Permanent magnets
One of the most amazing natural phenomena is the manifestation of magnetism in some materials. Permanent magnets have been known since ancient times. Before the great discoveries in the field of electricity, permanent magnets were actively used by doctors of different nations in medicine. People got them from the bowels of the earth in the form of pieces of magnetic iron ore. Over time, people learned to create artificial magnets by placing products made from iron alloys near natural sources of magnetic fields.
The nature of magnetism
The demonstration of the properties of a magnet in attracting metal objects to itself raises the question among people: what are permanent magnets? What is the nature of such a phenomenon as the occurrence of traction of metal objects towards magnetite?
The first explanation of the nature of magnetism was given in his hypothesis by the great scientist Ampere. Electric currents of varying degrees of strength flow in any matter. Otherwise they are called Ampere currents. Electrons, rotating around their own axis, also revolve around the nucleus of the atom. Thanks to this, elementary magnetic fields arise, which, interacting with each other, form the general field of matter.
In potential magnetites, in the absence of external influence, the fields of the atomic lattice elements are randomly oriented. An external magnetic field “arranges” the microfields of the material structure in a strictly defined direction. The potentials of opposite ends of magnetite repel each other. If you bring the identical poles of two strip PMs closer, then a person’s hands will feel resistance to movement. Different poles will tend to each other.
When steel or an iron alloy is placed in an external magnetic field, the internal fields of the metal are strictly oriented in one direction. As a result, the material acquires the properties of a permanent magnet (PM).
How to see a magnetic field
To visually sense the structure of the magnetic field, it is enough to conduct a simple experiment. To do this, take two magnets and small metal shavings.
Important! In everyday life, permanent magnets are found in two forms: in the form of a straight strip and a horseshoe.
Having covered the strip PM with a sheet of paper, iron filings are poured onto it. The particles instantly line up along the magnetic field lines, which gives a clear idea of this phenomenon.
Demonstration of the magnetic field structure
Types of magnets
What is the source of the magnetic field
Permanent magnets are divided into 2 types:
- natural;
- artificial.
Natural
In nature, a natural permanent magnet is a fossil in the form of a fragment of iron ore. Magnetic rock (magnetite) has its own name in every nation. But in each name there is such a concept as “loving”, “attracting metal”.
The name Magnitogorsk means the city's location next to mountain deposits of natural magnetite. For many decades, active mining of magnetic ore was carried out here. Today there is nothing left of Magnetic Mountain.
This was the development and extraction of natural magnetite.
Until humanity achieved the proper level of scientific and technological progress, natural permanent magnets served for various fun and tricks.
Artificial
Artificial PMs are obtained by inducing an external magnetic field on various metals and their alloys. It was noticed that some materials retain the acquired field for a long time - they are called solid magnets. Materials that quickly lose the properties of permanent magnets are called soft magnets.
In factory production conditions, complex metal alloys are used. The structure of the Magnico alloy includes iron, nickel and cobalt. Alnico alloy contains aluminum instead of iron.
Products made from these alloys interact with powerful electromagnetic fields. As a result, quite powerful PMs are obtained.
Application of permanent magnets
PM is of no small importance in various areas of human activity. Depending on the scope of application, PMs have different characteristics. Recently, the actively used main magnetic alloy NdFeB consists of the following chemical elements:
- “Nd” – niodium,
- "Fe" - iron,
- "B" - boron.
Magnetic flux formula
Areas where permanent magnets are used:
- Ecology;
- Electroplating;
- Medicine;
- Transport;
- Computer techologies;
- Household appliances;
- Electrical engineering.
Ecology
Various industrial waste treatment systems have been developed and are in operation. Magnetic systems purify liquids during the production of ammonia, methanol and other substances. Magnetic collectors “select” all iron-containing particles from the flow.
Ring-shaped PMs are installed inside gas ducts, which rid gaseous exhausts of ferromagnetic inclusions.
Separator magnetic traps actively select metal-containing waste on conveyor lines for processing industrial waste.
Electroplating
Electroplating is based on the movement of charged metal ions to opposite poles of direct current electrodes. PMs play the role of product holders in the galvanic pool. In industrial installations with galvanic processes, only magnets made of NdFeB alloy are installed.
Medicine
Recently, medical equipment manufacturers have been widely advertising instruments and devices based on permanent magnets. A constant intense field is provided by the characteristics of the NdFeB alloy.
The property of permanent magnets is used to normalize the circulatory system, extinguish inflammatory processes, restore cartilage tissue, etc.
Transport
Transport systems in production are equipped with PM installations. During the conveyor movement of raw materials, magnets remove unnecessary metallic inclusions from the array. Magnets are used to direct different products into different planes.
Note! Permanent magnets are used to separate materials where the presence of people may have a detrimental effect on their health.
Automobile transport is equipped with a mass of instruments, components and devices, where PMs play the main role. These are electronic ignition, automatic windows, idle control, gasoline and diesel pumps, front panel instruments and much more.
Computer techologies
All mobile devices and devices in computer technology are equipped with magnetic elements. The list includes printers, driver engines, drive motors and other devices.
Household appliances
These are mainly holders for small household items. Shelves with magnetic holders, fastenings for curtains and curtains, holders for a set of kitchen knives and a host of other household appliances.
Electrical engineering
Electrical engineering based on PM concerns such areas as radio devices, generators and electric motors.
Radio engineering
PM is used to increase the compactness of radio engineering devices and ensure device autonomy.
Generators
PM generators solve the problem of moving contacts - rings with brushes. In traditional industrial devices, there are acute issues related to complex maintenance of equipment, rapid wear of parts, and significant loss of energy in excitation circuits.
The only obstacle to the creation of such generators is the problem of mounting the PM on a rotating rotor. Recently, magnets have been placed in the longitudinal grooves of the rotor, filled with low-melting material.
Generator rotor and stator
Electric motors
In household appliances and in some industrial equipment, synchronous electric motors with permanent magnets have become widespread - these are DC valve motors.
As in the generators described above, the PM is installed on rotors rotating inside stators with a stationary winding. The main advantage of the electric motor is the absence of short-lived conductive contacts on the rotor commutator.
Permanent magnet motor
Engines of this type are low-power devices. However, this does not in any way diminish their usefulness in the field of electrical engineering.
Additional Information. A distinctive feature of the device is the presence of a Hall sensor that regulates the rotor speed.
The author hopes that after reading this article the reader will have a clear idea of what a permanent magnet is. The active introduction of permanent magnets into human activity stimulates the invention and creation of new ferromagnetic alloys with enhanced magnetic characteristics.
Source: https://amperof.ru/elektropribory/postoyannye-magnity.html
“Magnit” has captured Russia! The history of the creation and development of the most popular retail chain
The Magnit chain of stores is one of the most recognizable brands in the European part of Russia. The company, founded in the mid-nineties in Krasnodar, has expanded to 14 thousand stores over the years.
Reconomica magazine studied the history of the brand to understand what helped the provincial company achieve such scale.
How it all began
Sergey Galitsky, the founder of the network, began his business career as a distributor of perfumes, cosmetics and household chemicals in 1994. A year later, he stops cooperation with his partners and opens a new company, preferring to make decisions alone.
Galitsky's first stores were intended for wholesale buyers. Over time, the formats of retail outlets changed, gradually changing sales volumes and pricing policies.
The name “Magnit” itself appeared only in 2001. The production of goods for the chain is launched, but “Magnit” in its familiar form appears only in 2004, when Galitsky decides to open retail outlets in the “At Home” format.
The name “Magnit” itself appeared only in 2001.
Even then, the company showed its special policy of opening new points: instead of launching stores in the capitals, Galitsky focused on regional and regional centers.
10 thousand stores - this is exactly the level that Magnit crossed in 2010. In 2015, the company opened 7 stores per day. In 2019, the network’s staff is about 300 thousand people. In 2018, Galitsky sold most of his stake to VTB Bank.
Network Features
Of course, the huge growth rates cannot be an accident. There are several reasons that have accelerated the progress of the network.
Personality of the company president
Those involved in the creation and management of the brand say that the system of relationships between management and subordinates was similar to the army structure. Galitsky made decisions at various levels: from choosing the format of a new store in a small town to choosing a price tag on a particular product. And if in such situations the great influence of management can only slow down processes, then Magnit did not have any problems with this.
In 2019, the network’s staff is about 300 thousand people.
Special attention to small towns
Over the years, Galitsky has been asked whether he is afraid of competition in Moscow and St. Petersburg. Many journalists believed that this was the reason why Magnit opened primarily in the provinces. But the reason, obviously, was not fear of competition.
Source: https://reconomica.ru/%D1%8D%D0%BA%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D0%BA%D0%B0/%D0% B0%D0%BD%D0%B0%D0%BB%D0%B8%D1%82%D0%B8%D0%BA%D0%B0/%D0%B8%D1%81%D1%82%D0%BE %D1%80%D0%B8%D1%8F-%D0%BC%D0%B0%D0%B3%D0%BD%D0%B8%D1%82%D0%B0/
Neodymium magnet. History of invention. Where are they used?
The strongest and most powerful permanent magnet currently available for sale is the neodymium magnet. Such magnets have the chemical formula Nd2Fe14B, and have an exceptional magnetic energy density reaching 512 kJ/m3.
If previously samarium-cobalt (SmCo) magnets were considered the most powerful commercially available, then, starting in 1986, they were gradually replaced by neodymium magnets, which were much more economical in production costs, although with a lower Curie temperature.
With the development of the electronics industry, from the 90s to the present, neodymium magnets have gained great popularity everywhere, and many are still surprised by their remarkable properties, because such a magnet can lift a load thousands of times greater than the weight of the magnet itself.
Neodymium magnet
It all started when in 1982 the Japanese company Sumitomo Special Metals, working together with the American General Motors on the problem of finding an alternative to expensive samarium-cobalt (SmCo) magnets, found a neodymium-iron-boron compound, which was patented by General Motors in 1985 In 1986, the Magnequench company was opened, specializing in the production of neodymium magnets and selling raw materials for their manufacture.
Magnequench later became part of Molycorp, USA, and Sumitomo became part of Hitachi Corporation, Japan, and Hitachi now holds more than 600 patents related to the production of neodymium magnets by sintering and licenses numerous facilities around the world.
In the end, China became the leader in the production of neodymium magnets, because this country controls a huge share of the world's rare earth ores.
China produces 50,000 tons of neodymium magnets every year. Meanwhile, one ton of the original ore contains about 700 kg of iron, and neodymium - a maximum of 450 grams.
Neodymium
For the manufacture of neodymium magnets, powder technology is used, which makes it possible to produce three types of magnets: pressed magnets, cast magnets, and sintered magnets.
Before making magnets, magnetic material is smelted; for this, the initial elements (iron, neodymium, boron) are fused in an induction furnace, then the resulting alloy is crushed, obtaining powder for further stages of the technological process, for working with the powder.
Characteristics of magnets
Depending on the microstructure of the starting elements, the magnetic properties of the final product may vary to some extent. Often the Nd2Fe14B compound is used directly. It is its structure that gives the maximum magnetocrystalline, uniaxial anisotropy. But more complex chemical reactions are also possible.
Sintered magnetoplasts
They are obtained by pressing neodymium-iron-boron powder, sintering it in an inert or vacuum environment, and then grinding it on a machine until the desired shape is obtained. During the pressing of the powder, it is acted upon by a magnetic field of the required intensity and direction, which sets the magnetization.
Cast magnets
They are obtained using polymers that are mixed with neodymium-iron-boron powder and then extruded into a mold, and here it is possible to obtain any shape, however, the energy of the product is limited to 5 MGE.
Pressed magnetoplasts
They are obtained as follows: the original neodymium-iron-boron powder is mixed with a polymer, then pressed into a shape, heated and magnetized. No additional processing is required, and the energy of pressed magnetoplasts is limited to 10 MGse.
Distinctive properties and technical characteristics
So, neodymium magnets have the following distinctive properties:
- Over 10 years, only 1% of magnetization is lost
- Any sizes and shapes available
- Low Curie temperature (see table above)
- High corrosion resistance
- Maximum remanence
- Maximum coercivity
- Maximum specific magnetic energy
Neodymium magnets are marked as follows, these are the so-called classes of neodymium magnets:
- N35-N52
- 33M-48M
- 30H-45H
- 30SH-42SH
- 30UH-35UH
- 28EH-35EH
Here the number denotes the magnetic energy expressed in MGse (MegaGauss-Oersted), and the letter (brand) is the permissible temperature range:
- N (Normal) – up to 80 degrees Celsius
- M (Medium) – up to 100 degrees Celsius
- H (High) – up to 120 degrees Celsius
- SH (Super High) – up to 150 degrees Celsius
- UH (Ultra High) – up to 180 degrees Celsius
- EH (Extra High) – up to 200 degrees Celsius
Usually, the seller is always ready to provide comprehensive information about the technical characteristics of the neodymium magnets he offers.
Scope of application of neodymium magnets
Neodymium magnets have almost completely replaced ferrite magnets in many applications, including industrial applications, as they are much stronger while being more compact.
Thus, neodymium magnets have found the following applications:
- in computer hard disk drives
- as part of erasing heads of inexpensive equipment
- in magnetic resonance imaging (MRI)
- in magnetic guitar pickups
- in electronic cigarettes
- in door locks
- in loudspeakers and headphones
- in magnetic bearings
- in NMR spectrometers
- in electric motors
- in cordless tools
- in servomotors
- in lifting and compressor engines
- in stepper motors
- in electric power steering
- on hybrid and electric vehicles
- in generators and turbines (direct drive turbines require 600 kg of magnets per megawatt of power, and 31% of this mass is neodymium)
Neodymium magnet toy
In addition, neodymium magnets with their unique magnetic properties have inspired the creators of toys and jewelry. Everyone knows the neocube magnetic kits and others; various construction sets, various decorative fasteners, etc.
Thus, neodymium magnets are capable of not only solving complex production problems, but also simple, convenient solutions.
Recently, powerful magnets have been actively promoted for use in illegal activities. The advertisement encourages you to buy magnets with which you can use electricity, heat and gas without accounting for the consumed resources with the corresponding meters. Unaccounted use of such resources is illegal, according to the Code of Administrative Offences.
See also on the topic:
Magnetic motor with permanent magnets. Minato engine.
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Source: https://powercoup.by/kak-eto-ustroeno/neodimovyiy-magnit
Commercial network
TASS DOSSIER. On February 16, 2018, at the Russian Investment Forum in Sochi, the founder, CEO and main owner of the Russian retail chain Magnit, Sergei Galitsky, entered into an agreement with VTB to sell the bank a controlling stake in the retailer - 29.1% of shares - for 138 billion rubles.
It is expected that in the near future the post of general director of Magnit will be taken by the chairman of the board of directors Khachatur Pombukhchan.
Magnit is one of the largest retail companies in Russia and Europe. As of the beginning of 2018, there were 16 thousand 350 stores under the management and brand of Magnit, including 243 hypermarkets. In total, the company operates in 2 thousand 665 cities of Russia.
The largest number of stores are opened in the Southern, North Caucasian, Volga and Central federal districts. The company has one of the largest transport and logistics networks in Russia.
Magnit ranks 1st among Russian retailers in terms of revenue (according to the InfoLine-Analytics company) and 7th in Russia among all Russian companies (according to the RBC-500 rating). Registered in Krasnodar.
Story
The founder of the company is entrepreneur Sergei Galitsky. In July 1995, together with his partner Alexei Bogachev, he created the Tander company (now a joint stock company, Tander JSC) and became its general director. Initially, the company was engaged in wholesale supplies of perfumes in the southern regions of Russia.
In 1998, the company opened the first retail supermarket "Magnit" in Krasnodar. Subsequently, stores were created in other cities, mainly in the south of Russia. Galitsky avoided competition with large retail chains by developing business in small towns and positioning his outlets as neighborhood stores with low prices.
In the early 2000s, they were united into a retail chain called Magnit.
In 2003, Galitsky registered Magnit OJSC (now PJSC), which received 100% of Tander shares.
In 2006, Magnit listed its shares on the stock exchange, and the construction of the chain’s hypermarkets began with the proceeds. Since 2010, the company has been developing a network of Magnit-Cosmetic retail stores. In its stores, Magnit sells a range of products of its own brands: “Family Secrets”, “Master Shine”, “Northern Harbor”, “Save Reasonably”, “Trading House Smetanin”, etc.
Indicators
At the end of the last reporting year of 2016, Magnit’s consolidated revenue according to international financial reporting standards amounted to 1 trillion 74 billion rubles. (an increase of 4.6% compared to 2015), net profit amounted to 1.14 billion rubles. (Before this, Magnit showed a net loss for the last three years).
According to Spark-Interfax, Magnit accounts for 25% of the revenue of all retail trade in the Russian Federation and 22% of the revenue of all companies registered in the Krasnodar Territory.
The number of personnel (as of September 30, 2017) is 289 thousand 366 people.
Management
Since 2006, Sergei Galitsky has been the general director of Magnit, and since 2010, also the chairman of the board. Chairman of the Board of Directors - Khachatur Pombukhchan.
Owners
At the end of the third quarter of 2017, Galitsky owned 35.11% of the company’s shares. The largest minority shareholder is the American investment company OppenheimerFunds Inc. More than 50% of the retailer's shares are traded on the open market. Current market capitalization is about $10 billion.
Official website - http://magnit-info.ru/.
Source: https://tass.ru/info/4965118
What is a magnet?
Magnet
Everyone held a magnet in their hands and played with it as a child. Magnets can be very different in shape and size, but all magnets have a common property - they attract iron. It seems that they themselves are made of iron, at least of some kind of metal for sure. There are, however, “black magnets” or “stones”; they also strongly attract pieces of iron, and especially each other.
But they don’t look like metal; they break easily, like glass. Magnets have many useful uses, for example, it is convenient to “pin” paper sheets to iron surfaces with their help. A magnet is convenient for collecting lost needles, so, as we can see, this is a completely useful thing.
Ancient China
Science 2.0 - Great Leap Forward - Magnets
Magnet in the past
More than 2000 years ago, the ancient Chinese knew about magnets, at least that this phenomenon could be used to choose a direction when traveling. That is, they invented a compass.
Philosophers in ancient Greece, curious people, collecting various amazing facts, encountered magnets in the vicinity of the city of Magnessa in Asia Minor. There they discovered strange stones that could attract iron.
At that time, this was no less amazing than aliens could become in our time.
It seemed even more surprising that magnets do not attract all metals, but only iron, and iron itself can become a magnet, although not so strong. We can say that the magnet attracted not only iron, but also the curiosity of scientists, and greatly moved forward such a science as physics.
Thales of Miletus wrote about the “soul of a magnet,” and the Roman Titus Lucretius Carus wrote about the “raging movement of iron filings and rings” in his essay “On the Nature of Things.”
He could already notice the presence of two poles of the magnet, which later, when sailors began to use the compass, were named after the cardinal points.
What is a magnet? In simple words. A magnetic field
We took the magnet seriously
The nature of magnets could not be explained for a long time. With the help of magnets, new continents were discovered (sailors still treat the compass with great respect), but no one still knew anything about the very nature of magnetism. Work was carried out only to improve the compass, which was also done by the geographer and navigator Christopher Columbus.
In 1820, the Danish scientist Hans Christian Oersted made a major discovery. He established the action of a wire with an electric current on a magnetic needle, and as a scientist, he found out through experiments how this happens under different conditions.
In the same year, the French physicist Henri Ampere came up with a hypothesis about elementary circular currents flowing in the molecules of magnetic matter.
In 1831, the Englishman Michael Faraday, using a coil of insulated wire and a magnet, conducted experiments showing that mechanical work can be converted into electric current. He also established the law of electromagnetic induction and introduced the concept of “magnetic field”.
Hans Christian Oersted
Faraday's law establishes the rule: for a closed loop, the electromotive force is equal to the rate of change of the magnetic flux passing through this loop. All electrical machines operate on this principle - generators, electric motors, transformers.
In 1873, Scottish scientist James C. Maxwell combines magnetic and electrical phenomena into one theory, classical electrodynamics.
Substances that can be magnetized are called ferromagnets. This name associates magnets with iron, but besides it, the ability to magnetize is also found in nickel, cobalt, and some other metals. Since the magnetic field has already entered the field of practical use, magnetic materials have become the subject of great attention.
Experiments began with alloys of magnetic metals and various additives in them.
The resulting materials were very expensive, and if Werner Siemens had not come up with the idea of replacing the magnet with steel magnetized by a relatively small current, the world would never have seen the electric tram and the Siemens company.
Siemens also worked on telegraph devices, but here he had many competitors, and the electric tram gave the company a lot of money, and ultimately pulled everything else along with it.
Electromagnetic induction
Basic quantities associated with magnets in technology
We will be interested mainly in magnets, that is, ferromagnets, and will leave a little aside the remaining, very vast area of magnetic (better said, electromagnetic, in memory of Maxwell) phenomena. Our units of measurement will be those accepted in SI (kilogram, meter, second, ampere) and their derivatives:
l Field strength , H, A/m (amps per meter).
This quantity characterizes the field strength between parallel conductors, the distance between which is 1 m, and the current flowing through them is 1 A. The field strength is a vector quantity.
l Magnetic induction , B, Tesla, magnetic flux density (Weber/m2)
This is the ratio of the current through the conductor to the length of the circle, at the radius at which we are interested in the magnitude of induction. The circle lies in the plane that the wire intersects perpendicularly. This also includes a factor called magnetic permeability.
This is a vector quantity. If you mentally look at the end of the wire and assume that the current flows in the direction away from us, then the magnetic force circles “rotate” clockwise, and the induction vector is applied to the tangent and coincides with them in direction.
l Magnetic permeability , μ (relative value)
If we take the magnetic permeability of vacuum as 1, then for other materials we will obtain the corresponding values. So, for example, for air we get a value that is almost the same as for vacuum. For iron we get significantly larger values, so we can figuratively (and very accurately) say that iron “pulls” magnetic lines of force into itself. If the field strength in a coil without a core is equal to H, then with a core we get μH.
l Coercive force , A/m.
Coercive force measures how much a magnetic material resists demagnetization and remagnetization. If the current in the coil is completely removed, then there will be residual induction in the core. To make it equal to zero, you need to create a field of some intensity, but in reverse, that is, let the current flow in the opposite direction. This tension is called coercive force.
Since magnets in practice are always used in some connection with electricity, it should not be surprising that such an electrical quantity as ampere is used to describe their properties.
From what has been said, it follows that it is possible, for example, for a nail that has been acted upon by a magnet to become a magnet itself, albeit a weaker one. In practice, it turns out that even children who play with magnets know about this.
There are different requirements for magnets in technology, depending on where these materials go. Ferromagnetic materials are divided into “soft” and “hard”. The first ones are used to make cores for devices where the magnetic flux is constant or variable.
You cannot make a good independent magnet from soft materials.
They demagnetize too easily, and this is precisely their valuable property, since the relay must “release” if the current is turned off, and the electric motor should not heat up - excess energy is spent on magnetization reversal, which is released in the form of heat.
WHAT DOES A MAGNETIC FIELD REALLY LOOK LIKE? Igor Beletsky
Permanent magnets, that is, those that are called magnets, require hard materials for their manufacture. Rigidity refers to magnetic, that is, a large residual induction and a large coercive force, since, as we have seen, these quantities are closely related to each other. Such magnets are used in carbon, tungsten, chromium and cobalt steels. Their coercivity reaches values of about 6500 A/m.
There are special alloys called alni, alnisi, alnico and many others, as you might guess they include aluminum, nickel, silicon, cobalt in various combinations, which have a greater coercive force - up to 2000060000 A/m. Such a magnet is not so easy to tear off from iron.
There are magnets specifically designed to operate at higher frequencies. This is the well-known “round magnet”. It is “mined” from an unusable speaker from a stereo system, or a car radio, or even a TV of yesteryear. This magnet is made by sintering iron oxides and special additives. This material is called ferrite, but not every ferrite is specifically magnetized this way. And in speakers it is used for reasons of reducing useless losses.
Magnet force field
Magnets. Discovery. How it works?
What happens inside a magnet?
Due to the fact that atoms of a substance are peculiar “clumps” of electricity, they can create their own magnetic field, but only in some metals that have a similar atomic structure is this ability very strongly expressed. Iron, cobalt, and nickel are located next to each other in Mendeleev’s periodic table, and have similar structures of electronic shells, which turns the atoms of these elements into microscopic magnets.
Since metals can be called a frozen mixture of various very small crystals, it is clear that such alloys can have a lot of magnetic properties. Many groups of atoms can “unfold” their own magnets under the influence of neighbors and external fields. Such “communities” are called magnetic domains, and form very bizarre structures that are still being studied with interest by physicists. This is of great practical importance.
As already mentioned, magnets can be almost atomic in size, so the smallest size of a magnetic domain is limited by the size of the crystal in which the magnetic metal atoms are embedded. This explains, for example, the almost fantastic recording density on modern computer hard drives, which, apparently, will continue to grow until the drives have more serious competitors.
Magnetic force field
Gravity, magnetism and electricity
Where are magnets used?
In addition to electric motors, transformers, relays, the cores of which are magnets made of magnets, although they are usually called simply cores, magnets have many other applications. There are stationery magnets, magnets for latching furniture doors, and chess magnets for travelers. These are magnets known to everyone.
Rarer types include magnets for charged particle accelerators; these are very impressive structures that can weigh tens of tons or more. Although now experimental physics is overgrown with grass, with the exception of that part that immediately brings super-profits on the market, but itself costs almost nothing.
Another interesting magnet is installed in a fancy medical device called a magnetic resonance imaging scanner. (Actually, the method is called NMR, nuclear magnetic resonance, but in order not to frighten people who are generally not strong in physics, it was renamed.) The device requires placing the observed object (the patient) in a strong magnetic field, and the corresponding magnet has frightening dimensions and the shape of the devil's coffin.
A person is placed on a couch and rolled through a tunnel in this magnet while sensors scan the area of interest to doctors. In general, it’s not a big deal, but some people experience claustrophobia to the point of panic. Such people will willingly allow themselves to be cut alive, but will not agree to an MRI examination. However, who knows how a person feels in an unusually strong magnetic field with an induction of up to 3 Tesla, after having paid good money for it.
To achieve such a strong field, superconductivity is often used by cooling a magnet coil with liquid hydrogen. This makes it possible to “pump up” the field without fear that heating the wires with a strong current will limit the capabilities of the magnet. This is not a cheap setup at all. But magnets made of special alloys that do not require current biasing are much more expensive.
Our Earth is also a large, although not very strong, magnet. It helps not only the owners of the magnetic compass, but also saves us from death. Without it, we would be killed by solar radiation. The picture of the Earth's magnetic field, simulated by computers based on observations from space, looks very impressive.
Here is a short answer to the question about what a magnet is in physics and technology.
Source: https://www.13min.ru/nauka/chto-takoe-magnit/
Russian wine will appear in advertising
Legislation in FMCG trade, food retail, alcohol January 20, 2020, 18:16 648 views
The FAS allowed advertising of Russian wine without specifying specific brands, thus effectively removing it from the scope of the Law “On Advertising,” which prohibits almost any advertising of alcohol, Kommersant writes.
The Ministry of Industry and Trade was able to obtain permission from the Federal Antimonopoly Service (FAS) to advertise the Russian wine industry as such. Legislative restrictions will not apply to the “Russian Wine Days” campaign, provided that its advertising does not contain the names of specific companies and brands.
Russian Wine Days have been held by the Ministry of Industry and Trade jointly with the Ministry of Agriculture and ANO Roskachestvo since 2018 twice a year. The main purpose of the event is to inform visitors and popularize Russian-made wines among the population. In 2020, the event will take place from April 20 to May 31 and from October 12 to November 22.
Retail chains and stores of various formats will participate in the promotion.
Earlier it was reported that Putin signed the law “On viticulture and winemaking.”
In addition, the Federation Council approved the law “On viticulture and winemaking.”
Retail.ru
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The FAS allowed advertising of Russian wine without specifying specific brands, thus effectively removing it from the scope of the Law “On Advertising,” which prohibits almost any advertising of alcohol, Kommersant writes.
The Ministry of Industry and Trade was able to obtain permission from the Federal Antimonopoly Service (FAS) to advertise the Russian wine industry as such. Legislative restrictions will not apply to the “Russian Wine Days” campaign, provided that its advertising does not contain the names of specific companies and brands.
Russian Wine Days have been held by the Ministry of Industry and Trade jointly with the Ministry of Agriculture and ANO Roskachestvo since 2018 twice a year. The main purpose of the event is to inform visitors and popularize Russian-made wines among the population. In 2020, the event will take place from April 20 to May 31 and from October 12 to November 22.
Retail chains and stores of various formats will participate in the promotion.
Magnetic field theory and interesting facts about the Earth's magnetic field
Let's understand together what a magnetic field is. After all, many people live in this field all their lives and don’t even think about it. It's time to fix it!
A magnetic field
A magnetic field is a special type of matter. It manifests itself in the action on moving electric charges and bodies that have their own magnetic moment (permanent magnets).
Important: the magnetic field does not affect stationary charges! A magnetic field is also created by moving electric charges, or by a time-varying electric field, or by the magnetic moments of electrons in atoms. That is, any wire through which current flows also becomes a magnet!
Magnet
A magnet is a body that has its own magnetic field.
A magnet has poles called north and south. The designations “north” and “south” are given for convenience only (like “plus” and “minus” in electricity).
The magnetic field is represented by magnetic lines of force . The lines of force are continuous and closed, and their direction always coincides with the direction of action of the field forces. If metal shavings are scattered around a permanent magnet, the metal particles will show a clear picture of the magnetic field lines coming out of the north pole and entering the south pole. Graphic characteristic of a magnetic field - lines of force.
Magnetic field pattern
Characteristics of the magnetic field
The main characteristics of a magnetic field are magnetic induction , magnetic flux and magnetic permeability . But let's talk about everything in order.
Let us immediately note that all units of measurement are given in the SI .
Magnetic induction B is a vector physical quantity, which is the main force characteristic of the magnetic field. Denoted by the letter B. The unit of measurement of magnetic induction is Tesla (T ).
Magnetic induction shows how strong the field is by determining the force it exerts on a charge. This force is called the Lorentz force .
Here q is the charge, v is its speed in the magnetic field, B is the induction, F is the Lorentz force with which the field acts on the charge.
Magnetic flux Ф is a physical quantity equal to the product of magnetic induction by the area of the circuit and the cosine between the induction vector and the normal to the plane of the circuit through which the flux passes. Magnetic flux is a scalar characteristic of a magnetic field.
We can say that magnetic flux characterizes the number of magnetic induction lines penetrating a unit area. Magnetic flux is measured in Webers (Wb) .
Magnetic flux
Magnetic permeability is a coefficient that determines the magnetic properties of a medium. One of the parameters on which the magnetic induction of a field depends is magnetic permeability.
Earth's magnetic field
Our planet has been a huge magnet for several billion years. The induction of the Earth's magnetic field varies depending on the coordinates. At the equator it is approximately 3.1 times 10 to the minus fifth power of Tesla. In addition, there are magnetic anomalies where the value and direction of the field differ significantly from neighboring areas. Some of the largest magnetic anomalies on the planet are the Kursk and Brazilian magnetic anomalies .
The origin of the Earth's magnetic field still remains a mystery to scientists. It is assumed that the source of the field is the liquid metal core of the Earth. The core is moving, which means the molten iron-nickel alloy is moving, and the movement of charged particles is the electric current that generates the magnetic field. The problem is that this theory ( geodynamo ) does not explain how the field is kept stable.
Earth's magnetic field
The Earth is a huge magnetic dipole. The magnetic poles do not coincide with the geographic ones, although they are in close proximity. Moreover, the Earth's magnetic poles move. Their displacement has been recorded since 1885.
For example, over the past hundred years, the magnetic pole in the Southern Hemisphere has shifted almost 900 kilometers and is now located in the Southern Ocean. The pole of the Arctic hemisphere is moving through the Arctic Ocean to the East Siberian magnetic anomaly; its movement speed (according to 2004 data) was about 60 kilometers per year.
Now there is an acceleration of the movement of the poles - on average, the speed is growing by 3 kilometers per year.
What is the significance of the Earth's magnetic field for us? First of all, the Earth's magnetic field protects the planet from cosmic rays and solar wind. Charged particles from deep space do not fall directly to the ground, but are deflected by a giant magnet and move along its lines of force. Thus, all living things are protected from harmful radiation.
Earth's magnetic field
Over the history of the Earth, several reversals (changes) of magnetic poles have occurred. A pole reversal is when the poles change places. The last time this phenomenon occurred was about 800 thousand years ago, and in total there were more than 400 geomagnetic inversions in the history of the Earth. Some scientists believe that, given the observed acceleration of the movement of the magnetic poles, the next pole inversion should be expected in the next couple of thousand years.
Fortunately, a pole change is not yet expected in our century. This means that you can think about pleasant things and enjoy life in the good old constant field of the Earth, having considered the basic properties and characteristics of the magnetic field. And so that you can do this, there are our authors, to whom you can confidently entrust some of the educational troubles with confidence! Coursework on international and national law and other types of work you can order using the link.
Source: https://Zaochnik-com.ru/blog/teoriya-magnitnogo-polya-i-interesnye-fakty-o-magnitnom-pole-zemli/
