 English physician G.H. Gilbert deduced the basic properties of permanent magnets.
Slide 9 from the presentation "Permanent Magnets, Earth's Magnetic Field". The size of the archive with the presentation is 2149 KB.Physics Grade 8
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Christmas Eve. Evening before Christmas. Busy, but peaceful at the same time. An evening to be spent with family. An evening in which a miracle is expected.
Sasha narrowed his eyes, wincing at the prickly snowflakes. In the light of street lamps, the snow seemed much more magically silvery than in the rays of the sun. I wish he didn't get so in the eye ... Miron pulled the scarf higher, and pushed his hat over his eyebrows. Pretty cool, it's good that there is no wind.
This evening it is customary to be in the family circle - Sasha knew this very well. But - alas - not today, definitely. Now, when the anger has cooled down, and the nerves have calmed down, a misunderstanding has come - how could one quarrel with everyone at once? At first, having quarreled to the core with the Kaimanovs, Sasha wanted to go to his room, but at the door he ran into Teya. Excited, he threw some kind of barb, thereby angering his girlfriend. And then Dan got under the hot hand. And now what? Sasha walks alone through the almost deserted streets, scolding himself for going crazy and leaving. Yes, even the evening before Christmas. It didn't work out well.
"I'll be back later, when everyone is asleep," Miron decided to himself and, having cleared the bench of snow, sat down on its edge.
And the snow kept falling. Slow, easy. A typical windless winter evening. It would seem, how is Christmas Eve different from other winter evenings? A year has already passed, and miracles do not happen. Unless there are various surprises, both pleasant and not.
Myron seemed to wake up from a dream. He did not have time to come to his senses, as someone's cold little hands first touched his cheeks, and then thin arms wrapped around his neck.
Rakuri?!
Sasha rubbed his eyes and looked again. He just couldn't believe his eyes. This is the same girl with whom he happened to take a walk in the fresh green park in the summer ... And she hasn't even changed! A sweet round face, red-brown eyes, a light, almost weightless body. Even the clothes are the same - a red dress and black sandals.
It's cold! Sasha was outraged.
I do not feel cold. I'm used to it," Rakuri shrugged.
I do not believe...
Well, don't believe it. Why are you sitting here alone? Did you go to the store again?
Sasha laughed.
It's too late to go for bread! I'm walking ... Why are you here, and even undressed ?!
I promised to return.
Myron looked at her closely. Indeed, she promised. And returned. But it feels like she knew exactly where to look for Sasha, and that he would be alone.
But I won’t feed you anymore, I don’t have any money with me at all, - Sasha smiled sadly, spreading his arms.
Do not need. Rakuri placed her hands on his broad shoulders. You showed me your world, now I want to show mine.
Rakuri took Myron's hand and, taking steps back, forced her to stand up and follow her. Sasha hesitated a little, not knowing whether to do it, but still decided to go.
How do you not freeze? Sasha asked, perplexed, following the girl.
When we come to my world, you yourself will understand, - why Rakuri said with a slight sadness. - I'll introduce you to someone else.
Then they walked in silence. Sasha just didn't know what to talk about. The appearance of Rakuri was not just unexpected - it stunned. He did not expect to meet her at all, it seemed to him that after a summer walk she would never appear again. But here it is - quite real, material. Only the hands are very cold. Although, is it any wonder, it's so cold outside. In the end, Sasha couldn't help but wrap his scarf around Rakuri's neck. She looked around in surprise and stopped.
I'm cold to look at you. You will also get sick in addition, - grumbled Sasha.
Seriously, I'm telling you - I won't get sick, - Rakuri smiled in response and went on.
Myron shook his head, and suddenly noticed that all the buildings had disappeared somewhere, and instead of them an unfamiliar icy void appeared, only the snow was still slowly falling from the sky. Around only snowdrifts and bare trees, and somewhere in the distance - black rocks, looking to the sky. Sasha tightened his grip on Rakuri's hand, looking around restlessly.
What kind of place is it?!
We are already in my world,” Rakuri said calmly. “I’m sorry, there is no cafe like in your world, so I can’t treat you. How to do when inviting guests.
Rakuri slowly walked along the snow creaking under her feet, not letting go of Sasha's hand. He tightly squeezed her miniature palm, and with the other hand carefully grabbed her shoulders because it was quite difficult to go down these snowdrifts and not fall. And so they walked for about half an hour until they reached the foot of the mountains. Myron narrowed his eyes, trying to see what was there. He saw several caves, the entrances to which were hung with thick but tattered cloth. My heart beat restlessly - someone lives there, and not one or two people. However, do people live here?
Do not worry. As long as you are next to me, no one will touch you, - Rakuri said encouragingly and led Myron into one of the caves.
Who is it?! - immediately a thick and menacing voice was heard.
Sasha staggered back at this unexpected exclamation. The first thing that caught his eye was a woman dressed in a dress with blond hair gathered in a ponytail and scarlet eyes, and a scabbard with a two-handed sword on her shoulder. Moreover, she turned out to be quite tall and muscular, which surprised Sasha, who was used to short people because of her two-meter height. She walked over to Myron and Rakuri with long strides and, bending down, stared at the face of a stranger.
Valerie, stop it, - Rakuri said in a calm, even cold voice. - His name is Sasha. It was I who brought him.
This time, his owner turned out to be a short, pretty guy, although, at first glance, it seemed to Sasha that this was a girl. The guy sat on the floor and fiddled with his white and surprisingly long hair, on which the veil was fastened with rose hairpins. He got up from the floor and walked closer to get a better look at Sasha.
Isadel! Valerie yelled at the boy.
Don't yell at me," he replied calmly.
While they were sorting out among themselves, Myron looked around the cave, which he immediately failed to do. All of a sudden, it felt comfortable here, but in its own way. Books, old kerosene stoves, shabby toys and some strange rubbish are scattered everywhere. And it looks like the cave has been built for a long time.
Do not pay attention. I don't often take guests," Rakuri said.
And then Sasha felt some movement from behind, so turning around, he was preparing to defend himself, but instead of the expected danger, a small, tender, gray-eyed girl appeared in front of him, taller than Rakuri, but just as fragile and thin, with curly lavender hair, dressed in a dress not to size. The girl closed her eyes in surprise, not understanding who she sees in front of her.
Well... I'm Sasha, - Miron tried to introduce himself, but scared the girl a little with his chesty and hoarse voice.
Oh redhead! The girl giggled playfully. - I'm Loralei!
Get away from him! He is not from our world! came another voice.
Sasha saw approaching a short, but menacing woman dressed in a dress with sharp features and long, below the waist, hair. Already from afar it was clear how she sparkles with her evil yellow eyes. Approaching, the woman gave Myron a contemptuous look, and then, with an annoyed look at Rakuri, she disappeared into a nearby cave. Sasha did not even understand what the woman wanted to say.
This is Remilia. She's always like that," Rakuri explained. - This is where I live. With them. But you haven't seen them all yet.
Do not need! - Valerie snorted and, abruptly turning around, went further into the cave.
Sasha looked at Isadel and Loralei. The guy fiddled with his hair and carefully examined Miron from head to toe with his intelligent piercing gaze, and the girl smiled carelessly. Everything was so chaotic, unnatural and strange that even his head was spinning, and Sasha leaned on Rakuri's shoulder, as if this could save him from falling.
Went. You've seen enough, - she said and led Sasha by the hand out of the cave.
Myron took a deep breath of fresh frosty air. He could not collect his thoughts and understand where he was. They moved quite far from the caves, and the heart continued to beat rapidly. Sasha couldn't calm down.
You know, I think I should confess to you," Rakuri said slowly. - You will laugh, but I created this world.
Are you a goddess?
I am Diva. And everyone you saw is also a Diva. Yes... I am a goddess.
Sasha looked at the light, weightless figure of Rakuri and tried to understand how she could be the one who creates the worlds. No, it doesn't fit in my head at all. This girl cannot be the creator of worlds.
You do not believe me? Rakuri asked.
How can I believe it so easily? Sasha threw up his hands. - Okay, you brought me into this world, introduced me to strange people... But I can't just believe that you created all this... So you're not cold?
Not at all... Look away.
Look away.
Myron shrugged, but turned away anyway. And in just a couple of seconds, someone's big hands lay on his shoulders. Sasha almost jumped in surprise and turned around. Rakuri disappeared somewhere, but instead of her stood an unusually tall woman, about three heads taller than Myron, with black, resinous long hair. Only after looking closely Sasha realized that this woman had the face of that little girl with whom he came into this world.
Rakuri?! Myron exclaimed.
Yes, it's me." She tilted her head to the side. Trust me, I'm not human.
You are so... tall...
You must be uncomfortable.
Rakuri stepped closer. She breathed loudly and raggedly, worried. Her wide palm rested on Sasha's shoulder, and the other Rakuri touched his red hair. Myron looked up at her and was silent. Slowly and hesitantly, he touched her hand on his shoulder.
"So cold ..." - flashed through Sasha's head.
It's always ice cold here. We are all cold too. And inside - empty, - said Rakuri. - In fact, I'm not at all what you want me to be. You and I are like two poles - completely different.
Funny. Opposite poles attract, - Sasha smiled. - It can't be that you're empty inside. I do not think so.
You can think as you like, but this will not change my essence.
Myron looked into her cold, calm eyes and smiled warmly. After the shapeshifting, the scarf didn't disappear from Rakuri's neck. Therefore, she did not seem cold and empty to Sasha. The scarf made her more alive. More native.
You are a stupid little girl. How can you say that? Everyone can change. An empty glass can be filled with wonderful wine, - Sasha said affectionately.
Rakuri abruptly pulled away and in an instant returned to her normal form. Her face became sad and a little scared. Little drops of tears rolled from the scarlet eyes. Sasha sat down next to him and extended his arms to hug, but Rakuri pulled away, but this did not stop Miron from making another attempt and still enclosing Rakuri in his arms. But she did not burst into tears, the tears quickly dried on her cold face. Rakuri clasped Sasha's jacket on his back with her small hands and buried her face in his shoulder. But she didn't cry, she didn't even sob.
You are good, Sasha. And I am none. Neither bad nor good. I'm just a Diva, - said Rakuri, pushing Myron away from him. - It's time for you to go home.
Really...
Sasha stood up abruptly and looked around. Literally a few meters away from him, four people were standing with Rakuri. Very tall people, hardly any of them Sasha reaches the shoulder. One of them - a white-haired guy - looks menacingly, an uncontrollable flame splashes in his red eyes. And how he is not cold in some pants with suspenders is not clear. The tallest of them is a woman. Her face and hands are disfigured by scars, one eye is covered with a bandage, and the other - bluish-crystal - looks wary. Shaking her shock of unwashed dark hair, the woman now and then wraps her cloak around her. Next to her is a fair-haired girl, also in a raincoat and pants, she looks more benevolent than the other two.
The guy's name is Dick, that woman with scars is Rachel, and she's Yoko, - Rakuri immediately listed everyone, getting up from the snow.
Who is this person? Rachel asked.
Sasha, - calmly answered her.
Is he a Diva?
Dick looked at Sasha very attentively, appraisingly, but quickly looked away. Myron knows how to make no less formidable eyes. Yoko approached him and, looking intently into his eyes, smiled, thus forcing Sasha to answer in kind.
It's time for you to go home," Rakuri reminded her. - They'll take you.
Yes, so that we ...! Dick was about to shout, but he was interrupted.
I said: carry out!
Dick had to shut up, but he sniffed viciously anyway. Youko held out her hand to Sasha, and Rachel just chuckled.
And you? Sasha got worried.
And I stay at home. Hold the scarf...
Keep it.
Myron restrained himself so as not to cry. It became terribly sad. Why does she not want to see him off, but trusts it to those whom Sasha sees for the first time? ..
My kids won't do anything to you. See you. That was the last thing Sasha heard before Rakuri suddenly disappeared.
Went. We will see you off,” Youko said with a smile.
Myron had no choice but to follow them. The path he was being led was not at all like the one he and Rakuri had taken to reach the cliffs. Sasha trailed behind the trio, looking at their broad backs. Why did she call them her children? That is what Miron asked them.
She created us. She created everything here,” Rachel said.
Because she's a Diva? Sasha asked.
Because she is a goddess.
"So after all, you are a goddess. I was not mistaken," thought Sasha.
He was no longer surprised that Rachel, Yoko and Dick were gone, and buildings and roads appeared instead of an icy void. It's snowing here too. Prickly sparkling snow.
"Why didn't you promise to come back, fool? Although, no, she said "see you later," Miron thought frustrated. "You're not empty at all. You're good."
After standing for a minute in thought, Sasha went home. There he must have been waiting. After all, it's Christmas, you have to be with your family.
There are two different types of magnets. Some are the so-called permanent magnets, made from "hard magnetic" materials. Their magnetic properties are not related to the use of external sources or currents. Another type includes the so-called electromagnets with a core of "soft magnetic" iron. The magnetic fields created by them are mainly due to the fact that an electric current passes through the wire of the winding covering the core.
Magnetic poles and magnetic field.
The magnetic properties of a bar magnet are most noticeable near its ends. If such a magnet is suspended from the middle part so that it can freely rotate in a horizontal plane, then it will take a position approximately corresponding to the direction from north to south. The end of the rod pointing north is called the north pole, and the opposite end is called the south pole. Opposite poles of two magnets attract each other, while like poles repel each other.
If a bar of unmagnetized iron is brought near one of the poles of a magnet, the latter will temporarily become magnetized. In this case, the pole of the magnetized bar closest to the pole of the magnet will be opposite in name, and the far one will be of the same name. The attraction between the pole of the magnet and the opposite pole induced by it in the bar explains the action of the magnet. Some materials (such as steel) themselves become weak permanent magnets after being near a permanent magnet or electromagnet. A steel rod can be magnetized by simply passing the end of a permanent magnet across its end.
So, the magnet attracts other magnets and objects made of magnetic materials without being in contact with them. Such an action at a distance is explained by the existence of a magnetic field in the space around the magnet. Some idea of the intensity and direction of this magnetic field can be obtained by pouring iron filings on a sheet of cardboard or glass placed on a magnet. The sawdust will line up in chains in the direction of the field, and the density of the sawdust lines will correspond to the intensity of this field. (They are thickest at the ends of the magnet, where the intensity of the magnetic field is greatest.)
M. Faraday (1791–1867) introduced the concept of closed induction lines for magnets. The lines of induction exit the magnet at its north pole into the surrounding space, enter the magnet at the south pole, and pass inside the material of the magnet from the south pole back to the north, forming a closed loop. The total number of lines of induction coming out of a magnet is called magnetic flux. Magnetic flux density, or magnetic induction ( AT) is equal to the number of lines of induction passing along the normal through an elementary area of unit size.
Magnetic induction determines the force with which a magnetic field acts on a current-carrying conductor located in it. If the conductor carrying the current I, is located perpendicular to the lines of induction, then according to Ampère's law, the force F, acting on the conductor, is perpendicular to both the field and the conductor and is proportional to the magnetic induction, the current strength and the length of the conductor. Thus, for magnetic induction B you can write an expression
where F is the force in newtons, I- current in amperes, l- length in meters. The unit of measurement for magnetic induction is tesla (T).
Galvanometer.
A galvanometer is a sensitive device for measuring weak currents. The galvanometer uses the torque generated by the interaction of a horseshoe-shaped permanent magnet with a small current-carrying coil (weak electromagnet) suspended in the gap between the poles of the magnet. The torque, and hence the deflection of the coil, is proportional to the current and the total magnetic induction in the air gap, so that the scale of the instrument is almost linear with small deflections of the coil.
Magnetizing force and magnetic field strength.
Next, one more quantity should be introduced that characterizes the magnetic effect of the electric current. Let us assume that the current passes through the wire of a long coil, inside of which the magnetizable material is located. The magnetizing force is the product of the electric current in the coil and the number of its turns (this force is measured in amperes, since the number of turns is a dimensionless quantity). Magnetic field strength H equal to the magnetizing force per unit length of the coil. Thus, the value H measured in amperes per meter; it determines the magnetization acquired by the material inside the coil.
In a vacuum magnetic induction B proportional to the magnetic field strength H:
where m 0 - so-called. magnetic constant having a universal value of 4 p Ch 10 –7 H/m. In many materials, the value B approximately proportional H. However, in ferromagnetic materials, the ratio between B and H somewhat more complicated (which will be discussed below).
On fig. 1 shows a simple electromagnet designed to capture loads. The energy source is a DC battery. The figure also shows the lines of force of the field of an electromagnet, which can be detected by the usual method of iron filings.
Large electromagnets with iron cores and a very large number of ampere-turns, operating in continuous mode, have a large magnetizing force. They create a magnetic induction up to 6 T in the gap between the poles; this induction is limited only by mechanical stresses, heating of the coils and magnetic saturation of the core. A number of giant electromagnets (without a core) with water cooling, as well as installations for creating pulsed magnetic fields, were designed by P.L. Massachusetts Institute of Technology. On such magnets it was possible to achieve induction up to 50 T. A relatively small electromagnet, producing fields up to 6.2 T, consuming 15 kW of electrical power and cooled by liquid hydrogen, was developed at the Losalamos National Laboratory. Similar fields are obtained at cryogenic temperatures.
Magnetic permeability and its role in magnetism.
Magnetic permeability m is a value that characterizes the magnetic properties of the material. Ferromagnetic metals Fe, Ni, Co and their alloys have very high maximum permeabilities - from 5000 (for Fe) to 800,000 (for supermalloy). In such materials at relatively low field strengths H large inductions occur B, but the relationship between these quantities is, generally speaking, non-linear due to saturation and hysteresis phenomena, which are discussed below. Ferromagnetic materials are strongly attracted by magnets. They lose their magnetic properties at temperatures above the Curie point (770°C for Fe, 358°C for Ni, 1120°C for Co) and behave like paramagnets, for which induction B up to very high tension values H is proportional to it - exactly the same as it takes place in a vacuum. Many elements and compounds are paramagnetic at all temperatures. Paramagnetic substances are characterized by being magnetized in an external magnetic field; if this field is turned off, the paramagnets return to the non-magnetized state. The magnetization in ferromagnets is preserved even after the external field is turned off.
On fig. 2 shows a typical hysteresis loop for a magnetically hard (high loss) ferromagnetic material. It characterizes the ambiguous dependence of the magnetization of a magnetically ordered material on the strength of the magnetizing field. With an increase in the magnetic field strength from the initial (zero) point ( 1 ) magnetization goes along the dashed line 1 –2 , and the value m changes significantly as the magnetization of the sample increases. At the point 2 saturation is reached, i.e. with a further increase in the intensity, the magnetization no longer increases. If we now gradually decrease the value H to zero, then the curve B(H) no longer follows the same path, but passes through the point 3 , revealing, as it were, the "memory" of the material about the "past history", hence the name "hysteresis". Obviously, in this case, some residual magnetization is retained (the segment 1 –3 ). After changing the direction of the magnetizing field to the opposite, the curve AT (H) passes the point 4 , and the segment ( 1 )–(4 ) corresponds to the coercive force that prevents demagnetization. Further growth of values (- H) leads the hysteresis curve to the third quadrant - the section 4 –5 . The subsequent decrease in the value (- H) to zero and then increasing positive values H will close the hysteresis loop through the points 6 , 7 and 2 .
Magnetically hard materials are characterized by a wide hysteresis loop covering a significant area on the diagram and therefore corresponding to large values of residual magnetization (magnetic induction) and coercive force. A narrow hysteresis loop (Fig. 3) is characteristic of soft magnetic materials such as mild steel and special alloys with high magnetic permeability. Such alloys were created in order to reduce energy losses due to hysteresis. Most of these special alloys, like ferrites, have a high electrical resistance, which reduces not only magnetic losses, but also electrical losses due to eddy currents.
Magnetic materials with high permeability are produced by annealing carried out at a temperature of about 1000 ° C, followed by tempering (gradual cooling) to room temperature. In this case, preliminary mechanical and thermal treatment, as well as the absence of impurities in the sample, are very significant. For transformer cores at the beginning of the 20th century. silicon steels were developed, the value m which increased with increasing silicon content. Between 1915 and 1920, permalloys (alloys of Ni with Fe) appeared with their characteristic narrow and almost rectangular hysteresis loop. Particularly high values of magnetic permeability m for small values H hypernic (50% Ni, 50% Fe) and mu-metal (75% Ni, 18% Fe, 5% Cu, 2% Cr) alloys differ, while in perminvar (45% Ni, 30% Fe, 25% Co ) value m practically constant over a wide range of field strength changes. Among modern magnetic materials, we should mention supermalloy, an alloy with the highest magnetic permeability (it contains 79% Ni, 15% Fe, and 5% Mo).
Theories of magnetism.
For the first time, the idea that magnetic phenomena are ultimately reduced to electrical ones arose from Ampère in 1825, when he expressed the idea of closed internal microcurrents circulating in each atom of a magnet. However, without any experimental confirmation of the presence of such currents in matter (the electron was discovered by J. Thomson only in 1897, and the description of the structure of the atom was given by Rutherford and Bohr in 1913), this theory “faded”. In 1852, W. Weber suggested that each atom of a magnetic substance is a tiny magnet, or a magnetic dipole, so that the complete magnetization of a substance is achieved when all individual atomic magnets are lined up in a certain order (Fig. 4, b). Weber believed that molecular or atomic "friction" helps these elementary magnets to maintain their ordering despite the perturbing influence of thermal vibrations. His theory was able to explain the magnetization of bodies upon contact with a magnet, as well as their demagnetization upon impact or heating; finally, the “multiplication” of magnets was also explained when a magnetized needle or magnetic rod was cut into pieces. And yet this theory did not explain either the origin of the elementary magnets themselves, or the phenomena of saturation and hysteresis. Weber's theory was improved in 1890 by J. Ewing, who replaced his hypothesis of atomic friction with the idea of interatomic confining forces that help maintain the ordering of the elementary dipoles that make up a permanent magnet.
The approach to the problem, once proposed by Ampere, received a second life in 1905, when P. Langevin explained the behavior of paramagnetic materials by attributing to each atom an internal uncompensated electron current. According to Langevin, it is these currents that form tiny magnets, randomly oriented when the external field is absent, but acquiring an ordered orientation after its application. In this case, the approximation to complete ordering corresponds to saturation of the magnetization. In addition, Langevin introduced the concept of a magnetic moment, which for a single atomic magnet is equal to the product of the "magnetic charge" of the pole and the distance between the poles. Thus, the weak magnetism of paramagnetic materials is due to the total magnetic moment created by uncompensated electron currents.
In 1907, P. Weiss introduced the concept of "domain", which became an important contribution to the modern theory of magnetism. Weiss imagined domains as small "colonies" of atoms, within which the magnetic moments of all atoms, for some reason, are forced to maintain the same orientation, so that each domain is magnetized to saturation. A separate domain can have linear dimensions of the order of 0.01 mm and, accordingly, a volume of the order of 10–6 mm 3 . The domains are separated by the so-called Bloch walls, the thickness of which does not exceed 1000 atomic dimensions. The “wall” and two oppositely oriented domains are shown schematically in Fig. 5. Such walls are "transition layers" in which the direction of the domain magnetization changes.
In the general case, three sections can be distinguished on the initial magnetization curve (Fig. 6). In the initial section, the wall, under the action of an external field, moves through the thickness of the substance until it encounters a crystal lattice defect, which stops it. By increasing the field strength, the wall can be forced to move further through the middle section between the dashed lines. If after that the field strength is again reduced to zero, then the walls will no longer return to their original position, so that the sample will remain partially magnetized. This explains the hysteresis of the magnet. At the end of the curve, the process ends with the saturation of the sample magnetization due to the ordering of the magnetization within the last disordered domains. This process is almost completely reversible. Magnetic hardness is exhibited by those materials in which the atomic lattice contains many defects that prevent the movement of interdomain walls. This can be achieved by mechanical and thermal processing, for example by compressing and then sintering the powdered material. In alnico alloys and their analogues, the same result is achieved by fusing metals into a complex structure.
In addition to paramagnetic and ferromagnetic materials, there are materials with so-called antiferromagnetic and ferrimagnetic properties. The difference between these types of magnetism is illustrated in Fig. 7. Based on the concept of domains, paramagnetism can be considered as a phenomenon due to the presence in the material of small groups of magnetic dipoles, in which individual dipoles interact very weakly with each other (or do not interact at all) and therefore, in the absence of an external field, they take only random orientations ( Fig. 7, a). In ferromagnetic materials, within each domain, there is a strong interaction between individual dipoles, leading to their ordered parallel alignment (Fig. 7, b). In antiferromagnetic materials, on the contrary, the interaction between individual dipoles leads to their antiparallel ordered alignment, so that the total magnetic moment of each domain is zero (Fig. 7, in). Finally, in ferrimagnetic materials (for example, ferrites) there is both parallel and antiparallel ordering (Fig. 7, G), resulting in weak magnetism.
There are two convincing experimental confirmations of the existence of domains. The first of them is the so-called Barkhausen effect, the second is the powder figure method. In 1919, G. Barkhausen established that when an external field is applied to a sample of a ferromagnetic material, its magnetization changes in small discrete portions. From the point of view of the domain theory, this is nothing more than a jump-like advancement of the interdomain wall, which encounters individual defects that hold it back on its way. This effect is usually detected using a coil in which a ferromagnetic rod or wire is placed. If a strong magnet is alternately brought to the sample and removed from it, the sample will be magnetized and remagnetized. Jump-like changes in the magnetization of the sample change the magnetic flux through the coil, and an induction current is excited in it. The voltage that arises in this case in the coil is amplified and fed to the input of a pair of acoustic headphones. Clicks perceived through the headphones indicate an abrupt change in magnetization.
To reveal the domain structure of a magnet by the method of powder figures, a drop of a colloidal suspension of a ferromagnetic powder (usually Fe 3 O 4) is applied to a well-polished surface of a magnetized material. Powder particles settle mainly in places of maximum inhomogeneity of the magnetic field - at the boundaries of domains. Such a structure can be studied under a microscope. A method has also been proposed based on the passage of polarized light through a transparent ferromagnetic material.
Weiss's original theory of magnetism in its main features has retained its significance to the present day, however, having received an updated interpretation based on the concept of uncompensated electron spins as a factor determining atomic magnetism. The hypothesis of the existence of an intrinsic moment of an electron was put forward in 1926 by S. Goudsmit and J. Uhlenbeck, and at present it is electrons as spin carriers that are considered as “elementary magnets”.
To clarify this concept, consider (Fig. 8) a free atom of iron, a typical ferromagnetic material. Its two shells ( K and L), closest to the nucleus, are filled with electrons, with two on the first of them, and eight on the second. AT K-shell, the spin of one of the electrons is positive, and the other is negative. AT L-shell (more precisely, in its two subshells), four of the eight electrons have positive spins, and the other four have negative spins. In both cases, the spins of the electrons within the same shell cancel out completely, so that the total magnetic moment is zero. AT M-shell, the situation is different, because of the six electrons in the third subshell, five electrons have spins directed in one direction, and only the sixth - in the other. As a result, four uncompensated spins remain, which determines the magnetic properties of the iron atom. (In the outer N-shell has only two valence electrons, which do not contribute to the magnetism of the iron atom.) The magnetism of other ferromagnets, such as nickel and cobalt, is explained in a similar way. Since neighboring atoms in an iron sample strongly interact with each other, and their electrons are partially collectivized, this explanation should be considered only as an illustrative, but very simplified scheme of the real situation.
The theory of atomic magnetism, based on the electron spin, is supported by two interesting gyromagnetic experiments, one of which was carried out by A. Einstein and W. de Haas, and the other by S. Barnett. In the first of these experiments, a cylinder of ferromagnetic material was suspended as shown in Fig. 9. If a current is passed through the winding wire, then the cylinder rotates around its axis. When the direction of the current (and hence the magnetic field) changes, it turns in the opposite direction. In both cases, the rotation of the cylinder is due to the ordering of the electron spins. In Barnett's experiment, on the contrary, a suspended cylinder, sharply brought into a state of rotation, is magnetized in the absence of a magnetic field. This effect is explained by the fact that during the rotation of the magnet a gyroscopic moment is created, which tends to rotate the spin moments in the direction of its own axis of rotation.
For a more complete explanation of the nature and origin of short-range forces that order neighboring atomic magnets and counteract the disordering effect of thermal motion, one should turn to quantum mechanics. A quantum mechanical explanation of the nature of these forces was proposed in 1928 by W. Heisenberg, who postulated the existence of exchange interactions between neighboring atoms. Later, G. Bethe and J. Slater showed that the exchange forces increase significantly with decreasing distance between atoms, but after reaching a certain minimum interatomic distance, they drop to zero.
MAGNETIC PROPERTIES OF SUBSTANCE
One of the first extensive and systematic studies of the magnetic properties of matter was undertaken by P. Curie. He found that according to their magnetic properties, all substances can be divided into three classes. The first includes substances with pronounced magnetic properties, similar to those of iron. Such substances are called ferromagnetic; their magnetic field is noticeable at considerable distances ( cm. higher). Substances called paramagnetic fall into the second class; their magnetic properties are generally similar to those of ferromagnetic materials, but much weaker. For example, the force of attraction to the poles of a powerful electromagnet can pull an iron hammer out of your hands, and in order to detect the attraction of a paramagnetic substance to the same magnet, as a rule, very sensitive analytical balances are needed. The last, third class includes the so-called diamagnetic substances. They are repelled by an electromagnet, i.e. the force acting on diamagnets is directed opposite to that acting on ferro- and paramagnets.
Measurement of magnetic properties.
In the study of magnetic properties, measurements of two types are most important. The first of them is the measurement of the force acting on the sample near the magnet; this is how the magnetization of the sample is determined. The second includes measurements of "resonant" frequencies associated with the magnetization of matter. Atoms are tiny "gyroscopes" and in a magnetic field precess (like a normal spinning top under the influence of a torque created by gravity) at a frequency that can be measured. In addition, a force acts on free charged particles moving at right angles to the lines of magnetic induction, as well as on an electron current in a conductor. It causes the particle to move in a circular orbit, the radius of which is given by
R = mv/eB,
where m is the mass of the particle, v- her speed e is its charge, and B is the magnetic induction of the field. The frequency of such a circular motion is equal to
where f measured in hertz e- in pendants, m- in kilograms, B- in Tesla. This frequency characterizes the movement of charged particles in a substance in a magnetic field. Both types of motion (precession and motion in circular orbits) can be excited by alternating fields with resonant frequencies equal to the "natural" frequencies characteristic of a given material. In the first case, the resonance is called magnetic, and in the second, cyclotron (in view of the similarity with the cyclic motion of a subatomic particle in a cyclotron).
Speaking about the magnetic properties of atoms, it is necessary to pay special attention to their angular momentum. The magnetic field acts on a rotating atomic dipole, trying to rotate it and set it parallel to the field. Instead, the atom begins to precess around the direction of the field (Fig. 10) with a frequency depending on the dipole moment and the strength of the applied field.
The precession of atoms cannot be directly observed, since all the atoms of the sample precess in a different phase. If, however, a small alternating field directed perpendicular to the constant ordering field is applied, then a certain phase relationship is established between the precessing atoms, and their total magnetic moment begins to precess with a frequency equal to the frequency of the precession of individual magnetic moments. The angular velocity of precession is of great importance. As a rule, this value is of the order of 10 10 Hz/T for the magnetization associated with electrons, and of the order of 10 7 Hz/T for the magnetization associated with positive charges in the nuclei of atoms.
A schematic diagram of the installation for observing nuclear magnetic resonance (NMR) is shown in fig. 11. The substance under study is introduced into a uniform constant field between the poles. If an RF field is then excited with a small coil around the test tube, resonance can be achieved at a certain frequency, equal to the precession frequency of all the nuclear "gyroscopes" of the sample. Measurements are similar to tuning a radio receiver to the frequency of a particular station.
Magnetic resonance methods make it possible to study not only the magnetic properties of specific atoms and nuclei, but also the properties of their environment. The point is that magnetic fields in solids and molecules are inhomogeneous, since they are distorted by atomic charges, and the details of the course of the experimental resonance curve are determined by the local field in the region where the precessing nucleus is located. This makes it possible to study the features of the structure of a particular sample by resonance methods.
Calculation of magnetic properties.
The magnetic induction of the Earth's field is 0.5×10 -4 T, while the field between the poles of a strong electromagnet is of the order of 2 T or more.
The magnetic field created by any configuration of currents can be calculated using the Biot-Savart-Laplace formula for the magnetic induction of the field created by the current element. The calculation of the field created by contours of various shapes and cylindrical coils is in many cases very complicated. Below are formulas for a number of simple cases. Magnetic induction (in teslas) of the field created by a long straight wire with current I
The field of a magnetized iron rod is similar to the external field of a long solenoid with the number of ampere turns per unit length corresponding to the current in the atoms on the surface of the magnetized rod, since the currents inside the rod cancel each other out (Fig. 12). By the name of Ampere, such a surface current is called Ampère. Magnetic field strength H a, created by the Ampere current, is equal to the magnetic moment of the unit volume of the rod M.
If an iron rod is inserted into the solenoid, then in addition to the fact that the solenoid current creates a magnetic field H, the ordering of atomic dipoles in the magnetized material of the rod creates magnetization M. In this case, the total magnetic flux is determined by the sum of the real and ampere currents, so that B = m 0(H + H a), or B = m 0(H+M). Attitude M/H called magnetic susceptibility and is denoted by the Greek letter c; c is a dimensionless quantity characterizing the ability of a material to be magnetized in a magnetic field.
Value B/H, which characterizes the magnetic properties of the material, is called the magnetic permeability and is denoted by m a, and m a = m 0m, where m a is absolute, and m- relative permeability,
In ferromagnetic substances, the value c can have very large values - up to 10 4 ё 10 6 . Value c paramagnetic materials have a little more than zero, and diamagnetic materials have a little less. Only in vacuum and in very weak fields are the quantities c and m are constant and do not depend on the external field. Dependency induction B from H is usually non-linear, and its graphs, the so-called. magnetization curves for different materials and even at different temperatures can differ significantly (examples of such curves are shown in Figs. 2 and 3).
The magnetic properties of matter are very complex, and a thorough understanding of their structure requires a thorough analysis of the structure of atoms, their interactions in molecules, their collisions in gases, and their mutual influence in solids and liquids; the magnetic properties of liquids are still the least studied.
At home, at work, in our own car or in public transport, we are surrounded by various types of magnets. They power motors, sensors, microphones, and many other common things. At the same time, in each area, devices that are different in their characteristics and features are used. In general, these types of magnets are distinguished:
What are magnets
Electromagnets. The design of such products consists of an iron core, on which coils of wire are wound. By applying an electric current with different parameters of magnitude and direction, it is possible to obtain magnetic fields of the desired strength and polarity.
The name of this group of magnets is an abbreviation of the names of its components: aluminum, nickel and cobalt. The main advantage of alnico alloy is the unsurpassed temperature stability of the material. Other types of magnets cannot boast of being able to be used at temperatures up to +550 ⁰ C. At the same time, this lightweight material is characterized by a weak coercive force. This means that it can be completely demagnetized when exposed to a strong external magnetic field. At the same time, due to its affordable price, alnico is an indispensable solution in many scientific and industrial sectors.
Modern magnetic products
So, we figured out the alloys. Now let's move on to what magnets are and what application they can find in everyday life. In fact, there is a huge variety of options for such products:
3) office magnets. For presentations and meetings, magnetic boards are used, which allow you to present any information visually and in detail. They are also extremely useful in school classrooms and university classrooms.
