If the magnet, they are no strangers. Many household appliances are on the top, and they are taken from some used speakers to make toys. But when it comes neodymium iron boron or material, you must feel confused and incomprehensible. The following is an explanation of the past and present of the magnet, so that you have a deep understanding of the magnet.

Chinese name: main components of magnet: iron, cobalt , nickel, etc.

Foreign name: Magnet

A magnet is an object that can attract and generate a magnetic field outside of it. A narrow magnet refers to a product of magnetite ore, and a generalized magnet refers to an object or device that is used to generate a magnetic field. As a magnetic dipole magnet to attract a ferromagnetic substance, such as metallic iron, nickel and cobalt. The determination of the magnetic pole is to hang a magnet with a thin wire, and the magnetic pole pointing to the north is called the north pole or the north pole, and the magnetic pole pointing to the south is the guide pole or the S pole. (If you think of the earth as a magnet, the earth's geomagnetic north pole is the S pole, and the geomagnetic south pole is the N pole.) The magnets are attracted to each other and the same poles are repelled. The guide is extremely attracted to the North Pole, and the guide is extremely repulsive to the guide, referring to the repelling of the North Pole and the North Pole.

The magnets are divided into permanent magnets and non-permanent magnets. Natural permanent magnets are also known as natural magnets, and permanent magnets can also be made by hand (the strongest magnet is a neodymium magnet). Non-permanent magnets are only magnetic under certain conditions, usually in the form of electromagnets, that is, using current to strengthen their magnetic field.

The magnetic molecules (molecular magnetism) inside the unmagnetized magnet are randomly arranged, and the magnetic molecules will be regularly arranged after the magnetization process. At this time, the magnetic poles of the magnetic molecules and the S poles are magnetized in the same direction to become magnets. At the same time, there are opposite poles on the same magnet and the magnetic quantities of the two poles are equal.

Magnetic magnet

Magnets generate magnetic fields that attract ferromagnetic materials such as metals such as iron, nickel, and cobalt. Hang the midpoint of the strip magnet with a thin wire, and the magnet at rest

At the same time, its two ends point to the south and north of the earth, the end pointing to the north is referred to as the north pole or the north pole, and the end pointing to the south is the guide pole or the S pole. If you think of the earth as a large magnet, the current geomagnetic North Pole is the guide pole, and the geomagnetic South Pole is the North Pole. Between the magnet and the magnet, the same pole repels and the opposite pole attracts. Therefore, the compass is repelled from the South Pole, the North Arrow is repelled from the North Pole, and the compass is attracted to the North Pole.

Classification of magnets

Magnets can be divided into "Permanent Magnets" and "non-permanent magnets." The permanent magnet can be a natural product, also known as a natural magnet, or it can be made by hand (the strongest magnet is a neodymium iron boron magnet). Non-permanent magnets, such as electromagnets, only exhibit magnetism under certain conditions.

definition

Magnets, which should be called magnetic steel, English: Magnet, magnetic steel now mainly divided into two categories, one is Soft Magnets, the other is Hard Magnets.

concept

Soft magnetic includes silicon steel sheet and soft magnetic core; hard magnetic includes aluminum nickel cobalt, samarium cobalt, ferrite and neodymium iron boron. Among them, the most expensive is samarium cobalt magnet, the cheapest is ferrite magnet. The highest performance is NdFeB magnet, but the performance is the most stable. The best temperature coefficient is AlNiCo magnet. Users can choose different hard magnetic products according to different needs.

The magnets we refer to are generally referred to as permanent magnets.

Permanent magnets are divided into two major categories.

First class

Metal alloy magnets include neodymium iron boron magnets Nd2Fe14B), samarium cobalt magnets (SmCo), alnico magnets (ALNiCO)

Second category

Ferrite Permanent Magnets

1. Neodymium iron boron magnet It is the magnet with the highest commercialization performance. It is called magnetic king and has a very high magnetic performance. Its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite. Its mechanical processing performance is also quite good. Operating temperatures up to 200 degrees Celsius. Moreover, its texture is hard, its performance is stable, and it has a good cost performance, so its application is extremely extensive. However, because of its strong chemical activity, it must be treated with a surface coating. (such as Zn, Ni, electrophoresis, passivation, etc.).

2. Ferrite magnets The main raw materials include BaFe12O19 and SrFe12O19. It is made of ceramic technology and has a relatively hard texture. It is a brittle material. Because ferrite magnets have good temperature resistance, low price and moderate performance, they have become the most widely used permanent magnets.

3. Aluminium-nickel-cobalt magnet is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. The casting process can be processed into different sizes and shapes, and the processability is very good. Cast AlNiCo permanent magnets have the lowest reversible temperature coefficient and can operate at temperatures above 600 degrees Celsius. AlNiCo permanent magnet products are widely used in various instrumentation and other applications.

4. Samarium Cobalt (SmCo) is classified into SmCo5 and Sm2Co17 depending on the composition. Its development is limited due to the high price of its materials. Samarium Cobalt (SmCo), as a rare earth permanent magnet, has a high magnetic energy product (14-28 MGOe), reliable coercivity and good temperature characteristics. Compared with neodymium iron boron magnets, samarium cobalt magnets are more suitable for working in high temperature environments.

Permanent Magnets

The permanent magnet can be a natural product, also known as a natural magnet, or it can be made by hand (the strongest magnet is a neodymium iron boron magnet).

Non-permanent magnet

When a non-permanent magnet is heated to a certain temperature, it will suddenly lose its magnetic properties. This is because the arrangement of many "meta-magnets" that make up the magnet is caused by order to disorder; the magnet that loses magnetism is placed in the magnetic field when the magnetization is When a certain value is reached, it is magnetized again, and the arrangement of "meta magnets" is from disorder to order.

Artificial magnet

Artificial magnets: divided into hoof magnets and strip magnets, are the most common in everyone's life, and hoof magnets are popular. Refers to the side of one surface of the magnet is magnetic, the other surface of the magnetic weaker magnets, with zinc-plated metal is specially treated to wrap double-sided magnet side, thus wrapping the magnetic side is shielded, the magnetic force to the other side is refracted On the other side, the magnetism will be enhanced. If there are occasions, only one side is magnetic, and the other side may cause damage or interference if it is magnetic; in some cases, the magnet on the box only needs one side to be magnetic, the other side may or may not be magnetic, and it is useless. This use of single-sided magnetics will greatly reduce costs and save magnetic materials. The magnetic refraction of a single-sided magnet is like the refraction of a signal by a satellite pot or the refraction of light by a flashlight. The refraction effect is determined by the following three aspects: 1. Material: material selection and thickness, and the distance between the magnet and the material is close. Relationship. Pure iron is easy to leak magnetic, and the refraction will be enhanced after special treatment, but the 100% shielding material has not been studied, but the materials made by different manufacturers have different effects.

Angle: According to the principle of refraction, the curved material has the best effect, and the right angle material has a large loss of refraction.

Space: The magnetic lines of force are like mobile phone signals in the air, and need space to reflect them. If the flashlight lamp pot is completely wrapped in the lamp, the effect is definitely not good, because a large amount of light refraction is lost.

How to use the above principle, the best effect of magnetic enhancement, is the best problem between many parameters, many manufacturers are also doing experiments repeatedly, such as the ideal result of single-sided magnetic processing of Xi'an Guotai Magnet Factory is enhanced by 50% In this way, in the field of packaging boxes and the like, the production cost will be greatly reduced and the magnetic material can be saved.

Neodymium iron boron magnet

Neodymium magnet, also known as neodymium iron magnet, has a chemical formula of Nd2Fe14B, which is an artificial permanent magnet and has the strongest permanent magnet for magnetization.

Known as the magnetic king, it has extremely high magnetic properties and its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite. Its mechanical processing performance is also quite good. Operating temperatures up to 200 degrees Celsius. Moreover, its texture is hard, its performance is stable, and it has a good cost performance, so its application is extremely extensive. However, because of its strong chemical activity, it must be treated with a surface coating. (such as Zn, Ni, electrophoresis, passivation, etc.).

The neodymium magnet was invented in 1982 by Sagawa Mori and others of Sumitomo Special Metals Co., Ltd., and its chemical formula is mainly composed of chemical elements such as bismuth, iron and boron. It is possible to replace the traditional iron magnets in many fields, Alnico magnet such as samarium cobalt and motors, instrumentation and equipment, automobile industry, petrochemical industry and magnetic health care products. Can produce a variety of shapes: such as disc magnets, ring magnets, rectangular magnets, arc magnets and other shapes of magnets.

Neodymium magnets with strong magnetic properties are widely used in electronic products such as hard disks, mobile phones, headphones, and the like.

Main ingredient

A magnet, also known as a magnet, refers to an object or material that has a magnetic field around and within itself. It is divided into two categories, natural and artificial. Artificial magnets are usually made of a metal alloy and have strong magnetism. It can also be divided into "permanent magnets" and "non-permanent magnets", namely "hard magnetic" and "soft magnetic". The main component of natural magnet: triiron tetroxide, chemical formula Fe3O4, often called "magnetic iron oxide". A black crystal with magnetic properties. It can be regarded as a compound composed of ferrous oxide and iron oxide. Because there are two different valence ions in the crystal of ferroferric oxide, one third of them are Fe2+ and two thirds are Fe3+, which is a complex compound. It is insoluble in water and does not react with water. Reacts with acid and is insoluble in alkali. Primarily used in the manufacture of primers and topcoats, magnetic materials for the electronics industry, and rust inhibitors for the construction industry.

The magnetic size is arranged as

NdFeB magnets, samarium cobalt magnets, AlNiCo magnets, ferrite magnets.

performance

definition

There are three main performance parameters to determine the performance of the magnet:

Remanence Br: When the permanent magnet is magnetized to the technical saturation and the external magnetic field is removed, the retained Br is called the residual magnetic induction.

Coercive force Hc: The B of the permanent magnet magnetized to the technical saturation is reduced to zero, and the added reverse magnetic field strength is called the magnetic coercive force.

Coercivity

The magnetic energy product BH: represents the magnetic energy density established by the magnet in the air gap space (the two magnetic pole spaces of the magnet), that is, the magnetostatic energy per unit volume of the air gap. Since this energy is equal to the product of the Bm and Hm of the magnet, it is called the magnetic energy product.

Magnetic field: The space that magnetically acts on the magnetic pole is a magnetic field.

Surface magnetic field: The magnetic induction at a specified position on the surface of a permanent magnet.

Antimagnetic

Antimagnetic is a magnetic phenomenon in which some classes of substances, when placed in an external magnetic field, have a weak repulsion to the magnetic field.

Paramagnetic

Paramagnetic refers to the magnetic state of a material. Some materials can be affected by an external magnetic field, producing characteristics of magnetization vectors that are in the same direction. Such materials have a positive magnetic susceptibility. The opposite of paramagnetic is called diamagnetism.

Ferromagnetic

Ferromagnetic refers to the magnetic state of a material with a spontaneous magnetization phenomenon. Among the materials, iron is the most widely known, hence the name.

Some materials are magnetized by the action of an external magnetic field, and even if the external magnetic field disappears, the magnetization state can be maintained and magnetic, that is, a so-called spontaneous magnetization phenomenon. All permanent magnets are ferromagnetic or ferrimagnetic.

Basically the concept of ferroma includes any substance that exhibits magnetism when there is no external magnetic field. This concept is still used this way. But through a deeper understanding of the different magnetic materials and their magnetic properties, scholars have made a more precise definition of this concept. It is said to be ferromagnetic when all the magnetic ions in the original cell of a substance point in its magnetic direction. If only a part of the magnetic field of the ion is directed to its magnetic direction, it is called ferrimagnetic. If the direction of the magnetic ions is exactly offset by each other (although all magnetic ions point only in two opposite directions), it is called antiferromagnetic.

The magnetic phenomenon of a substance has a critical temperature at which it occurs. For ferromagnetic and ferrimagnetic materials, this temperature is called the Curie temperature; for antiferromagnetic materials, this temperature is called the Neil temperature.

Some people think that the attraction between magnets and ferromagnetic materials is the earliest human understanding of magnetism.

Select magnet

Before deciding which magnet to choose, should you clearly know what role the magnet needs? Magnet (magnet)

Main role: moving objects, fixing objects or lifting objects.

The shape of the required magnet: a disk shape, a circular shape, a square shape, a tile shape or a special shape.

The size of the required magnet: length, width, height, diameter and tolerance, etc.

The suction of the required magnet, the expected price and quantity, and so on.

The compass is invented according to the nature of the magnet.

effect

Physical effect

1. Guide North

2. Attract light and small objects

3. Electromagnet can be used as an electromagnetic relay

4. Motor

5. Generator

6. Electroacoustic

7. Magnetic therapy

8. Magnetic levitation

9. Nuclear Magnetic Resonance

Therapeutic effect

The magnet is salty and salty, and it is flat; it is liver and kidney;

It has the functions of calming the liver and yang, clearing the eyes and clearing the eyes, calming the nerves and calming the nerves.

Indications for liver and vertigo, convulsions, insomnia, fainting, tinnitus and deafness, kidney deficiency and asthma.

Manufacture of magnets

Some substances can be rubbed into magnets, the material is not iron, or steel, but not all steel can be made into magnets, because they contain their substances, stainless steel can not act as a magnet.

Now let's make magnets, magnets and a screwdriver. It's the material you need. Use a magnet to rub the metal part of the screwdriver. From one end to the other, they rub repeatedly to create a magnetic screwdriver. .

Orientation direction

concept

Most magnetic materials can be magnetized to saturation in the same direction, a direction called "magnetization direction" (orientation direction). A magnet that has no orientation direction (also called an isotropic magnet) is much weaker than an orientation magnet (also called an anisotropic magnet).

North and South pole definition of magnet

magnet

"Arctic" is defined as the north pole of the earth pointing to the north pole of the earth after the magnet rotates freely, referred to as "N". Similarly, the south pole of the magnet also points to the south pole of the earth, referred to as "S".

Safe handling and storage of magnets

Always be very careful, as the magnets will stick together and may pinch your fingers. When the magnets are attracted to each other, the magnet itself may be damaged by the collision (the corners are knocked off or the cracks are knocked out).

Keep magnets away from items that are easily magnetized, such as floppy disks, credit cards, computer monitors, watches, mobile phones, medical devices, etc.

Keep the magnet away from the pacemaker. magnet

For larger magnets, plastic or cardboard spacers should be placed between each piece to ensure that the magnets can be easily separated.

The magnet should be stored in a dry, constant temperature environment as much as possible.

Magnetic separation

Only materials that can be attracted to the magnet can function to block the magnetic field, and the thicker the material, the better the magnetic separation effect.

Strongest magnet

At present, the highest performance magnet is a rare earth magnet, and in the rare earth magnet, neodymium iron boron is the most powerful magnet. However, in the environment above 200 degrees Celsius, samarium cobalt is the most powerful magnet.

How to determine the size of the magnetic force of the magnet

Why does the magnet have a magnetic force, that is, the earth's magnetic field and current will be strongly combined due to the rotation of the earth, and finally the whole earth becomes a large magnetic field. Minerals such as nickel, cobalt, and iron on Earth rotate as the Earth rotates, turning it into a natural magnet.

Everyone knows that there is a gravitational field between the substances. Similar to a magnetic field, it is a field that fills the space around the pole. The size of the magnetic field can be represented by the number of imaginary magnetic lines of force. The denser the magnetic field lines are the stronger the magnetic field, and the weaker the magnetic field is.

application

Application in traditional industries

When we talk about the magnetic source of magnetic materials, electromagnetic induction, and magnetic devices, we have already mentioned some magnetic material electromagnets.

Practical application. In fact, magnetic materials have been widely used in various aspects of traditional industries.

For example, if there is no magnetic material, electrification becomes impossible, because generators are used for power generation, transformers are used for power transmission, and speakers are used for electric machines, telephones, radios, and televisions. Magnetic steel coil structures are used in many instruments. These have already been said when talking about other content.

Magnet in medical applications

Pigeon fans know that if they fly to hundreds of kilometers, they will automatically return home. Why do pigeons have such a good reputation? Originally, pigeons are sensitive to the Earth's magnetic field, and they can use the changes in the Earth's magnetic field to find their home. If a magnet is attached to the head of the pigeon, the pigeon will be lost. If the pigeons fly over the radio tower, strong electromagnetic interference can also make them lose their way. magnet

In medicine, the use of nuclear magnetic resonance can diagnose abnormal tissue and determine disease. This is our familiar MRI technology. The basic principle is as follows: the nucleus has positive electricity and spin motion. Usually, the arrangement of the spin axis of the nucleus is irregular, but when it is placed in an external magnetic field, the spatial orientation of the nuclear spin transitions from disorder to order. The magnetization vector of the spin system gradually increases from zero, and when the system reaches equilibrium, the magnetization reaches a stable value. If the nuclear spin system is subjected to external influences at this time, the RF excitation of the nucleus at a certain frequency can cause a resonance effect. After the RF pulse is stopped, the atomic nucleus that has been excited by the spin system cannot maintain this state, will return to the original arrangement state in the magnetic field, and release weak energy, become a radio signal, detect many signals, and make At the time of spatial resolution, an image of the distribution of nuclei in motion is obtained. Nuclear magnetic resonance is characterized by the fact that flowing liquid does not produce a signal called a flow effect or a flow blank effect. Thus the blood vessel is a gray-white tubular structure and the blood is black with no signal. This makes the blood vessels easy to separate from soft tissue. Surrounded by cerebrospinal fluid around the normal spinal cord, the cerebrospinal fluid is black, and the white dura mater is set off by fat, making the spinal cord appear as a strong white signal structure. Nuclear magnetic resonance has been applied to imaging diagnosis of various systems throughout the body. The best effect is the brain, its spinal cord, large blood vessels, joint bones, soft tissues and pelvis. Cardiovascular disease can not only observe the anatomical changes of each chamber, large blood vessels and valves, but also can be used for ventricular analysis, qualitative and semi-quantitative diagnosis, can be used as multiple cut charts, high spatial resolution, showing the whole heart and lesions And its relationship with surrounding structures, superior to other X-ray imaging, two-dimensional ultrasound, radionuclide and CT examination. magnet

Magnetic can not only diagnose, but also help treat diseases. Magnet is a medicinal herb of ancient Chinese medicine. Nowadays, people use the magnetic difference between different components in the blood to separate red blood cells and white blood cells. In addition, the interaction between the magnetic field and the body's meridians can achieve magnetic therapy, and has a unique role in the treatment of a variety of diseases, including magnetic therapy pillows, magnetic therapy belts and other applications. The iron remover made of magnet can remove the iron powder which may exist in the flour, etc. The magnetized water can prevent the boiler from scaling, and the magnetized seed can increase the yield of the crop to a certain extent.

Magnetic applications in astronomy and other fields

We already know that the earth is a huge magnet, how does it relate to geological conditions? What is the magnetic field in the universe?

At least on the picture we have seen the brilliant Northern Lights. China has recorded the Northern Lights since ancient times. The Northern Lights are actually the result of the interaction of particles in the solar wind and the Earth's magnetic field. The solar wind is a stream of energetic charged particles emitted by the sun. When they reach the Earth, they interact with the Earth's magnetic field, just as the current-carrying wires are forced in the magnetic field, causing these particles to move and accumulate in the north and south poles, and collide with the thin gas at high altitudes, resulting in gas. The molecules are excited to illuminate.

Sunspots are areas where the magnetic field on the sun is very intense. The outbreak of sunspots has an impact on our lives, such as the temporary interruption of radio communications. Therefore, studying sunspots is important to us.

Geomagnetic changes can be used to explore deposits. Since all materials have strong or weak magnetic properties, if they come together to form a deposit, they will inevitably interfere with the geomagnetic field in the nearby area, causing anomalies in the geomagnetic field. According to this, the magnetism of the earth can be measured on land, in the ocean or in the air, and the geomagnetic map can be obtained. The analysis and further exploration of the magnetic field anomaly on the geomagnetic map can often reveal unknown mineral deposits or special geological structures.

Rocks of different geological ages often have different magnetic properties. Therefore, it is possible to judge the change of geological time and the change of the crust according to the magnetic assistance of the rock.

Many mineral resources are symbiotic, that is to say, several minerals are mixed together, and they have different magnetic properties. Using this feature, people have developed a magnetic separator that uses different magnetisms of different minerals and the difference in magnetic strength to attract these materials with magnets. Then they are different in attractiveness, and the results can be mixed together. Different magnetic minerals are separated to achieve magnetic beneficiation .

Magnetic applications in the military field

Magnetic materials are also widely used in the military field. For example, ordinary mines or mines can only explode when they touch a target, so the effect is limited. If magnetic sensors are installed on mines or mines, because tanks or warships are made of steel, the sensors can detect changes in the magnetic field to explode mines or mines when they are close (without touching the target), increasing the lethality.

In modern warfare, air supremacy is one of the keys to winning the battle. However, the aircraft is easily detected by the enemy's radar during the flight, which is of great danger. In order to avoid the monitoring of enemy radar, a special magnetic material-absorbent material can be coated on the surface of the aircraft, which can absorb the electromagnetic waves emitted by the radar, so that the radar electromagnetic waves rarely reflect, so the enemy radar can not detect the radar echo. The aircraft could not be found, which made the aircraft invisible. This is the famous "stealth aircraft." Stealth technology is a hot spot in the world of military research. The US F117 stealth fighter is an example of the successful use of stealth technology.

In the "Star Wars" program in the United States, there is a research and development of a new type of weapon "electromagnetic weapons." The traditional artillery guns use the thrust generated by the instantaneous expansion of the ammunition to accelerate the projectile quickly and launch the cannon. The electromagnetic gun puts the projectile in the solenoid and energizes the solenoid. Then the magnetic field generated by the solenoid will generate a huge driving force for the projectile, and the projectile will be fired. This is the so-called electromagnetic gun. Similar to electromagnetic missiles.

Craftsmanship

Process

The production process of neodymium iron boron magnets, samarium cobalt magnets, alnico magnets, and ferrite magnets is also different. From the technology, there are sintered NdFeB magnets and bonded NdFeB magnets. We mainly talk about sintered NdFeB magnets.

Process flow

Ingredients → Smelting ingot → Pulverizing → Pressing → Sintering and tempering → Magnetic detection → Grinding → Pin cutting → Plating → Finished product. The ingredients are the basis, and the sintering and tempering is the key production tool of NdFeB magnets: smelting furnace, E-breaking machine, ball mill , jet mill, press forming machine, vacuum packaging machine, isostatic press, sintering furnace, heat treatment vacuum furnace, Magnetic performance tester, Gauss meter.

NdFeB magnet processing tool

There are special slicer, wire cutting machine, flat mill, double-sided machine, punching machine, chamfering machine, electroplating equipment.

Industrial application

Maglev train application

Maglev train is a magnetic levitation high-speed magnetic levitation train using a contactless electromagnetic suspension, guidance and drive system

Car system. It can reach more than 500 kilometers per hour. It is the fastest ground passenger transport vehicle in the world. It has the advantages of fast speed, strong climbing ability, low energy consumption, low noise, safe and comfortable, no fuel, less pollution, and low price. . And it uses an elevated way, occupying very little cultivated land. Maglev trains mean that these trains use the basic principle of magnetism to float on the rails instead of the old steel and rail trains. The magnetic levitation technology uses electromagnetic force to lift the entire train compartment, freeing from the unpleasant friction and unpleasant humming, and achieving a fast "flight" with no contact with the ground and no fuel.

The maglev train is the most fundamental breakthrough in railway technology since the introduction of Stephenson's "Rocket" steam locomotive about 200 years ago. The maglev train seems to be a new thing today, but its theoretical preparation has a long history. The study of magnetic levitation technology originated in Germany. As early as 1922, German engineer Hermann Kemper proposed the principle of electromagnetic levitation. In 1934, he applied for the patent of maglev train. After the 1970s, with the strengthening of the economic strength of the industrialized countries in the world, in order to improve the transportation capacity to meet the needs of its economic development, developed countries such as Germany, Japan, the United States, Canada, France, and the United Kingdom have begun planning for the magnetic levitation transportation system. Development.

Application of NdFeB

At present, the application of NdFeB magnets in China is as follows. 37% of applications in high-tech products, such as magnetic resonance imaging (MRI), mobile phone vibration, hard disk drive voice coil (VCM), optical disk (DVD, CD-ROM) drive spindle , electric tools, electric vehicles, inverter air conditioner engines. Traditional medium and low-end products account for 63% of applications, such as audio devices, magnetic adsorption devices, magnetic separators, and magnetizers.

Electromagnet definition

A device with a core inside and a magnetic coil like a magnet is called an electromagnet. Usually made into strips or hooves. The iron core is made of soft iron or silicon steel which is easily magnetized and easily disappears. Such an electromagnet is magnetic when energized, and disappears after being powered off. Electromagnets are extremely widely used in everyday life. The invention of the electromagnet also greatly improved the power of the generator.

application

Electromagnets are extremely widely used in everyday life. Electromagnets are an application of current magnetic effects (electro-magnetic) and are closely related to life, such as electromagnetic relays, electromagnetic cranes, maglev trains, etc. Electromagnets can be divided into two types: DC electromagnets and AC electromagnets. If the electromagnets are divided according to the purpose, they can be mainly divided into the following five types: (1) Traction electromagnets - mainly used to pull mechanical devices, open or close various valves to perform automatic control tasks. (2) Lifting electromagnets - used as lifting devices to lift ferromagnetic materials such as steel ingots, steel, and iron sand. (3) Brake electromagnet - mainly used to brake the motor to achieve accurate parking. (4) Electromagnetic systems of automatic electrical appliances - such as electromagnetic systems of electromagnetic relays and contactors, electromagnetic trips of automatic switches, and operating electromagnets. (5) Electromagnets for other purposes - such as electromagnetic chucks for electromagnetic machines and electromagnetic vibrators.

principle

When the solenoid is energized, a magnetic field such as a magnet bar can be generated. The circle in the figure is the cross section of the wire, the point represents the current exiting the screen, the fork represents the inflow screen; the elliptical circle with the arrow is the magnetic field line. When a direct current passes through a conductor, a magnetic field is generated, and when a conductor of a solenoid (Solenoid) is produced, a magnetic field similar to a rod magnet is generated. When a magnetic substance is added to the center of the solenoid, the magnetic substance is magnetized to enhance the magnetic field. In general, the strength of the magnetic field generated by the electromagnet is related to the size of the direct current, the number of coil turns, and the magnetically conductive material at the center. When designing the electromagnet, attention will be paid to the distribution of the coil and the selection of the iron-conducting substance, and the size of the direct current is used to control Magnetic field strength. However, the material of the coil has electrical resistance that limits the amount of magnetic field that the electromagnet can produce, but with the discovery and application of superconductors there will be opportunities to break through existing limitations.

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