Permanent magnets. Permanent magnet What a magnet is made of

It is difficult to find a person who does not know what a magnet is. More precisely, that a certain metal-like piece can attract various iron objects to itself, as well as mutually attract or mutually repel from another of the same magnet. But not everyone knows the very nature of such phenomena. Although the essence of the magnet is not fraught with special secrets and difficulties. Everything about it is simple enough. Let's consider in this article the cause and nature, which is the basis of the work of the magnet.

So, first of all, let's start with the following. I think you have heard that the basis of the operation of any electrical devices is the movement of electric current through the internal circuits of the device. Electricity is small electrical particles that have a certain electric charge and are orderedly moved inside conductors (everything that conducts current through itself) when such an opportunity arises (when a closed circuit occurs). Particles with a negative charge are commonly referred to as electrons. It is they who do their work (movement) in solids. Ions with a positive charge move in liquid and gaseous substances.

What is the connection between electrically charged particles and magnets that expresses its essence? And the connection is direct! Scientists have long established that a magnetic field arises around a moving electric charge. Also, you may have heard that magnetic fields exist around ordinary wires that carry current. As soon as the current stops moving, then the electromagnetic field also disappears. This is the essence and condition of occurrence magnetic field.

From school physics it is known that any things and objects around us consist of atoms and molecules (small enough elementary particles). These very elementary particles, in turn, have the following structure. Inside there is a nucleus (consisting of protons and neutrons) (the nucleus has a positive charge), and around this nucleus, smaller particles rotate at a tremendous speed, these are electrons (having a negative charge).

So, the essence of a magnet is as follows. Since we found out that a magnetic field arises around moving electric charges, and electrons are in all atoms and molecules, and they are constantly moving, therefore atoms and molecules have magnetic fields around them (they are very small both in strength and size). In addition, it is worth considering that various substances and objects have different magnetic properties. Some have very strong magnetic properties, while others are so weak, which indicates a complete absence of fields.

This is the basis of the nature and essence of a magnet. But even those substances that have a high intensity of the manifestation of magnetic fields (these are ferromagnets, the most famous of which is simple iron) do not always magnet. Why is it so? Because there is an effect of one-pointedness and chaos. Let me explain what it is. The essence of a magnet (manifestation of magnetism) depends not only on the substance, but also on the position of atoms and molecules that is inside the substance. If two magnets are connected in such a way that their poles coincide in direction, then the magnetic force of the fields will strengthen each other and the resulting total field will become stronger. But if these magnets are positioned relative to each other with opposite poles, naturally, they will oppress each other, and their common field will grin. Likewise, inside substances, in order to obtain the greatest magnetic field, it is necessary that all the atoms and molecules of the magnetic substance be unidirectional with their poles. This is accomplished in a variety of ways.

And so, we figured out the very essence of the magnet and its nature of action. Now a little about how magnets are made. If you need to make a permanent magnet (an ordinary piece of magnet that is permanently magnetising), they take material from a ferromagnet, place it in a magnetic field of sufficiently high intensity for a certain time. After which this ferromagnet itself begins to possess magnetic properties. As a result of placing it in a magnetic field of high intensity, the elementary particles of the substance turned in one direction, which caused the appearance of the effect of the unidirectionality of atoms and molecules.

To obtain electromagnets, I use simple copper coils, inside which a ferromagnetic core is placed, which enhances the general magnetic effect. That is, when a direct current is passed through this coil, it begins to attract iron objects to itself. After all, a current (charged particles) flows through the coil. Consequently, an electromagnetic field will also arise around it. And the more turns on the coil and the more current will pass through it, the more magnetic force will be generated around it.

P.S. Here, in principle, we figured out the nature and essence of the magnet. Knowing general principle the device and operation of a magnet (electromagnet) It has now become clear to you why magnets attract iron objects to themselves.

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 explain in more detail what a magnet is.

Magnus Stone

According to legend, the first magnet was found by a shepherd named Magnus, who once discovered that a stone was "sticking" to the iron tip of his shepherd's stick. The magnet got its name from the name of 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, have been discovered in this region. The mineral received the name of the area in which it was discovered. This theory is, of course, somewhat more plausible than the story of the shepherd.

Magnet or magnetism

Magnets are materials that have a magnetic field, regardless of the conditions in which they are located. 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, any of the materials has at least one.

Magnet Applications

The special properties of magnets have determined their use in many areas - magnetic storage media, credit cards, televisions, monitors, plasma panels, microphones, generators, compasses, etc., magnetic materials are the basis for the functioning of these and many other things.

There are two main types of magnets: permanent and electromagnets. It is possible to determine what a permanent magnet is based on its main property. The permanent magnet gets its name from the fact that 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 a 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 original characteristics: they are attracted to iron objects. The mention of magnetite is found in ancient historical annals: more than two millennia ago in European and much earlier in East Asian. At first, it was rated as a curious subject.

Later, magnetite was used for navigation, finding that it tends to take a certain position when it was given freedom of rotation. Scientific research by P. Peregrine in the 13th century showed that steel can acquire these characteristics after rubbing 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 piece of magnetite in two — each individual piece 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, much less of them are able to maintain a constant MF.

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 (as positive and negative charges);
• magnetic force imperceptibly spreads in space and passes through objects (paper, wood);
• there is an increase in the MF intensity near the poles.

Permanent magnets support MP without external aid. Materials, depending on the magnetic properties, are divided into the main types:

• ferromagnets - easily magnetized;
• paramagnets - magnetized with great difficulty;
• diamagnets - tend to reflect the external MF 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 a permanent magnet works

His work is related to atomic structure. All ferromagnets create a natural, albeit weak, MF, thanks to the electrons surrounding the nuclei of atoms. These groups of atoms are capable of orienting in a single 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 MFs cancel each other out.

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

Permanent magnet characteristics

1. The magnetic force is characterized by the residual magnetic induction. It is denoted by Br. This is the force that remains after the disappearance of the external MP. Measured in tests (T) or gauss (G);
2. Coercivity or demagnetization resistance - Нс. Measured in A / m. Shows what the strength of the external MF must be in order to demagnetize the material;
3. Maximum energy - BHmax. It is calculated by multiplying the residual magnetic force Br and the coercivity Hc. Measured in MGSE (megaussersted);
4. The temperature coefficient of the residual magnetic force is Tc of Br. Characterizes the dependence of Br on the temperature value;
5. Tmax - the highest temperature value, upon reaching which permanent magnets lose their properties with the possibility of reverse recovery;
6. Tcur is the highest temperature value when the magnetic material irrevocably loses its properties. This indicator is called the Curie temperature.

The individual characteristics of a magnet vary with temperature. Different types of magnetic materials work differently at different temperatures.

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

Types of permanent magnets

In total, there are five types of permanent magnets, each of which is manufactured in different ways based on materials with different properties:

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

Alniko

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

Application:

• electric motors;
• heat treatment;
• bearings;
• aerospace vehicles;
• military equipment;
• high temperature handling equipment;
• microphones.

Ferrites

For the manufacture of ferrite magnets, also known as ceramic magnets, strontium carbonate and iron oxide are used in a ratio of 10/90. Both materials are abundant and affordable.

Due to their low production costs, resistance to heat (up to 250 ° C) and corrosion, ferrite magnets are among the most popular for everyday use. They have a higher intrinsic coercivity than alnico, but less magnetic force than their neodymium counterparts.

Application:

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

Rare Earth SmCo Magnets

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

Application:

• turbine engineering;
• pump couplings;
• humid environments;
• high temperature devices;
• miniature electric racing cars;
• radio electronic devices for work in critical conditions.

Neodymium magnets

The strongest magnets in existence, composed of an alloy of neodymium, iron and boron. Due to their immense strength, 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, radio electronics rely on heavy-duty neodymium magnets. Due to their super strength, enormous magnetic force and resistance to demagnetization, it is possible to make samples up to 1 mm.

Application:

• hard drives;
• sound reproducing devices - microphones, acoustic sensors, headphones, loudspeakers;
• prostheses;
• magnetically coupled pumps;
• door closers;
• motors and generators;
• locks on jewelry;
• MRI scanners;
• magnetotherapy;
• 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 analogs is impossible.

Application:

• display advertising - quick fixation and quick removal at exhibitions and events;
• signs Vehicle, 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 fragile and should not be used as structural elements... They are manufactured in standard forms: rings, rods, discs, and individual ones: trapeziums, arcs, etc. Neodymium magnets are subject to corrosion due to their high iron content, therefore they are coated on top with nickel, stainless steel, Teflon, titanium, rubber and other materials.

Video

The unique properties of some substances have always amazed people with their uniqueness. Particular attention was drawn to the ability of some metals and stones to repel or be attracted to each other. Throughout all eras, this aroused the interest of the sages and the great surprise of ordinary people.

Starting from the 12th - 13th centuries, it began to be actively used in the production of compasses and other innovative inventions. Today you can see the prevalence and variety of magnets in all areas of our life. Every time we meet another product made of a magnet, we often ask ourselves the question: "So how are magnets made?"

Types of magnets

There are several types of magnets:

• Constant;
• Temporary;
• Electromagnet;

The difference between the first two magnets lies in their degree of magnetization and the time the field is held inside. Depending on the composition, the magnetic field will be weaker or stronger and more resistant to external fields. An electromagnet is not a real magnet, it is just an effect of electricity that creates a magnetic field around the metal core.

Interesting fact: For the first time, research on this substance was carried out by our domestic scientist Peter Peregrin. In 1269 he published "The Book of Magnet", which described the unique properties of matter and its interaction with the outside world.

What are magnets made of?

For the production of permanent and temporary magnets, iron, neodymium, boron, cobalt, samarium, alnico and ferrites are used. They are crushed in several stages and melted, baked or pressed together until a permanent or temporary magnetic field is obtained. Depending on the type of magnets and the required characteristics, the composition and proportions of the components change.

Are you, of course, familiar with the object that is drawn here? It's a magnet. Take such a "horseshoe", bring it to a pin or nail, and they themselves will jump towards you.

It has long been believed that there is some kind of incomprehensible attachment between a magnet and iron objects. In some languages, the magnet is still called the "loving stone". For many centuries, they showed experiments with natural magnets - pieces of magnetic iron ore, but no one could explain the reason for their "love" for everything iron. The only benefit that a magnet could bring then was that a compass was made of it: a movable magnetic needle always points to the north with one end, and the other to the south (which is why the ends or poles of the magnet were called north and south). The figure shows how to make sure that opposite poles of magnets attract, and like poles repel, just like electric charges.

Studying the magnet, they tried to divide it into parts in order to separate the poles. But nothing came of it. Any, the smallest piece always turned out to be a whole magnet with two poles. Why did it happen? Electricity helped to understand this.

You may have seen in a movie how steel machine parts are transferred at a factory. A thick round plate is lowered from above on chains, to which a bunch of parts stick. Then the plate with the parts is lifted and transferred to the desired place.

This is an electromagnet. Its main part is an iron coil made of wire. A current is sent through the wire, and the coil becomes a magnet.

Many turns of wire are wound in the coil of the electromagnet. But if you take just one turn and pass a current through it, you will also get an electromagnet, only a weak one. Even weaker, very tiny electromagnets, it turns out, are in everyone.

The one that revolves around the core is, as it were, an insignificant coil with current, which means it is a tiny magnet with two poles. There are other charged particles in the atom - protons. They also move and also form magnets.

But, everyone will ask, if there are magnets in any atom, then all substances must be magnets, not just iron.

It turns out that the whole point is how these tiny magnets are located. It is necessary that they be "disciplined" so that they can all turn to one side and keep the correct formation. Only then can matter become a magnet.

Only a few metals, especially iron, have such qualities. And recently, new, very strong magnets have appeared. They are even better than iron ones, although they are not made of metals, but of ferrites. If you ever hear this word, then know that it means new artificial magnetic substances.

If all the magnets suddenly disappeared, then the power plant would stop working, the radio would go silent, the televisions would go out, the telephone would not work, electric locomotives, subways, trams, trolleybuses, cars and buses would stop. Electronic devices and machines could not work, the whole modern technology... This is the role magnets play in people's lives.