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 from 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 original features: they are attracted to iron objects. The 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 assessed as a curious object.
Later, magnetite was used for navigation, finding that it tends to take a certain position when it is given the freedom to rotate. A scientific study 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, it was not possible to isolate one of the poles by cutting a fragment of magnetite in two - each separate fragment had its own pair of poles as a result.
According to today's ideas, the magnetic field permanent magnets is the resulting orientation of the electrons in the same direction. Only some types of materials interact with magnetic fields, a much smaller number of them are able to maintain 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 propagates in space and passes through objects (paper, wood);
- there is an increase in the MF intensity near the poles.
Permanent magnets support MT without external help. 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 magnetization 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 magnetically hard materials.
How a permanent magnet works
His work is related to 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 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 are heated at very high temperatures and are exposed to a strong external MF. 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 the domains align, reaching the magnetic saturation point. The material is then cooled and the aligned domains are locked into position. After the removal of the external MF, magnetically hard materials will retain most of their domains, creating a permanent magnet.
Characteristics of a permanent magnet
- The magnetic force is characterized by residual magnetic induction. Designated Br. This is the force that remains after the disappearance of the external MT. Measured in tests (Tl) or gauss (Gs);
- Coercivity or resistance to demagnetization - Ns. Measured in A / m. Shows what the intensity of the external MF should be in order to demagnetize the material;
- Maximum energy - BHmax. Calculated by multiplying the residual magnetic force Br and the coercivity Hc. Measured in MGSE (megagaussersted);
- The temperature coefficient of the residual magnetic force is Тс of Br. Characterizes the dependence of Br on the temperature value;
- Tmax is the highest temperature value at which permanent magnets lose their properties with the possibility of reverse recovery;
- Tcur is the highest temperature value at which the magnetic material permanently loses its properties. This indicator is called the Curie temperature.
The individual characteristics of a magnet change with temperature. At different meanings temperatures different types of magnetic materials work differently.
Important! All permanent magnets lose a percentage of magnetism as the temperature rises, but at a different rate depending on their type.
Types of permanent magnets
There are five types of permanent magnets in total, each of which is made differently based on materials with different properties:
- alnico;
- ferrites;
- rare earth SmCo based on cobalt and samarium;
- neodymium;
- polymeric.
Alnico
These are permanent magnets composed 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, however, 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
For the manufacture of 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 low production costs, resistance to heat (up to 250°C) and corrosion, ferrite magnets are one of the most popular for everyday use. They have greater internal coercivity than alnico, but less magnetic force than neodymium counterparts.
Application:
- sound speakers;
- security systems;
- large plate magnets to remove 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.
SmCo Rare Earth Magnets
Cobalt and samarium magnets operate over a wide temperature range, have high temperature coefficients and high corrosion resistance. This type retains its magnetic properties even at temperatures below absolute zero, making them popular for use in cryogenic applications.
Application:
- turbotechnics;
- pump couplings;
- wet environments;
- high temperature devices;
- miniature electric racing cars;
- electronic devices for operation in critical conditions.
Neodymium magnets
The strongest existing magnets, consisting of an alloy of neodymium, iron and boron. Thanks to them great strength, even miniature magnets are effective. This provides versatility of use. Each person is constantly next to 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, huge magnetic force and resistance to demagnetization, samples up to 1 mm can be produced.
Application:
- hard drives;
- sound-reproducing devices - microphones, acoustic sensors, headphones, loudspeakers;
- prostheses;
- magnetic coupling pumps;
- door closers;
- engines 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. They are used for unique devices where it is impossible to install solid analogues.
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 elements. They are made in standard forms: rings, rods, disks, and individual: trapezoids, arcs, etc. Due to the high iron content, neodymium magnets are susceptible to corrosion, therefore they are coated on top with nickel, stainless steel, teflon, titanium, rubber and other materials.
Video
To understand how to increase the strength of a magnet, you need to understand the process of magnetization. This will happen if the magnet is placed in an external magnetic field with the opposite side to the original one. An increase in the power of an electromagnet occurs when the current supply increases or the turns of the winding multiply.
You can increase the strength of the magnet using a standard set of necessary equipment: glue, a set of magnets (permanent ones are needed), a current source and an insulated wire. They will be needed to implement those methods of increasing the strength of the magnet, which are presented below.
Strengthening with a stronger magnet
This method consists in using a more powerful magnet to strengthen the original one. For implementation, it is necessary to place one magnet in an external magnetic field of another, which has more power. Electromagnets are also used for the same purpose. After holding the magnet in the field of another, amplification will occur, but the specificity lies in the unpredictability of the results, since such a procedure will work individually for each element.
Strengthening by adding other magnets
It is known that each magnet has two poles, and each attracts the opposite sign of other magnets, and the corresponding one does not attract, only repels. How to increase the power of a magnet using glue and additional magnets. Here it is supposed to add other magnets in order to increase the total power. After all, the more magnets, the correspondingly, there will be more force. The only thing to consider is the attachment of magnets with the same poles. In the process, they will repel, according to the laws of physics. But the challenge is to stick together despite the physical challenges. It is better to use glue that is designed for bonding metals.
Amplification method using the Curie point
In science there is the concept of the Curie point. Strengthening or weakening of the magnet can be done by heating or cooling it relative to this very point. So, heating above the Curie point or strong cooling (much below it) will lead to demagnetization.
It should be noted that the properties of a magnet during heating and cooling relative to the Curie point have a jump property, that is, having achieved the correct temperature, you can increase its power.
Method #1
If the question arose, how to make the magnet stronger if its strength is adjustable electric shock, then this can be done by increasing the current that is supplied to the winding. Here there is a proportional increase in the power of the electromagnet and the supply of current. The main thing is ⸺ gradual feed to prevent burnout.
Method #2
To implement this method, it is necessary to increase the number of turns, but the length must remain unchanged. That is, you can make one or two additional rows of wire so that the total number of turns becomes larger.
This section discusses ways to increase the strength of a magnet at home, for experiments you can order on the MirMagnit website.
Strengthening a conventional magnet
Many questions arise when ordinary magnets cease to perform their direct functions. This is often due to the fact that household magnets are not, in fact, they are magnetized metal parts that lose their properties over time. It is impossible to increase the power of such parts or return their properties that were originally.
It should be noted that attaching magnets to them, even more powerful ones, does not make sense, since, when they are connected by reverse poles, the external field becomes much weaker or even neutralized.
This can be checked with a regular household mosquito curtain, which should close in the middle with magnets. If more powerful ones are attached to the weak initial magnets from above, then as a result the curtain will generally lose the properties of the connection with the help of attraction, because the opposite poles neutralize each other's external fields on each side.
Experiments with neodymium magnets
Neomagnet is quite popular, its composition: neodymium, boron, iron. Such a magnet has a high power and is resistant to demagnetization.
How to strengthen neodymium? Neodymium is very susceptible to corrosion, that is, it rusts quickly, so neodymium magnets are plated with nickel to increase their service life. They also resemble ceramics, they are easy to break or split.
But there is no point in trying to increase its power artificially, because it is a permanent magnet, it has a certain level of strength for itself. Therefore, if you need to have a more powerful neodymium, it is better to purchase it, taking into account the desired strength of the new one.
Conclusion: the article discusses the topic of how to increase the strength of a magnet, including how to increase the power of a neodymium magnet. It turns out that there are several ways to increase the properties of a magnet. Because there is simply a magnetized metal, the strength of which cannot be increased.
Most simple ways: using glue and other magnets (they must be glued with identical poles), as well as a more powerful one, in the external field of which the original magnet must be located.
Methods for increasing the strength of an electromagnet are considered, which consist in additional winding with wires or intensifying the flow of current. The only thing to consider is the strength of the current flow for the safety and security of the device.
Ordinary and neodymium magnets are not able to succumb to an increase in their own power.
Transgeneration of electromagnetic field energy
Essence of research:
The main direction of research is the study of the theoretical and technical feasibility of creating devices that generate electricity due to the physical process of transgeneration of electromagnetic field energy discovered by the author. The essence of the effect lies in the fact that when adding electromagnetic fields (constant and variable), not energies are added, but field amplitudes. The field energy is proportional to the square of the amplitude of the total electromagnetic field. As a result, with a simple addition of fields, the energy of the total field can be many times greater than the energy of all the initial fields separately. This property of the electromagnetic field is called the non-additivity of the field energy. For example, when adding three flat disk permanent magnets into a stack, the energy of the total magnetic field increases nine times! A similar process occurs during the addition of electromagnetic waves in feeder lines and resonant systems. The energy of the total standing electromagnetic wave can be many times greater than the energy of the waves and the electromagnetic field before addition. As a result, the total energy of the system increases. The process is described by a simple field energy formula:
When adding three permanent disk magnets, the volume of the field decreases by a factor of three, and the volumetric energy density of the magnetic field increases by a factor of nine. As a result, the energy of the total field of the three magnets together turns out to be three times the energy of the three disconnected magnets.
When adding electromagnetic waves in one volume (in feeder lines, resonators, coils, there is also an increase in the energy of the electromagnetic field compared to the original one).
The electromagnetic field theory demonstrates the possibility of energy generation due to the transfer (trans-) and addition of electromagnetic waves and fields. The theory of energy transgeneration of electromagnetic fields developed by the author does not contradict classical electrodynamics. The idea of a physical continuum as a superdense dielectric medium with a huge latent mass energy leads to the fact that physical space has energy and transgeneration does not violate the full law of conservation of energy (taking into account the energy of the medium). The non-additivity of the energy of the electromagnetic field demonstrates that for an electromagnetic field, the simple fulfillment of the law of conservation of energy does not occur. For example, in the theory of the Umov-Poynting vector, the addition of the Poynting vectors leads to the fact that the electric and magnetic fields are added simultaneously. Therefore, for example, when adding three Poynting vectors, the total Poynting vector increases by a factor of nine, and not three, as it seems at first glance.
Research results:
The possibility of obtaining energy by adding electromagnetic waves of research was investigated experimentally in various types of feeder lines - waveguides, two-wire, strip, coaxial. The frequency range is from 300 MHz to 12.5 GHz. Power was measured both directly - by wattmeters, and indirectly - by detector diodes and voltmeters. As a result, when performing certain settings in the feeder lines, positive results were obtained. When adding the amplitudes of the fields (in loads), the allocated power in the load exceeds the power supplied from different channels (power dividers were used). The simplest experiment illustrating the principle of amplitude addition is an experiment in which three narrowly directed antennas operate in phase on one receiver, to which a wattmeter is connected. The result of this experience: the power recorded at the receiving antenna is nine times greater than each transmitting antenna individually. At the receiving antenna, the amplitudes (three) from the three transmitting antennas are added, and the receive power is proportional to the square of the amplitude. That is, when adding three common-mode amplitudes, the receiving power increases nine times!
It should be noted that interference in air (vacuum) is multiphase, differs in a number of ways from interference in feeder lines, cavity resonators, standing waves ah in coils, etc. In the so-called classical interference pattern, both addition and subtraction of the amplitudes of the electromagnetic field are observed. Therefore, in general, in case of multiphase interference, the violation of the energy conservation law is of a local nature. In a resonator or in the presence of standing waves in feeder lines, the superposition of electromagnetic waves is not accompanied by a redistribution of the electromagnetic field in space. In this case, in a quarter and half-wave resonators, only the addition of the field amplitudes occurs. The energy of the waves combined in one volume comes from the energy that has passed from the generator into the resonator.
Experimental studies fully confirm the theory of transgeneration. It is known from microwave practice that even with a normal electrical breakdown in feeder lines, the power exceeds the power supplied from the generator. For example, a waveguide designed for a microwave power of 100 MW is pierced by adding two microwave powers of 25 MW each - by adding two counterpropagating microwave waves in the waveguide. This can happen when microwave power is reflected from the end of the line.
A number of original circuit diagrams to generate energy using various types interference. The main frequency range is meter and decimeter (UHF), up to centimeter. On the basis of transgeneration, it is possible to create compact autonomous sources of electricity.
a) General information. To create a constant magnetic field in a number of electrical devices, permanent magnets are used, which are made of magnetically hard materials with a wide hysteresis loop (Fig. 5.6).
The work of a permanent magnet occurs in the area from H=0 before H \u003d - H s. This part of the loop is called the demagnetization curve.
Consider the basic relationships in a permanent magnet, which has the shape of a toroid with one small gap b(fig.5.6). Owing to the shape of a toroid and a small gap, stray fluxes in such a magnet can be neglected. If the gap is small, then the magnetic field in it can be considered uniform.
Fig.5.6. Permanent Magnet Demagnetization Curve
If buckling is neglected, then the induction in the gap AT & and inside the magnet AT are the same.
Based on the total current law in closed-loop integration 1231 rice. we get:
Fig.5.7. Permanent magnet shaped like a toroid
Thus, the field strength in the gap is directed opposite to the field strength in the magnet body. For a DC electromagnet having a similar shape of the magnetic circuit, without taking into account saturation, you can write:.
Comparing it can be seen that in the case of a permanent magnet n. c, which creates a flow in the working gap, is the product of the tension in the magnet body and its length with the opposite sign - Hl.
Taking advantage of the fact that
, (5.29)
, (5.30)
where S- the area of the pole; - conductivity of the air gap.
The equation is the equation of a straight line passing through the origin in the second quadrant at an angle a to the axis H. Given the scale of induction t in and tension t n angle a is defined by the equality
Since the induction and strength of the magnetic field in the body of a permanent magnet are connected by a demagnetization curve, the intersection of this straight line with the demagnetization curve (point BUT in Fig.5.6) and determines the state of the core at a given gap.
With a closed circuit and
With growth b conductivity of the working gap and tga decrease, the induction in the working gap decreases, and the field strength inside the magnet increases.
One of the important characteristics of a permanent magnet is the energy of the magnetic field in the working gap W t . Considering that the field in the gap is uniform,
Substituting value H we get:
, (5.35)
where V M is the volume of the magnet body.
Thus, the energy in the working gap is equal to the energy inside the magnet.
Product dependency B(-H) in the induction function is shown in Fig.5.6. Obviously, for point C, where B(-H) reaches its maximum value, the energy in the air gap also reaches its maximum value, and from the point of view of using a permanent magnet, this point is optimal. It can be shown that the point C corresponding to the maximum of the product is the point of intersection with the beam demagnetization curve OK, through a point with coordinates and .
Let us consider in more detail the influence of the gap b by the amount of induction AT(fig.5.6). If the magnetization of the magnet was carried out with a gap b, then after the removal of the external field in the body of the magnet, an induction will be established corresponding to the point BUT. The position of this point is determined by the gap b.
Decrease the gap to the value , then
. (5.36)
With a decrease in the gap, the induction in the magnet body increases, however, the process of changing the induction does not follow the demagnetization curve, but along the branch of a private hysteresis loop AMD. Induction AT 1 is determined by the point of intersection of this branch with a ray drawn at an angle to the axis - H(dot D).
If we increase the gap again to the value b, then the induction will drop to the value AT, and dependence B (H) will be determined by the branch DNA private hysteresis loop. Usually partial hysteresis loop AMDNA narrow enough and replaced by a straight AD, which is called the return line. The slope to the horizontal axis (+ H) of this line is called the return coefficient:
. (5.37)
The demagnetization characteristic of a material is usually not given in full, but only the saturation induction values are given. B s , residual induction In g, coercive force N s. To calculate a magnet, it is necessary to know the entire demagnetization curve, which for most magnetically hard materials is well approximated by the formula
The demagnetization curve given by (5.30) can be easily plotted graphically if one knows B s , B r .
b) Determination of the flow in the working gap for a given magnetic circuit. In a real system with a permanent magnet, the flow in the working gap differs from the flow in the neutral section (in the middle of the magnet) due to the presence of stray and buckling flows (Fig.).
The flow in the neutral section is equal to:
, (5.39)
where is the flow in the neutral section;
Bulging flow at the poles;
Flux scattering;
workflow.
The scattering coefficient o is determined by the equality
If we accept that flows 
created by the same magnetic potential difference, then
. (5.41)
We find the induction in the neutral section by defining:
,
and using the demagnetization curve Fig.5.6. The induction in the working gap is equal to:
since the flow in the working gap is several times less than the flow in the neutral section.
Very often, the magnetization of the system occurs in an unassembled state, when the conductivity of the working gap is reduced due to the absence of parts made of ferromagnetic material. In this case, the calculation is carried out using a direct return. If the leakage fluxes are significant, then the calculation is recommended to be carried out by sections, as well as in the case of an electromagnet.
Stray fluxes in permanent magnets play a much greater role than in electromagnets. The fact is that the magnetic permeability of hard magnetic materials is much lower than that of soft magnetic materials, from which systems for electromagnets are made. Stray fluxes cause a significant drop in the magnetic potential along the permanent magnet and reduce n. c, and hence the flow in the working gap.
The dissipation coefficient of the completed systems varies over a fairly wide range. The calculation of the scattering coefficient and scattering fluxes is associated with great difficulties. Therefore, when developing a new design, it is recommended to determine the value of the scattering coefficient on a special model in which the permanent magnet is replaced by an electromagnet. The magnetizing winding is chosen so as to obtain the necessary flux in the working gap.
Fig.5.8. Magnetic circuit with a permanent magnet and leakage and buckling fluxes
c) Determining the dimensions of the magnet according to the required induction in the working gap. This task is even more difficult than determining the flow with known dimensions. When choosing the dimensions of a magnetic circuit, one usually strives to ensure that the induction At 0 and tension H 0 in the neutral section corresponded to the maximum value of the product N 0 V 0 . In this case, the volume of the magnet will be minimal. The following recommendations are given for the choice of materials. If it is required to obtain a large value of induction at large gaps, then the most suitable material is magnico. If it is necessary to create small inductions with a large gap, then alnisi can be recommended. With small working gaps and a large value of induction, it is advisable to use an alni.
The cross section of the magnet is selected from the following considerations. The induction in the neutral section is chosen equal to At 0 . Then the flow in the neutral section
,
where is the cross section of the magnet
.
Induction values in the working gap In r and the area of the pole are given values. The most difficult is to determine the value of the coefficient scattering. Its value depends on the design and induction in the core. If the cross section of the magnet turned out to be large, then several magnets connected in parallel are used. The length of the magnet is determined from the condition for creating the necessary NS. in the working gap with tension in the body of the magnet H 0:
where b p - the value of the working gap.
After choosing the main dimensions and designing the magnet, a verification calculation is carried out according to the method described earlier.
d) Stabilization of the characteristics of the magnet. During the operation of the magnet, a decrease in the flow in the working gap of the system is observed - the aging of the magnet. There are structural, mechanical and magnetic aging.
Structural aging occurs due to the fact that after hardening of the material, internal stresses arise in it, the material acquires an inhomogeneous structure. In the process of work, the material becomes more homogeneous, internal stresses disappear. In this case, the residual induction In t and coercive force N s decrease. To combat structural aging, the material is subjected to heat treatment in the form of tempering. In this case, internal stresses in the material disappear. Its characteristics become more stable. Aluminum-nickel alloys (alni, etc.) do not require structural stabilization.
Mechanical aging occurs with shock and vibration of the magnet. In order to make the magnet insensitive to mechanical influences, it is subjected to artificial aging. The magnet specimens are subjected to such shocks and vibrations as are encountered in operation before installation in the apparatus.
Magnetic aging is a change in the properties of a material under the influence of external magnetic fields. A positive external field increases the induction along the return line, and a negative one reduces it along the demagnetization curve. In order to make the magnet more stable, it is subjected to a demagnetizing field, after which the magnet operates on a return line. Due to the lower steepness of the return line, the influence of external fields is reduced. When calculating magnetic systems with permanent magnets, it must be taken into account that in the process of stabilization, the magnetic flux decreases by 10-15%.
