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What does magnet mean? Encyclopedia of Magnetism – What is magnetism

Where magnetite deposits were discovered in ancient times.

The simplest and smallest magnet can be considered an electron. The magnetic properties of all other magnets are due to the magnetic moments of the electrons inside them. From the point of view of quantum field theory, electromagnetic interaction is carried by a massless boson - a photon (a particle that can be represented as a quantum excitation of the electromagnetic field).

Weber- magnetic flux, when it decreases to zero, an amount of electricity of 1 coulomb passes through a circuit connected to it with a resistance of 1 ohm.

Henry- international unit of inductance and mutual induction. If a conductor has an inductance of 1 H and the current in it varies uniformly by 1 A per second, then an emf of 1 volt is induced at its ends. 1 henry = 1.00052 10 9 absolute electromagnetic units of inductance.

Tesla- a unit of measurement of magnetic field induction in SI, numerically equal to the induction of such a uniform magnetic field in which a force of 1 newton acts on 1 meter of length of a straight conductor perpendicular to the magnetic induction vector with a current of 1 ampere.

Use of magnets

Magnetic storage media: VHS cassettes contain reels of magnetic tape. Video and audio information is encoded onto a magnetic coating on the tape. Also, in computer floppy disks and hard drives, data is recorded on a thin magnetic coating. However, storage media are not magnets in the strict sense, since they do not attract objects. Magnets in hard drives are used in drive and positioning motors.
Credit, debit, and ATM cards all have a magnetic stripe on one side. This band encodes the information needed to connect to a financial institution and link to their accounts.
Conventional TVs and Computer Monitors: TVs and computer monitors containing a cathode ray tube use an electromagnet to control a beam of electrons and form an image on the screen. Plasma panels and LCD displays use different technologies.
Loudspeakers and Microphones: Most loudspeakers use a permanent magnet and a current coil to convert electrical energy (the signal) into mechanical energy (the movement that creates sound). The winding is wound on a coil, attached to the diffuser, and an alternating current flows through it, which interacts with the field of a permanent magnet.
Another example of the use of magnets in audio engineering is in the pickup head of an electrophone and in cassette recorders as an economical erasing head.

Magnetic heavy mineral separator

Electric motors and generators: Some electric motors (as well as loudspeakers) rely on a combination of an electromagnet and a permanent magnet. They convert electrical energy into mechanical energy. A generator, on the other hand, converts mechanical energy into electrical energy by moving a conductor through a magnetic field.
Transformers: Devices that transfer electrical energy between two windings of wire that are electrically insulated but coupled magnetically.
Magnets are used in polarized relays. Such devices remember their state when the power is turned off.
Compasses: A compass (or marine compass) is a magnetized pointer that can rotate freely and aligns itself with the direction of a magnetic field, most commonly the Earth's magnetic field.
Art: Vinyl magnetic sheets can be attached to paintings, photographs and other decorative items, allowing them to be attached to refrigerators and other metal surfaces.

Magnets are often used in toys. M-TIC uses magnetic bars connected to metal spheres

Egg-shaped rare earth magnets that attract each other

Toys: Given their ability to resist gravity at close range, magnets are often used in children's toys with fun effects.
Magnets can be used to make jewelry. Necklaces and bracelets can have a magnetic clasp, or can be made entirely from a series of linked magnets and black beads.
Magnets can pick up magnetic objects (iron nails, staples, tacks, paper clips) that are either too small, difficult to reach, or too thin to handle with your fingers. Some screwdrivers are specially magnetized for this purpose.
Magnets can be used in scrap metal processing to separate magnetic metals (iron, steel and nickel) from non-magnetic ones (aluminum, non-ferrous alloys, etc.). The same idea can be used in what is called a "Magnetic Test", in which the car body is examined with a magnet to identify areas repaired using fiberglass or plastic putty.
Maglev: Magnetic levitation train driven and controlled by magnetic forces. Such a train, unlike traditional trains, does not touch the rail surface during movement. Since there is a gap between the train and the moving surface, friction is eliminated, and the only braking force is the force of aerodynamic drag.
Magnets are used in furniture door latches.
If magnets are placed in sponges, then these sponges can be used to wash thin sheets of non-magnetic materials on both sides at once, with one side being difficult to reach. This could be, for example, the glass of an aquarium or balcony.
Magnets are used to transmit torque “through” a wall, which could be, for example, a sealed container of an electric motor. This is how the GDR toy “Submarine” was designed. In the same way, in household water flow meters, rotation is transmitted from the sensor blades to the counting unit.
Magnets together with a reed switch are used in special position sensors. For example, in refrigerator door sensors and security alarms.
Magnets together with a Hall sensor are used to determine the angular position or angular velocity of the shaft.
Magnets are used in spark gaps to speed up arc extinction.
Magnets are used for non-destructive testing using the magnetic particle method (MPC)
Magnets are used to deflect beams of radioactive and ionizing radiation, such as in surveillance cameras.
Magnets are used in indicating instruments with a deflecting needle, such as an ammeter. Such devices are very sensitive and linear.
Magnets are used in microwave valves and circulators.
Magnets are used as part of a deflection system of cathode ray tubes to adjust the trajectory of the electron beam.
Before the discovery of the law of conservation of energy, there were many attempts to use magnets to build a “perpetual motion machine”. People were attracted by the seemingly inexhaustible energy of the magnetic field of permanent magnets, which have been known for a very long time. But the working model was never built.
Magnets are used in non-contact brake designs consisting of two plates, one is a magnet and the other is made of aluminum. One of them is rigidly fixed to the frame, the other rotates with the shaft. Braking is controlled by the gap between them.

Magnetic toys

Uberorbs
Magnetic constructor
Magnetic drawing board
Magnetic letters and numbers
Magnetic checkers and chess

Medicine and safety issues

Due to the fact that human tissue has a very low level of susceptibility to static magnetic fields, there is no scientific evidence of its effectiveness for use in the treatment of any disease. For the same reason, there is no scientific evidence of a risk to human health associated with exposure to this field. However, if a ferromagnetic foreign body is in human tissue, the magnetic field will interact with it, which can pose a serious danger.

Magnetization

Demagnetization

Sometimes the magnetization of materials becomes undesirable and it becomes necessary to demagnetize them. Demagnetization of materials is achieved in various ways:

heating a magnet above the Curie temperature always leads to demagnetization;
place a magnet in an alternating magnetic field that exceeds the coercive force of the material, and then gradually reduce the effect of the magnetic field or remove the magnet from it.

The latter method is used in industry for demagnetizing tools, hard drives, erasing information on magnetic cards, and so on.

Partial demagnetization of materials occurs as a result of impacts, since a sharp mechanical impact leads to disorder of domains.

Notes

Literature

Savelyev I. V. General physics course. - M.: Nauka, 1998. - T. 3. - 336 p. - ISBN 9785020150003

My favorite games are different types of construction sets. For my birthday in 1st grade I was given a magnetic construction set. My younger brother Nikita and I really enjoy playing it. One day we were building castles and using a construction set and various objects for this, and suddenly I saw that Nikita was upset because the coin with which he had decorated the turret was not magnetic and was falling. I wondered why this was happening. I used to think that a magnet attracts anything metallic. Mom suggested that I study this issue in more detail. This is how the topic of our research work appeared.

Target our work: to identify the basic properties of a magnet.

Tasks:

We have put forward the following hypothesis:

If we know the properties of a magnet, the scope of its application will expand.

Object of study: magnet.

Subject of study: properties of a magnet.

Methods: theoretical, experimental.

Practical significance: This work can be used to explain the properties of a magnet; practically made games can be used to develop attention, imagination, thinking, and fine motor skills.

Relevance The chosen topic is that in the process of experimentation we learned some features of the world around us. The information received may be useful to me in the future in design, when studying physics in high school, we use the manufactured games for entertainment.

1. Theoretical part.

1.1. What is a "magnet"?

The word “magnet” has been known to everyone since childhood. We are accustomed to magnets and sometimes we don’t even realize how many magnets there are around us. There are dozens of magnets in our apartments: in speakers, tape recorders, in watches, in plastic cards. We ourselves are also magnets: the biocurrents flowing in us give rise to a bizarre pattern of magnetic lines of force around us. The earth we live on is a giant magnet.

Magnet is a body that has a magnetic field. Magnetic force - the force with which objects are attracted to a magnet. In nature, magnets are found in the form of pieces of stone - magnetic iron ore (magnetite). It can attract other similar stones to itself. In many languages of the world, the word “magnet” simply means “loving” - this is said about its ability to attract to itself.

Magnets can be natural or artificial. Natural magnets are machined from pieces of magnetic iron ore. Artificial magnets can be obtained by rubbing a piece of magnetic iron ore in one direction on iron bars or simply by placing a non-magnetized sample against a permanent magnet. Interestingly, this method can produce artificial magnets that are much stronger than the original ones. Bodies that retain magnetization for a long time are called permanent magnets.

The most interesting facts about magnets:

According to scientists, birds are the only creatures in the world that can see and feel the Earth's magnetic fields. It is this ability that helps them not to lose their way when searching for a home over long flight distances.

The Earth is a giant magnet that holds everything around it and creates a force of gravity. Compass needles are oriented according to the earth's magnetic field.

In November 1954, John Wheatley received a patent for the idea of using a magnet to hold lightweight objects such as notes, notes, paper on refrigerators and other metal surfaces.

The idea of using a refrigerator magnet was first invented by William Zimmerman in the early 1970s. William Zimmerman received a patent for small cartoon colored magnets that can be used both for convenience and as decoration elements.

the now famous hobby of “collecting magnets” is partly the creation of everyday pragmatists. Magnets initially gained popularity for being used to hide scratches and defects on household appliances, as well as for attaching various notes and reminders.

According to ROMIR Monitoring surveys conducted in 2007, 86% of respondents decorate their refrigerator in one way or another. Of these, 78% have some collection of magnets.

The world record for the most refrigerator magnets belongs to Louise Greenfarb, who lives in Henderson, Nevada, USA. Today, Louise has more than 40,000 magnets in her collection. Louise calls herself a "magnetic lady."

there is a Guinness Museum in Hollywood that displays over 7,000 magnets (part of the Louise Greenfarb collection).

There is one old legend about a magnet, it talks about a shepherd named Magnus. He once discovered that the iron tip of his stick and the nails of his boots were attracted to the black stone. This stone began to be called the “Magnus stone” or simply “magnet”, after the name of the area where iron ore was mined (the hills of Magnesia in Asia Minor). Thus, many centuries BC it was known that some rocks have the property of attracting pieces of iron.

In fact, more than two thousand years ago, the ancient Greeks learned about the existence of magnetite, a mineral that is able to attract iron. Magnetite owes its name to the ancient Turkish city of Magnesia, where the ancient Greeks found this mineral. Now this city is called Maniza, and magnetic stones are still found there. Pieces of found stones are called magnets or natural magnets. Over time, people learned to make magnets themselves by magnetizing pieces of iron.

In Russia, magnetic ore was found in the Urals. More than 300 years ago, local hunters were surprised that the horseshoes were attracted to the ground and considered this place cursed. And in 1720, the extraction of iron ore from Mount Magnit began.

Magnet is a body capable of attracting iron, steel, nickel and some other metals.

The word "magnet" comes from the name of the province of Magnesia (in Greece), whose inhabitants were called magnets. This is what Titus Lucretius Carus argued in his poem “On the Nature of Things.” Before our era, Pythagoras, Hippocrates, Plato, Epicurus, Aristotle, and Lucretius wrote about magnets in one way or another.

In 1269, Pierre Peregrine from Maricourt wrote the book “Letters on the Magnet,” in which he collected a lot of information about the magnet that had accumulated before him and was discovered by him personally. Peregrine speaks for the first time about the poles of magnets, about the attraction of unlike poles and the repulsion of like ones, about the production of artificial magnets by rubbing iron with a natural magnet, about the penetration of magnetic forces through glass and water, about the compass.

In 1600, the book “On the Magnet, Magnetic Bodies and the Great Magnet - the Earth” was published. New physiology, proven by many arguments and experiments” by the English physician William Gilbert from Colchester. Gilbert discovered that when a magnet is heated above a certain temperature, its magnetic properties disappear, and that when a piece of iron is brought closer to one pole of the magnet, the other pole begins to attract more strongly. Gilbert also discovered that objects made of soft iron, lying motionless for a long time, acquire magnetization in the north-south direction. The magnetization process is accelerated if the iron is tapped with a hammer.

1.3. Scope of application of magnets.

Magnets surround us all the time. We noticed that magnetic force is used both at home and at school: with the help of magnets we attach notes to the refrigerator at home, and at school we attach posters to the board; There are magnetic fastenings on cabinet doors, bags, doors, and phone cases.

Representatives of various sciences take magnetic fields into account in their research: a physicist measures the magnetic fields of atoms and elementary particles, an astronomer studies the role of cosmic fields in the process of the formation of new stars, a geologist uses anomalies in the Earth’s magnetic field to find deposits of magnetic ores.

Magnets are widely used in the healthcare sector. As a local external remedy and as an amulet, the magnet enjoyed great success among the Chinese, Hindus, Egyptians, Arabs, Greeks, Romans, etc. The philosopher Aristotle and the historian Pliny mention its medicinal properties in their works. In the second half of the 20th century, magnetic bracelets became widespread, having a beneficial effect on patients with blood pressure disorders (hypertension and hypotension).

There are electromagnetic blood velocity meters, miniature capsules that, using external magnetic fields, can be moved through blood vessels to expand them, take samples at certain parts of the path, or, conversely, locally remove various medications from the capsules. A magnetic method for removing metal particles from the eye is widely used.

Magnets are also widely used in magnetic therapy, including magnetic belts, massagers, mattresses, etc. Medical institutions use magnetic resonance techniques to scan various organs in the body.

In addition to permanent magnets, electromagnets are also used. They are also used for a wide range of problems in science, technology, electronics, medicine (nervous diseases, vascular diseases of the extremities, cardiovascular diseases, etc.).

Nowadays, due to their ability to attract objects underwater, magnets are used in the construction and repair of underwater structures. Due to the property of magnets to act at a distance and through solutions, they are used in chemical and medical laboratories, where it is necessary to mix sterile substances in small quantities.

Previously, only natural magnets were used - pieces of magnetite; now most magnets are artificial. And the strongest of them are electromagnets, which are used in enterprises. They are used in industrial equipment such as separators, iron separators, conveyors and welding devices.

Credit, debit, and bank cards have magnetic stripes; on the one hand, they provide access to information about a person, to his account, to opening a magnetic lock, etc.

Some models of cylinder locks use magnetic elements. The lock and key are equipped with matching code sets of permanent magnets. When the correct key is inserted into the keyhole, it attracts and positions the internal magnetic elements of the lock, allowing the lock to open.

Magnets are used in speakers, hard drives, as well as in speaker systems, loudspeakers and microphones. Motors and generators also operate using magnets. Household appliances, telephones, television, refrigerators, water pumps, etc. - also use magnets.

Magnets are used in jewelry such as bracelets, earrings, pendants and necklaces.

Other examples of the use of magnets are tools, toys, compasses, car speedometers, etc. A magnet is needed to conduct current through wires. Magnetic levitation trains reach high speeds.

Magnets are also used in veterinary practice to treat animals that often swallow metal objects along with food. These objects can damage the animal's stomach walls, lungs, or heart. Therefore, before feeding, farmers use a magnet to clean the food.

Even more curious is the useful service that a magnet provides in agriculture, helping the farmer to clear the seeds of cultivated plants from weed seeds. Weeds have fuzzy seeds that cling to the fur of passing animals and thus spread far from the mother plant. This feature of weeds, developed over millions of years of struggle for existence, was used by agricultural machinery to separate the rough weed seeds from the smooth seeds of useful plants such as flax, clover, and alfalfa using a magnet.

If weedy seeds of cultivated plants are sprinkled with iron powder, then the grains of iron will tightly adhere to the weed seeds, but will not stick to the smooth seeds of useful plants. Then falling into the field of action of a sufficiently strong electromagnet, the mixture of seeds is automatically separated into clean seeds and into impurities: the magnet catches from the mixture all those seeds that are covered with iron filings.

The simplest conclusion that can be drawn from the above is that there is no area of applied human activity where magnets are used.

2. Practical part.

2.1. Experiment “Does a magnetic field exist?”

Equipment: 2 horseshoe magnets, metal filings, cardboard.

Procedure of the experiment: We poured metal filings onto a sheet of cardboard and distributed them in a thin, even layer, then placed 2 magnets from below, under the sheet of cardboard. The sawdust began to change its location depending on where the magnets were.

Conclusion: The magnetic field is not visible, but it exists.

2.2. Experiment “How do magnets interact?”

Equipment: 2 flat magnets, 2 trailers with magnets.

Progress of the experiment: We brought magnets to each other with like and opposite ends. Similarly, trailers with magnets were moved towards each other.

Conclusion: Magnets of the same name repel, and magnets of the same name attract.

2.3. Experiment “What is the effect of a magnetic field on a compass needle?”

Equipment: compass, flat magnet.

Progress of the experiment: We observed the compass needle. In a static state, it shows the same direction: north - south. Then we brought a magnet to the compass. The compass needle is attracted by the magnet and points towards it.

Conclusion: The magnetic field affects the compass needle. The compass needle changes its direction and points to the magnet.

2.4. Experiment “Are all bodies attracted by magnets?”

Equipment: 2 magnets, non-metallic objects: sponge, plastic, paper, cardboard, wood, rubber, fabric; metal objects: gold, silver, iron; coins of different denominations: 5 kopecks, 10 kopecks, 50 kopecks, 1 ruble, 2 rubles, 5 rubles, 10 rubles.

Procedure of the experiment: We brought a magnet to each material one by one and checked whether the magnet attracted it.

Conclusion: A magnet does not attract non-metallic objects, and not all metallic ones attract: a magnet attracts objects made of iron, but does not attract silver and gold. The magnet attracted coins of 5 kopecks, 10 kopecks, 2 rubles, 10 rubles, but did not attract coins of 50 kopecks, 1 ruble, 5 rubles (See Appendix 1).

2.5. Experiment “Does the force of attraction depend on the surface area of a magnet?”

Equipment: 2 magnets of different sizes, metal filings, paper clips, nuts, bolts.

Procedure of the experiment: First, we took metal filings and brought 2 magnets to them: one with a diameter of 12 mm, the other with a diameter of 18 mm. We saw how many metal filings were attracted by the large magnet, and how many by the small one. Then we brought these 2 magnets one by one to metal clips, nuts and bolts. We counted how many objects each magnet attracted (See Appendix 2).

Conclusion: A magnet with a larger diameter attracts more metal objects.

2.6. Experiment “Does the force of attraction depend on the distance between bodies?”

Equipment: magnets of different sizes, ruler, metal clip.

Procedure of the experiment: We placed a metal paperclip on the ruler next to the “0” mark and took magnets of different sizes, gradually bringing them to the paperclip to see if they would begin to attract it from the same distance. The small magnet attracted the paper clip from a distance of 2mm, and the large one from a distance of 7mm.

Conclusion: Magnets attract even from a distance. The larger the magnet, the greater the force of attraction and the greater the distance over which the magnet exerts its influence.

2.7. Experiment “Can magnetic force pass through objects?”

Equipment: magnet, metal clips, paper, cardboard, fabric, glass, plastic, wood, glass cup, water, metal clips.

Procedure of the experiment: We placed metal clips alternately on paper, cardboard, fabric, glass, plastic, wood, and moved a magnet under the material to check whether the magnetic force acts through different materials. Then we poured water into a glass. We dipped a paperclip into the water and tried to get it out using a magnet. We did it.

Conclusion: Magnetic force can pass through various objects, in particular through paper, cardboard, fabric, plastic, wood, glass, in particular a glass glass of water.

2.8. Making magnetic games.

The second part of my practical work on the research topic is making my own games using magnets. There are already many such games. For example, we have games such as “Darts”, “Fishing”, “Labyrinth”, “Railway”, “Constructor”.

I came up with several ideas for making games. In my work I implemented 3 ideas.

Game "Flower Meadow".

Using cardboard, colored paper, colored pictures, glue and magnets, I made the game “Flower Meadow”. With this game you can show small children how a butterfly flies from flower to flower, or how a ladybug crawls across a clearing. This game develops children's imagination and fine motor skills.

Game "Turnip".

Using cardboard, colored paper, colored images of characters, glue and magnets, I made the game “Turnip”. This game is about dramatizing the fairy tale “Turnip”. With the help of magnets attached to the characters, it became possible to move the characters and show this fairy tale in motion. The game develops children's spatial imagination, attention, and fine motor skills.

Game "Racing".

Using cardboard, paints, brushes, felt-tip pens, glue, two cars and magnets, I made a “Racing” game. This game must have 2 participants. Each participant is given a racing car with a magnet and a magnet. Both cars are placed at the start and on command, without touching the cars with their hands, but only with the help of magnets moving under the race track, the participants drive their cars to the finish line. This game develops imagination, attention, thinking and fine motor skills.

Conclusion.

Purpose his I put the work: identify the basic properties of a magnet.

Tasks, by solving which I achieved my goal :

study literature on this topic;

experimentally identify the properties of a magnet;

make your own games using magnets.

I have achieved all my goals and objectives.

I put forward the next one hypothesis:

If we know the properties of a magnet, its scope will expand.

Our hypothesis was confirmed.

Having completed our work, we made the following conclusions:

the magnetic field exists and can be represented using metal filings;

a magnet has 2 poles: north and south, and they interact with each other;

the magnet acts on the compass needle;

a magnet does not attract non-metallic objects, and not all metallic objects are attracted;

a magnet with a larger diameter attracts more metal objects;

a magnet with a larger diameter has a greater attractive force and exerts its influence over a greater distance;

The magnetic force can pass through objects and liquids, but it is weakened when doing so.

By observing various objects at home and at school, I found out that magnets are still widely used today. People are accustomed to using the power of a magnet; many devices and toys operate with its help.

Working on the research turned out to be very interesting and exciting. I think that by carrying out a research project, I acquired the ability to critically work with the information received, analyze and compare existing facts, and find ways to solve emerging problems. I will need all this for my further successful continuation of education.

The ability of a magnet to attract certain objects has not lost its enchanting mystery to this day. A person has not yet been born and probably never will be born who could say: “I know EVERYTHING about magnets.” Why does a magnet attract? - this question will always inspire an inexplicable excitement in front of the beautiful mystery of nature, and give rise to a thirst for new knowledge and new discoveries. I have a question: can a magnet lose its power or does it have it forever? To answer this question, I will continue to study magnets.

List of sources and literature used

Big book of experiments for schoolchildren / Ed. Antonella Meijani; Per. with it. E.I. Motyleva. - M.: ZAO ROSMEN-PRESS, 2006. - 260 p.

Entertaining experiments: Electricity and magnetism. / M. Di Spezio; Per. from English M. Zabolotskikh, A. Rastorgueva. - M.: AST: Astrel, 2005, - 160 pp.: ill.

Mneyan M.G. New magnet professions: Book. For extracurricular activities. readings M.: Education, 1985. - 144 p., ill. - (World of Knowledge)

Pasynkov V.V., Sorokin V.S. Practical use of magnets, M.: Higher School, 1986 - 252 p.

Perelman Ya.I.. Entertaining physics. In 2 books. Book 2 / Ed. A.V. Mitrofanova. - M.: Nauka, 2001. - 272 p., ill.

What? For what? Why? Big book of questions and answers / Transl. K. Mishina, A. Zykova. - M.: Eksmo, 2007. - 512 p.: ill.

I explore the world: Children's encyclopedia: Physics / Comp. A.A. Leonovich; Under general ed. O.G. Hinn. - M.: LLC Publishing House AST-LTD, 2003. - 480 p.

Annex 1.

Table 1 “Do magnets attract everything?”

	Material	Does a magnet attract

	plastic








	5 kopeck coin
	10 kopeck coin
	50 kopeck coin
	1 ruble coin
	2 ruble coin
	5 ruble coin
	10 ruble coin

Appendix 2.

Table 2 “Does the force of attraction depend on the surface area of a magnet?”

There are two main types of magnets: permanent and electromagnets. You can determine what a permanent magnet is based on its main properties. A permanent magnet gets its name because its magnetism is always “on.” It generates its own magnetic field, unlike an electromagnet, which is made of wire wrapped around an iron core and requires current to flow to create a magnetic field.

History of the study of magnetic properties

Centuries ago, people discovered that some types of rocks have an original property: they are attracted to iron objects. Mention of magnetite is found in ancient historical chronicles: more than two thousand years ago in European and much earlier in East Asian. At first it was regarded as a curious object.

Later, magnetite was used for navigation, finding that it tends to occupy a certain position when given the freedom to rotate. Scientific research carried out by P. Peregrine in the 13th century showed that steel could acquire these characteristics after being rubbed with magnetite.

Magnetized objects had two poles: “north” and “south,” relative to the Earth’s magnetic field. As Peregrine discovered, isolating one of the poles was not possible by cutting a fragment of magnetite in two - each individual fragment ended up with its own pair of poles.

In accordance with today's concepts, the magnetic field of permanent magnets is the resulting orientation of electrons in a single direction. Only some types of materials interact with magnetic fields; a much smaller number of them are capable of maintaining a constant magnetic field.

Properties of permanent magnets

The main properties of permanent magnets and the field they create are:

the existence of two poles;
opposite poles attract, and like poles repel (like positive and negative charges);
magnetic force imperceptibly spreads in space and passes through objects (paper, wood);
An increase in MF intensity is observed near the poles.

Permanent magnets support the MP without external assistance. Depending on their magnetic properties, materials are divided into main types:

ferromagnets – easily magnetized;
paramagnetic materials – are magnetized with great difficulty;
Diamagnets - tend to reflect external magnetic fields by magnetizing in the opposite direction.

Important! Soft magnetic materials such as steel conduct magnetism when attached to a magnet, but this stops when it is removed. Permanent magnets are made from hard magnetic materials.

How does a permanent magnet work?

His work deals with atomic structure. All ferromagnets create a natural, albeit weak, magnetic field, thanks to the electrons surrounding the nuclei of atoms. These groups of atoms are able to orient themselves in the same direction and are called magnetic domains. Each domain has two poles: north and south. When a ferromagnetic material is not magnetized, its regions are oriented in random directions, and their magnetic fields cancel each other out.

To create permanent magnets, ferromagnets are heated at very high temperatures and exposed to strong external magnetic fields. This leads to the fact that individual magnetic domains inside the material begin to orient themselves in the direction of the external magnetic field until all domains are aligned, reaching the point of magnetic saturation. The material is then cooled and the aligned domains are locked into position. Once the external MF is removed, hard magnetic materials will retain most of their domains, creating a permanent magnet.

Characteristics of permanent magnet

Magnetic force is characterized by residual magnetic induction. Designated Br. This is the force that remains after the disappearance of the external MP. Measured in tests (T) or gauss (G);
Coercivity or resistance to demagnetization - Ns. Measured in A/m. Shows what the external MF intensity should be in order to demagnetize the material;
Maximum energy – BHmax. Calculated by multiplying the remanent magnetic force Br and coercivity Hc. Measured in MGSE (megaussersted);
Temperature coefficient of residual magnetic force – Тс of Br. Characterizes the dependence of Br on the temperature value;
Tmax – the highest temperature value, upon reaching which permanent magnets lose their properties with the possibility of reverse recovery;
Tcur is the highest temperature value at which the magnetic material irreversibly loses its properties. This indicator is called the Curie temperature.

Individual magnet characteristics change depending on temperature. At different temperatures, different types of magnetic materials perform differently.

Important! All permanent magnets lose a percentage of their magnetism as the temperature rises, but at different rates depending on their type.

Types of permanent magnets

There are five types of permanent magnets, each of which is manufactured differently using materials with different properties:

alnico;
ferrites;
rare earth SmCo based on cobalt and samarium;
neodymium;
polymer.

Alnico

These are permanent magnets consisting primarily of a combination of aluminum, nickel and cobalt, but may also include copper, iron and titanium. Due to the properties of alnico magnets, they can operate at the highest temperatures while retaining their magnetism, but they demagnetize more easily than ferrite or rare earth SmCo. They were the first mass-produced permanent magnets, replacing magnetized metals and expensive electromagnets.

Application:

electric motors;
heat treatment;
bearings;
aerospace vehicles;
military equipment;
high temperature loading and unloading equipment;
microphones.

Ferrites

To make ferrite magnets, also known as ceramic, strontium carbonate and iron oxide are used in a ratio of 10/90. Both materials are abundant and economically available.

Due to their low production costs, resistance to heat (up to 250°C) and corrosion, ferrite magnets are one of the most popular magnets for everyday use. They have greater internal coercivity than alnico, but less magnetic strength than their neodymium counterparts.

Application:

sound speakers;
security systems;
large plate magnets for removing iron contamination from process lines;
electric motors and generators;
medical instruments;
lifting magnets;
marine search magnets;
devices based on the operation of eddy currents;
switches and relays;
brakes

Rare Earth SmCo Magnets

Cobalt and samarium magnets operate over a wide temperature range, have high temperature coefficients and high corrosion resistance. This type retains magnetic properties even at temperatures below absolute zero, making them popular for use in cryogenic applications.

Application:

turbo technology;
pump couplings;
wet environments;
high temperature devices;
miniature electric racing cars;
radio-electronic devices for operation in critical conditions.

Neodymium magnets

The strongest existing magnets, consisting of an alloy of neodymium, iron and boron. Thanks to their enormous power, even miniature magnets are effective. This provides versatility of use. Each person is constantly near one of the neodymium magnets. They are, for example, in a smartphone. The manufacture of electric motors, medical equipment, and radio electronics rely on ultra-strong neodymium magnets. Due to their ultra-strength, enormous magnetic force and resistance to demagnetization, samples up to 1 mm are possible.

Application:

hard disks;
sound-reproducing devices – microphones, acoustic sensors, headphones, loudspeakers;
prostheses;
magnetically coupled pumps;
door closers;
engines and generators;
locks on jewelry;
MRI scanners;
magnetic therapy;
ABS sensors in cars;
lifting equipment;
magnetic separators;
reed switches, etc.

Flexible magnets contain magnetic particles inside a polymer binder. Used for unique devices where installation of solid analogues is impossible.

Application:

display advertising – quick fixation and quick removal at exhibitions and events;
vehicle signs, educational school panels, company logos;
toys, puzzles and games;
masking surfaces for painting;
calendars and magnetic bookmarks;
window and door seals.

Most permanent magnets are brittle and should not be used as structural components. They are made in standard forms: rings, rods, disks, and individual: trapezoids, arcs, etc. Neodymium magnets, due to their high iron content, are susceptible to corrosion, so they are coated with nickel, stainless steel, Teflon, titanium, rubber and other materials.

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A magnet is an object that has its own magnetic field. Magnets are capable of attracting iron and some other metals with their field. In this article we will tell you in more detail what a magnet is.

Magnus Stone

According to legend, the first magnet was found by a shepherd named Magnus, who one day discovered that a stone was “sticking” to the iron tip of his shepherd’s stick. The magnet got its name from the shepherd.

Ancient Magnesia

However, there is another theory. In ancient times, in Asia Minor there was a region called Magnesia. Large deposits of magnetite (magnetic iron ore), a black mineral with magnetic properties, were discovered in this region. The mineral was named after the area in which it was discovered. This theory, of course, is somewhat more plausible than the story about the shepherd.

Magnet or magnetism

Magnets are materials that have a magnetic field regardless of the conditions in which they are found. Magnetism is the property of some materials to turn into magnets under the influence of a magnetic field. There are different types of magnetism (paramagnetism, ferromagnetism, diamagnetism, superparamagnetism, etc.), however, every material has at least one.

Magnet Applications

The special properties of magnets have led to their use in many areas - magnetic storage media, credit cards, televisions, monitors, plasma panels, microphones, generators, compasses, etc.; the functioning of these and many other things is based on magnetic materials.

In Soviet times, all magnets had almost the same composition. They were made from ferromagnetic alloys, where the percentage of materials varied. But even then, scientific research was underway to invent new magnets. Today, magnetic production offers a variety of materials that can maintain a magnetic field.

What are different types of magnets made of?

The strength and properties of magnets depend on their composition. The following types of alloys have become widespread.

1. Ferrites
These are compounds of iron oxide Fe2O3 with oxides of other metals that have ferromagnetic properties. They have found application in electronics, radio engineering and other industries where the strength of the magnetic field does not play a special role. These are cheap magnets, so they are used in creating a variety of devices. Ferrites are characterized by corrosion resistance and average temperature stability.

Ferrite magnets are rust and high temperature resistant

2. Alnico alloys
They are a compound of iron with an alloy of aluminum, nickel, copper and cobalt (AlNiCo). Alnico magnets based on this alloy are characterized by high magnetic force and temperature stability, therefore they are used in heating conditions up to 550 degrees Celsius. However, they are not widely used due to their high cost. Such alloys are indispensable in the creation of other permanent magnets.

In school experiments, magnetic bars and horseshoes made of Alnico alloy are usually used.

3. Neodyms
It is an alloy of rare earth metals - neodymium, boron and iron (NdFeB). They have no competitors in terms of power and durability, as they can hold objects that are a thousand times their mass. Neodymium magnets are the result of a complex manufacturing process that involves vacuum melting, pressing, sintering and other manipulations. The only drawback is poor resistance to heat - when heated, they quickly lose their properties. If we exclude thermal shock, then such magnetic elements last almost forever - they lose no more than 1% of power in 100 years.

The bicycle is "fished" with a search magnet. Search magnets are made of neodymium; it has maximum load capacity with minimal dimensions

4. Samarium-cobalt
An alloy of two rare earth metals - cobalt and samarium SmCo5 or Sm2Co17. They are also alloyed with other metals - copper, zirconium, gadolinium, etc. In terms of power, such alloys are inferior to neodymium, but superior to all other analogues. They are resistant to corrosion and temperature effects. Indispensable when working in difficult conditions when reliability and trouble-free operation are required. They are in the same price category as neodymium alloys.

SmCo5 magnets are weaker than neodymium ones, but more powerful than others

5. Polymer permanent magnets
They are made from composite materials with the inclusion of magnetic (usually ferrite-barium) powder. The basis is taken from various polymer components. Magnetic plastics have a low magnetic force, but they are distinguished by unsurpassed corrosion resistance to the extent that other polymers have it. The final properties of each polymer magnet depend on the percentage of the magnetic mixture. If rare-earth magnet powder is used (neodymium-iron-boron, samarium-cobalt), then the magnetoplast becomes more powerful. The main advantage is incredible plasticity, which allows the production of magnets of any shape and size.

The magnetic parameters of magnetoplasts are lower than those of sintered magnets

6. Magnetic vinyl
It is a mixture of rubber and magnetic powder (ferrite). The percentage of the latter is 70-75% by weight. The more of this powder, the higher the magnetic strength of the product. The advantages of the material include wear resistance and a huge range of operating temperatures (from −300°C to +800°C). Magnetic vinyl is moisture resistant and flexible. Due to its flexibility, it is suitable for the manufacture of products of any configuration.