A magnet is an object or material that produces a magnetic field, usually made of a metal alloy, and has strong magnetic properties. Traditionally, they can be divided into "permanent magnets" and "non-permanent magnets".
Permanent magnets can be natural products, also known as natural magnets, or they can be man-made (the strongest magnets are neodymium magnets).
Non-permanent magnets, sometimes lose their magnetic properties.
The ancient Greeks and Chinese discovered a naturally magnetized stone in nature and called it "iron absorption stone". The stone could magically pick up small pieces of iron and always point in the same direction when swung around. Early mariners used this magnet as their first compass to find their way around the sea.
The magnet was also used as a compass to find their way around the sea.
After thousands of years of development, today magnets have become powerful materials in our lives. By synthesizing alloys of different materials it is possible to achieve the same effect as an iron absorber, but also to increase the magnetic force. Man-made magnets appeared in the 18th century, but the process of creating stronger magnetic materials was slow until the 1920s, when aluminum-nickel-cobalt (Alnico) was created. Subsequently, the 1950s produced a ferrite (Ferrite), the 1970s produced rare earth magnets [Rare Earth magnet including neodymium iron boron (NdFeB) and samarium cobalt (SmCo)].
Since then, the technology of magnets has advanced dramatically, and strong magnetic materials have allowed for more miniaturization of components.
Most magnetic materials can be magnetized to saturation in the same direction, which is called the "direction of magnetization" (orientation). Magnets without orientation (also called isotropic magnets) are much less magnetic than oriented magnets (also called anisotropic magnets).
What is the standard industrial definition of "north and south poles"?
The definition of "North Pole" is that the North Pole of a magnet is pointing towards the North Pole of the Earth when the magnet is rotated randomly. Similarly, the south pole of a magnet points to the south pole of the earth.
How do you identify the north pole of a magnet without labeling it?
Obviously you can't tell by eye alone. You can use a compass close to the magnet, and the needle pointing to the Earth's North Pole will point to the magnet's South Pole.
How do I handle and store a magnet safely?
Always be very careful, as magnets can attract themselves together and can pinch your fingers. It is also possible to damage the magnets themselves by bumping them against each other (knocking off edges or cracking them).
Keep magnets away from magnetized objects such as floppy disks, credit cards, computer monitors, watches, cell phones, and medical equipment.
Magnets should be kept away from pacemakers.
Larger magnets should have plastic or cardboard spacers between each piece to ensure that the magnets can be easily separated.
Magnets should be stored in a dry, temperature-controlled environment whenever possible.
How can I isolate my magnets?
Only materials that can be adsorbed onto the magnet can act as a magnetic field barrier, and the thicker the material, the more effective the barrier.
What is the strongest magnet?
The highest performance magnets are rare earth magnets, and among the rare earth magnets NdFeB is the most powerful magnet. However, samarium cobalt is the most powerful magnet in environments above 200 degrees Celsius.
Magnets, should be called magnets, English Magnet, magnets are now divided into two main categories, one is a soft magnet, a class of hard magnets;
Soft magnets, including silicon steel sheet and soft magnet core; hard magnets, including alnico, samarium cobalt, ferrite and neodymium iron boron, which, the most expensive samarium cobalt magnets, the most inexpensive ferrite magnets, the highest performance of neodymium iron boron magnets, but the most stable performance!
Cobalt magnets are the best temperature coefficient, users can choose different hard magnetic products according to different needs.
What defines the performance of a magnet?
There are 3 main performance parameters to define the performance of a magnet:
Remaining Br :After the permanent magnet is magnetized to technical saturation and the external magnetic field is removed, the Br retained is called the residual magnetic induction strength.
Coercivity Hc :The reverse magnetic field strength that needs to be added to reduce the B of a permanent magnet magnet magnetized to technical saturation to zero is known as the magnetic susceptibility coercivity, which is simply
known as the coercivity
Magnetic energy product BH :It represents the density of the magnetic energy that is built up by the magnet in the space of the air-gap (the space of the magnet's two poles), i.e., the static magnetic energy per unit volume of the air-gap. Since this energy is equal to the product of the magnet's Bm and Hm, it is called the magnetic energy product.
Magnetic field:The space that exerts a magnetic effect on the poles is the magnetic field
Surface magnetic field:The magnetic induction intensity at a specified location on the surface of a permanent magnet
How to choose a magnet?
Before deciding which magnet to choose, it should be clear what kind of function the magnet needs to perform?
The main function: to move an object, to fix an object or to lift an object.
Shape of magnet needed: circular, toroidal, square, tile or special shape.
Dimensions of the magnet required: length, width, height, diameter and tolerance, etc.
The suction power of the magnet required, the desired price and quantity, etc.
The compass was invented based on the nature of magnets
1 Points north and south
2 Attracts light objects
3 Electromagnets can be used to make electromagnetic relays
4. Electric motors
5 Generators
Our ancestors in the pre-Qin era had already accumulated a lot of knowledge in this area, and they often encountered magnetite, which is magnetite (the main type of magnet), in the prospecting of iron ore. magnetite, or magnetite (whose main component is iron tetraoxide). These discoveries were documented very early. The first record of these discoveries is found in several passages of the Guanzi: "
He who has magnetite on a mountain has gold and copper underneath."
Similar accounts are found in other ancient texts such as the Classic of Mountains and Seas. The magnet's iron absorbing properties were discovered very early, "Lv's Spring and Autumn Annals" nine volumes of proficient chapter has: "Ci recruited iron, or attracted also." At that time, the people called "magnet" for "Ci", and they regarded the magnet attracting iron as a mother's attraction to her children
. And think: "Stone is the mother of iron, but the stone has two kinds of charity and not charity, charity stone can attract his children, not charity stone can not attract." Before the Han Dynasty, people wrote about magnets as "ci shi", which means "loving stone".
Since magnets can attract iron, can they also attract other metals? Our ancestors made many attempts and found that magnets could not attract not only metals such as gold, silver and copper, but also objects such as bricks and tiles. In the Western Han Dynasty, people already realized that magnets can only attract
iron, but not other items. When two magnets are put together near each other, sometimes they attract each other, sometimes they repel each other. It is now known that magnets have two poles, one called the N pole and one called the S pole. The same poles repel each other and the opposite poles attract each other.
People did not know this at the time, but they were able to perceive the phenomenon.
To the Western Han Dynasty, there is a name of Luan Da's Fangshi, he used this nature of the magnet to do two chess-like things, by adjusting the polarity of the two pieces of the mutual position, sometimes the two pieces of the mutual attraction, and sometimes mutual repulsion. Luan Da called it "fighting chess". He offered this new
strange thing to Emperor Wu of Han Dynasty, and demonstrated on the spot. Han Wu Di was surprised, the dragon heart pleased, and even appointed Luan Da as "General Wuli". Luan Da utilized the nature of magnets to produce novelties to deceive Han Wu Di.
The Earth is also a large magnet, its two poles are in close proximity to the geographic South Pole and the geographic North Pole. Therefore the magnets on the surface of the Earth, which can freely rotate
when moving, it will be due to the nature of the magnets of the same sex repel each other, the opposites attract each other to indicate the north and south. The ancients didn't understand this enough, but they were very clear about this kind of phenomenon.
"Applications in traditional industry":
We have already mentioned some of the practical applications of magnetic materials when we talked about their sources of magnetism, electromagnetic induction, and magnetic "devices". In fact, magnetic materials have been used in various aspects of conventional industry.
For example, without magnetic materials, electrification would be impossible, because generators are used for power generation, transformers for power transmission, electric motors for electrical machinery, and loudspeakers for telephones, radios, and televisions. Numerous instruments and meters are used to magnet coils
structure. All of this has already been covered in the rest of the story.
"Magnetic Applications in Biology and Medicine":
Pigeon fanciers know that pigeons return to their nests automatically if they are released hundreds of kilometers away. Why do pigeons have such good home-recognition skills? It turns out that pigeons are very 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 tied to the pigeon's head, the pigeon will be lost. If pigeons fly over radio towers, powerful electromagnetic interference can also disorient them.
In medicine, the use of nuclear magnetic **** vibration can diagnose abnormal tissues in the human body, to determine the disease, which is more familiar with the nuclear magnetic **** vibration imaging technology, the basic principle is as follows: the atomic nucleus is positively charged and undergoes spin motion. Normally, the arrangement of the spin axis of the nucleus is
irregular, but when placed in an applied magnetic field, the nuclear spin space orientation from disorder to order transition. The magnetization vector of the spin system grows gradually from zero, and when the system reaches equilibrium, the magnetization strength reaches a stable value. If the nuclear spin system is subjected to external effects, such as a certain frequency of radio frequency excitation of the nucleus can cause *** vibration effect. After the cessation of the radio frequency pulse, the spin system has been excited nuclei, can not maintain this state, will return to the magnetic field in the original arrangement of the state, while releasing a weak energy, become radio signals, this many
More than one signal detection, and make it when the spatial resolution, you get the distribution of the nuclei of the movement of the image. Nuclear magnetic **** vibration is characterized by the flow of liquid does not produce a signal called the flow effect or flow blanking effect. Therefore, blood vessels are grayish-white tubular structures, while the blood is black without signal.
This makes it easy for the blood vessels to be separated by soft tissue. The normal spinal cord is surrounded by cerebrospinal fluid, which is black, and has white dura mater lined with fat so that the spinal cord shows up as a white, strongly signaling structure. Nuclear magnetic **** vibration has been applied to diagnostic imaging of systems throughout the body.
The best results are the cranial brain, and its spinal cord, the heart, blood vessels, joints, bones, soft tissues and pelvic cavity. Cardiovascular disease can not only observe the anatomical changes of the chambers, large vessels and valves, but also ventricular analysis, qualitative and semi-quantitative diagnosis, can be made in multiple sections
map, high spatial resolution, showing the heart and lesions of the whole picture, and its relationship with the surrounding structures, is better than the other X-ray imaging, two-dimensional ultrasound, radionuclide and CT examination.
Magnetism is not only diagnostic, but can also help treat disease. Magnets are a medicinal herb used in ancient Chinese medicine. Nowadays, the magnetic difference between different components of blood is utilized to separate red and white blood cells. In addition, the interaction of the magnetic field and the human meridian can realize the magnetic therapy, in the treatment
The treatment of a variety of diseases has a unique role, there has been a magnetic therapy pillow, magnetic therapy belt and other applications. The iron remover made of magnets can remove iron powder that may exist in flour, etc., magnetized water can prevent boiler scaling, and magnetized seeds can increase crop yields to a certain extent.
"Magnetic Applications in Astronomy, Geology, Archaeology and Mining":
We already know that the earth is a huge magnet, so where does its magnetism come from? Has it been there since ancient times? How is it related to geological conditions? And what about magnetic fields in the universe?
At least in pictures we have all seen the brilliant Northern Lights. The Northern Lights have been recorded in our country since ancient times. The Northern Lights are actually the result of the interaction between particles in the solar wind and the geomagnetic field. The solar wind is a stream of high-energy charged particles emitted by the sun. When they reach the Earth,
and the geomagnetic field interaction, as if the current wire in the magnetic field force, making these particles to the north and south poles of the movement and aggregation, and and the Earth's high-altitude thin gas collision, the result of gas molecules by the excitation, and thus the light.
Sunspots are regions on the Sun where magnetic activity is very intense. Sunspot eruptions can have an impact on our lives, such as temporarily disrupting radio communications. Therefore, the study of sunspots is of great importance to us.
Changes in geomagnetism can be used to explore for mineral deposits. Since all materials have strong or weak magnetic properties, if they come together to form an ore deposit, they will inevitably interfere with the geomagnetic field of the neighboring area, causing anomalies in the geomagnetic field. According to this, the magnetic field of the earth can be measured on land, in the ocean, or in the air, and a geomagnetic map can be obtained, and the areas with abnormal magnetic fields on the geomagnetic map can be analyzed and further explored, and unknown mineral deposits or special geological formations can often be found.
Rocks of different geological ages often have different magnetic properties. Therefore, the magnetic properties of rocks can be used to assist in determining changes in geologic age and crustal shifts.
Many mineral resources are ****ogenic, meaning that several minerals are mixed together, and they have different magnetic properties. Using this feature, people developed a magnetic separator, the use of different components of the different magnetic properties of minerals and the difference in the strength of the magnetic properties, with a magnet to attract these substances
Substances, then they are subject to the attraction of the difference, as a result, can be mixed together with the different magnetic properties of the minerals to separate, to achieve the magnetic separation of minerals.
Magnetic applications in the military:
Magnetic materials are also widely used in the military. For example, ordinary mines or landmines can only explode on contact with the target, and are therefore of limited use. If magnetic sensors are installed on mines or mines, since tanks or warships are made of steel, the sensors can detect a change in the magnetic field when they are close to the target (without touching the target), causing the mines or mines to explode, thus increasing their lethality.
In modern warfare, air control is one of the keys to winning a battle. However, the airplane is easily detected by the enemy's radar in the process of flight, thus having a greater danger. In order to avoid enemy radar monitoring, the aircraft surface can be coated with a layer of special magnetic material -
Wave-absorbing material, which can absorb the electromagnetic waves emitted by the radar, making the radar electromagnetic waves rarely reflect, so the enemy radar can not detect the radar echo, can not be found on the aircraft, which makes the aircraft to achieve the purpose of stealth. This is the famous "stealth airplane".
The stealth technology is currently the world's military research in the field of a major hot spot. The U.S. F117 stealth fighter is an example of the successful use of stealth technology.
In the U.S. "Star Wars" program, there is a new type of weapon "electromagnetic weapons" development research. Traditional artillery utilizes the thrust generated by the instantaneous expansion of the ammunition when it explodes to rapidly accelerate the projectile and push it out of the cannon. Electromagnetic artillery is to put the shell in the solenoid,
To the solenoid energized, then the solenoid generated by the magnetic field of the shell will produce a huge impetus, the shell will be shot. This is the so-called electromagnetic cannon. Similarly, there are electromagnetic missiles and so on.
Edit | Back to top Knowledge There are many types of magnets. Generally divided into two categories: permanent magnets and soft magnets. By magnets, we generally mean permanent magnets.
Permanent magnets are divided into two categories:
The first category: metal alloy magnets, including neodymium-iron-boron magnets (Nd2Fe14B), samarium cobalt magnets (SmCo), aluminum-nickel-cobalt magnets (ALNiCO)
The second category: ferrite permanent magnet materials (Ferrite)
1, neodymium-iron-boron magnets: it is currently found to be the highest performance of commercialized magnets. It is the highest performance magnet, known as the king of magnets, has a very high magnetic properties of its maximum magnetic
energy product (BHmax) is higher than the ferrite (Ferrite) more than 10 times. Its mechanical properties are also very good. The maximum working temperature can
reach 200 degrees Celsius. And its texture is hard, stable performance, has a very good cost performance, so its application is extremely wide. But because of its chemical activity
Strong, so it must be its surface tinting treatment. (such as plating Zn, Ni, electrophoresis, passivation, etc.).
2. Ferrite magnets: its main raw materials include BaFe12O19 and SrFe12O19, made through the ceramic process, the texture is relatively hard, is a
brittle materials, due to the ferrite magnets have a very good temperature resistance, low price, moderate performance, has become the most widely used permanent magnets.
3. Alnico magnets: an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. The casting process can be processed to produce
different sizes and shapes, and the workability is very good. Cast Alnico magnets have the lowest reversible temperature coefficient and can operate at temperatures up to 600 degrees Celsius. Alnico permanent magnets are widely used in a variety of instrumentation and other applications.
4, samarium cobalt (SmCo) is divided into SmCo5 and Sm2Co17 according to the different composition, and its development is limited due to the expensive price of the material. Samarium
SmCo, as a rare earth permanent magnet, not only has a high magnetic energy product (14-28MGOe), reliable coercivity and good temperature
characteristics. Compared with NdFeB magnets, SmCo magnets are more suitable to work in high temperature environment.
With the development of society, the application of magnets is also more and more extensive, from high-tech products to the simplest packaging magnets, the most widely used
or neodymium iron boron magnets and ferrite magnets. From the history of the development of magnets, the late nineteenth century and early twentieth century, people mainly use carbon
steel, tungsten steel, chromium steel and cobalt steel for permanent magnetic materials. At the end of the 1930s, the successful development of alnico magnets, only to make the large-scale application of magnets
became possible. In the 1950s, barium ferrite magnets appeared, both to reduce the cost of permanent magnets, but also to broaden the scope of application of permanent magnet materials to
high-frequency field. To the sixties, the emergence of samarium cobalt permanent magnets, the application of magnets opened up a new era. 1967, the United States Dayton
University of Strnat, developed into samarium cobalt magnets, marking the arrival of the rare earth magnets. So far, rare-earth permanent magnets have experienced the first generation of
SmCo5, the second generation of precipitation-hardened Sm2Co17, the development of the third generation of Nd-Fe-B permanent magnet materials. At present, ferrite magnets are still the largest amount of
permanent magnet materials, but the output value of Nd-Fe-B magnets has greatly exceeded the ferrite permanent magnet materials, the production of Nd-Fe-B magnets has developed into a major industry
Magnetic force size is arranged as follows: Nd-Fe-B magnets, samarium cobalt magnets, alnico magnets, ferrite magnets.
Magnet production process: neodymium iron boron magnets, samarium cobalt magnets, aluminum nickel cobalt magnets, ferrite magnets production process is also different. In terms of process, there are sintered NdFeB magnets and bonded NdFeB magnets, we mainly talk about sintered NdFeB magnets.
Process: Ingredients → melting ingot → powder → pressing → sintering and tempering → magnetic detection → grinding → pinning and cutting
Working → electroplating → products. Among them, batching is the foundation, sintering and tempering is the key
NdFeB magnet production tools: smelting furnace, jaw machine, ball mill, air mill, press molding machine, vacuum sealing machine, isostatic pressure machine,
sintering furnace, heat treatment vacuum furnace, magnetic performance tester, gaussmeter.
NdFeB magnet processing tools: there are special slicing machine, wire cutting machine tools, flat grinding machine, double-sided machine, punching machine, chamfering machine, electroplating equipment.
Maglev train is a magnetic levitation high-speed train system that uses contactless electromagnetic levitation, guidance and drive system. Its speed can reach more than 500 kilometers per hour, is today the world's fastest ground passenger transportation, has the advantages of fast speed, strong climbing ability, low energy consumption when running noise
small, safe and comfortable, no fuel, less pollution and so on. And it adopts the use of elevated methods, taking up very little arable land. Maglev trains mean that these trains utilize the basic principles of magnetism to levitate on rails instead of the old steel wheel and rail trains. Maglev technology uses electromagnetic force to lift the entire train car, getting rid of the nasty friction and unpleasant clanking sound, and realizing fast "flight" without contact with the ground and without fuel.