Magnetic properties of magnets
Magnets are capable of generating a magnetic field that attracts ferromagnetic substances such as iron, nickel, cobalt and other metals. The midpoint of a bar magnet is suspended by a thin wire, and when it is at rest, each of its two ends will point to the south and north of the Earth; the end pointing north is called the north pole or N pole, and the end pointing south is the south pole or S pole. If you think of the Earth as a large magnet, the Earth's geomagnetic north pole is currently the south pole and the geomagnetic south pole is the north pole. Between magnets and magnets, the same poles repel and opposite poles attract. Therefore, the compass and the South Pole repel, the North Pointer and the North Pole repel, while the compass and the North Pointer attract.
Classification of magnets
Magnets can be categorized as "permanent" and "non-permanent". Permanent magnets can be natural products, also known as natural magnets, or man-made (the strongest magnets are neodymium-iron-boron (NdFeB) magnets). [1] Non-permanent magnets, such as electromagnets, become magnetic only under certain conditions.
Magnets were not invented by man, they are naturally occurring magnetite. The ancient Greeks and Chinese discovered a naturally magnetized stone in nature and called it "magnetite". This stone could magically pick up small pieces of iron and always point in the same direction when swung at random. Early mariners used this magnet as their earliest compass to find their way at sea. The earliest discovery and use of magnets should be the Chinese, also known as the "compass", is one of the four great inventions of China.
After thousands of years of development, magnets have become a powerful material in our lives. By synthesizing alloys of different materials, it is possible to achieve the same effect as the magnet, but also to increase the magnetic force. Man-made magnets appeared in the 18th century, but the process of making stronger magnetic materials was slow until the 1920s when Alnico (aluminum nickel cobalt) was made. This was followed by ferrite in the 1950s and rare earth magnets [Rare Earth mag including NdFeB and SmCo] in the 1970s. Since then, magnetic science and technology has developed rapidly, and strong magnetic materials have made components more miniaturized.
2. Knowledge about magnets
The ancient Greeks and Chinese discovered that there is a naturally magnetized stone in nature, which they called "iron absorbing stone". This stone could magically pick up small pieces of iron and always point in the same direction when swung at random. Early mariners used this magnet as their earliest compass to find their way at sea.
After thousands of years of development, today magnets have become a powerful material in our lives. By synthesizing alloys of different materials can achieve the same effect as an iron absorber, but also increase the magnetic force. Man-made magnets appeared in the 18th century, but the process of making stronger magnetic materials was slow until the 1920s when Alnico (aluminum nickel cobalt) was made. This was followed by ferrite in the 1950s and rare earth magnets [Rare Earth mag including NdFeB and SmCo] in the 1970s. Since then, magnetic science and technology has developed rapidly, and strong magnetic materials have made components more miniaturized.
3. Information about magnets
The components of magnets are iron, cobalt, nickel, etc. The atomic structure is special, the atoms themselves have a magnetic moment, and the general molecular arrangement of these minerals is chaotic.
The magnetic field affects each other and does not show the magnetism, but in the external forces (such as magnetic field) guide the molecular arrangement of the direction tends to converge, it shows the magnetism, which is commonly known as the magnet. Iron, cobalt, nickel, is the most commonly used magnetic substances, basically the magnet is divided into permanent magnets and soft iron, permanent magnets are coupled with strong magnetism, so that the spin of the magnetic material and the electron angular momentum so that the spin of the magnetic material and the electron angular momentum into a fixed direction of the arrangement of the soft magnet is coupled with the electric current (is also a method of adding magnetism) and so the current is removed from the soft iron will slowly lose its magnetism.
The magnet was not invented by man, there is natural magnetite, the first to discover and use the magnet should be the Chinese. That's why the compass is one of the four great inventions of the Chinese.
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 have been categorized as "permanent magnets" and "non-permanent magnets.
Permanent magnets can be natural products, also known as natural magnets, or artificially created (the strongest magnets are neodymium-iron-boron magnets). Non-permanent magnets heated to a certain temperature will suddenly lose magnetism, which is due to the composition of the magnet of the many "metamagnet" of the arrangement of the order from the disorder caused by the loss of magnetism into the magnetic field, when the magnetization strength reaches a certain value, it is magnetized, "metamagnet" of the arrangement from the disorder again. The arrangement of the "metamagnets" is again from disorder to order.
Basic knowledge: The ancient Greeks and the Chinese found a natural magnetized stone in nature, called "iron absorption stone". This stone could magically pick up small pieces of iron and always point in the same direction after swinging at random.
Early mariners used this magnet as their earliest compass to find their way at sea. Magnets have evolved over thousands of years, and today they are a powerful material in our lives.
By synthesizing alloys of different materials it is possible to achieve the same effect as a magnet, 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, in the 1950s, ferrite was produced, and in the 1970s, rare earth magnets [Rare Earth magnets include neodymium-iron-boron (NdFeB) and samarium cobalt (SmCo)] were produced. Since then, the technology of magnetism has developed rapidly, and the strong magnetic materials have made the components more miniaturized.
Editing magnetization (orientation) direction Most magnetic materials can be magnetized in the same direction until they are saturated, which is called the "magnetization direction" (orientation). 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 the "North Pole" of a magnet is that the North Pole of the magnet points to 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 can you tell the north pole of a magnet without labeling it? Obviously you can't tell by eye.
You can use a compass close to the magnet, and the needle pointing to the North Pole of the Earth will point to the South Pole of the magnet. How do I handle and store magnets safely? Always be very careful, as magnets can attract themselves together and may pinch your fingers.
Magnets can also damage themselves by bumping against each other (knocking off corners or cracking). Keep magnets away from magnetized objects such as floppy disks, credit cards, computer monitors, watches, cell phones, and medical equipment.
Keep magnets 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. How do I separate the magnets? Only materials that can be attached to the magnet can isolate it, and the thicker the material, the better the isolation.
What is the strongest magnet? The highest performance magnets are rare-earth magnets, and NdFeB is the most powerful of the rare-earth magnets. However, samarium cobalt is the most powerful magnet in environments above 200 degrees Celsius.
Edit this section of the types of magnets [Figure] magnets, should be called magnets, English Mag, magnets are now divided into two main categories, one is a soft magnet, one is a hard magnet; soft magnets, including silicon steel sheet and soft magnet core; hard magnets, including aluminum nickel cobalt, samarium cobalt, ferrite, and neodymium-iron-boron, which, the most expensive is samarium cobalt magnets, the most inexpensive is ferrite magnets, the highest performance of neodymium-iron-boron magnets, but the most stable and best temperature coefficient is aluminum nickel cobalt. The most stable and the best temperature coefficient is Alnico magnets, users can choose different hard magnetic products according to different needs.
4. Knowledge about magnets
Magnets are composed of iron, cobalt, nickel and other atoms, the internal structure of its atoms is relatively special, which itself has a magnetic moment. Magnets are capable of generating magnetic fields and have the property of attracting ferromagnetic substances such as iron, nickel, cobalt and other metals.
Types of magnets
1, shape class magnets. Square magnets, tile magnets, shaped magnets, cylindrical magnets, ring magnets, round sheet magnets, magnetic bar magnets, magnetic frame magnets.
2. Property class magnets. Samarium cobalt magnets, neodymium iron boron magnets (powerful magnets), ferrite magnets, alnico magnets, ferrochrome cobalt magnets.
3, industry magnets: magnetic components, motor magnets, rubber magnets, plastic magnets and other types.
4, the magnet is divided into permanent magnets and soft magnets, permanent magnets are coupled with strong magnetism, so that the spin of the magnetic material and the electron angular momentum into a fixed direction of the arrangement of soft magnets is coupled with electricity.
Expanded information:
The discovery of magnets.
Magnets are naturally occurring magnetite. The ancient Greeks and Chinese discovered a naturally magnetized stone in nature and called it "magnetite". This stone could magically pick up small pieces of iron and always point in the same direction after swinging at random.
Early mariners used this magnet as their earliest compass to find their way at sea. It was the Chinese who first discovered and used magnets to make the "compass", one of the four great inventions of China.
After thousands of years of development, magnets have become a powerful material in our lives. By synthesizing alloys of different materials, it is possible to achieve the same effect as a magnet, 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.
Baidu Encyclopedia-Magnets
5. What is the basic common sense and application of NdFeB magnets
NdFeB powerful magnets use instructions and precautions
1: NdFeB powerful magnets magnetism is very strong, the operation of the hand or the other parts of the body should be avoided to be caught by the magnets, for the size of the larger magnets should be more attention to the safety of the person and protection.
2: Do not bring the magnet close to electronic medical devices or people carrying medical devices such as pacemakers.
3: Do not swallow the magnet. In case of accidental swallowing, please go to the hospital immediately for treatment. Do not keep the magnet within the reach of children.
Note:
In order not to be safe and not to affect the use of the magnet, please be sure to comply with the following rules:
4: The magnet should be used to ensure that the workplace is clean, so as not to adsorb iron filings and other fine impurities on the surface of the magnet to affect the normal use of the product.
5: NdFeB powerful magnet is very strong magnetic, such as its strong impact, the magnet will be broken and fly apart, magnetic fragments may fly into the eyes, please be careful to use.
6: NdFeB magnets are suitable for storage in a ventilated and dry room, acidic, alkaline, organic solvents, water, high temperature and humid environment is easy to make the magnet rust, plating off the magnet powder demagnetization. For the unplated products should pay more attention to the storage can be appropriate oil rust, which is the main reason we recommend neodymium iron boron magnet surface anti-corrosion treatment.
7: After heating, the magnetic properties of NdFeB Power Magnets will be greatly reduced. Please refer to the catalog or relevant temperature characteristic pointers and be careful not to overheat when assembling or using the magnets.
6. About the magnet, please be more comprehensive I will look carefully
/view/38638 1. First of all, a metal wire with good conductivity, the length of the wire is related to the size of the magnet you want to make.
Then both ends of the wire are connected to the power supply, of course one to the positive and one to the negative, and then connected in parallel with a resistor, and it is an adjustable size of the resistor. This is common sense middle school physics (note the danger) 2. by magnetic field The magnetic field is a special kind of matter.
The magnetic field exists around the magnet, and the interaction between magnets is mediated by the magnetic field.3. The magnetism of the magnet is weakened by the effects of the external environment, such as changes in temperature, interference from other magnetic or electric fields.
Magnets of different materials fade to different degrees. The only way to make a faded magnet magnetic again is to magnetize it (i.e., remagnetize it).
Metal magnets (the so-called strong magnets) are more magnetic than ordinary ferrite magnets because the surface magnetic field is stronger after the metal magnet is magnetized. This is due to the physical properties of the different magnetic materials.
Magnetic poles do not change, but we can use the same technical means to fill the same magnet with many (even) poles, that is, a magnet can have a number of N poles and the corresponding S poles.4. Strictly speaking, the magnet, whether or not it is in contact with the magnet or the iron, the magnetic force will be naturally decayed over time.
If you exclude this factor, only consider the effect of the medium around it, analyzed the following cases: the magnet adsorbed iron and magnets and magnets in the case of mutual attraction combined together (the permeability of the medium is greater than the air permeability), not only will not accelerate the natural rate of decay of the magnet's magnetic force, on the contrary, it will slow down the rate of decay; if the magnet and the magnet in the repulsion of the case through the external force to make If the magnet and the magnet in the case of repulsion by external force to make them merge together (the permeability of the medium is less than the air permeability, that is, anti-magnetic medium), it will accelerate the decay rate of its magnetic force. Magnets in the case of high temperature or violent impact, the magnetic force will quickly disappear.
5. You can use a very strong magnetic rare earth permanent magnets, ordinary magnets "magnetization", that is, sucking ordinary magnets; you can also use a coil set in ordinary magnets, with a high current on the coil discharge method, magnetization (usually with a large capacitor charging a few hundred volts after the discharge of the coil). Magnetization should pay attention to the direction of the current, so that the magnetic field generated by the coil and the magnetic field of the magnet.
6. The same principle as above 7. Iron absorption generally refers to magnetite (containing iron tetraoxide) or its powder pressed into shape permanent magnets, black. Can no longer oxidize and rust.
And other magnets (the primary component is iron), is made of magnetized metallic iron or steel, it is the same as other iron and steel, can be oxidized rust, oxidized sector magnetic fade away. (The primary component of the magnet is iron tetraoxide, 3-valent iron ions) 8. Maglev train is a high-tech transportation using magnetic poles of attraction and repulsion.
Simply put, the repulsive force makes the train hang up, attraction makes the train start. Maglev trains are equipped with electromagnets, and coils are installed at the bottom of the railroad.
When energized, the polarity of the magnetic field generated by the ground coil is always the same as the polarity of the electromagnet on the train, and the two are "equally repulsive", so the repulsive force makes the train levitate. Both sides of the tracks are also equipped with coils, alternating current makes the coil into an electromagnetic body.
It interacts with the electromagnet on the train to move the train forward. Train head of the electromagnetic body (N pole) by the track a little ahead of the electromagnetic body (S pole) attracted, at the same time by the track a little behind the electromagnetic body (N pole) to repel - the result is a "push" a "pull! ".
The Maglev train runs with a certain gap (generally 1-10cm) to the track, so it runs safely, smoothly and comfortably, without noise, and can realize fully automated operation. The service life of a Maglev train can be up to 35 years, while that of an ordinary wheeled train is only 20-25 years.
The lifespan of a Maglev train track is 80 years, while an ordinary track is only 60 years. In addition, the maximum speed of a Maglev train is reached within 39 seconds after startup, and the current maximum speed is 552 kilometers per hour.
According to German scientists predicted that by 2014, the maglev train will reach a speed of 1,000 kilometers per hour with the new technology. And the maximum speed of a typical wheeled train is 300 kilometers per hour.
The maglev train utilizes the principle of "same sex repulsion, opposite sex attraction", so that the magnet has the ability to resist gravity, so that the car body completely off the track, suspended from the track at a distance of about 1 centimeter, traveling in the air, creating a near "zero height" The miracle of space flight. The world's first maglev train demonstration line - Shanghai maglev train, after the completion of the Pudong Longyang Road station to the Pudong International Airport, more than 30 kilometers in just 6 ~ 7 minutes.
The Shanghai Maglev train is a "normal-conducting magnetic absorption type" (referred to as "normal-conducting") Maglev train. Is the use of "opposites attract" principle design, is a suction levitation system, the use of installation in the train on both sides of the bogie on the levitation electromagnet, and laying on the track of the magnets, under the action of the magnetic field generated by the suction is the vehicle floating up.
The bottom of the train and both sides of the top of the bogie installation of electromagnets, in the "I" above the rail and the upper arm part of the lower part of the reaction plate and inductive steel plate, respectively, control the electromagnet current so that the electromagnet and the track to maintain a 1-centimeter gap, so that the bogie and the train attraction between the train and the train gravity to balance each other, the use of magnet attraction to float the train up 1 centimeter. Magnet attraction will float the train about 1 cm, so that the train suspended on the track operation. This must precisely control the current of the electromagnet.
The drive of a levitated train is exactly the same as the principle of a synchronous linear motor. In layman's terms, the alternating current flowing in the coils located on both sides of the track turns the coils into electromagnets, which, due to their interaction with the electromagnets on the train, start the train.
The N pole of the electromagnet at the head of the train is attracted by the S pole of the electromagnet mounted on the track a little bit in front of it, and at the same time it is repelled by the N pole of the electromagnet mounted a little bit behind it on the track. When the train moves forward, the current flowing in the coil is reversed, that is, the original S pole into N pole, N pole into S pole.
The cycle alternates, and the train moves forward. Stability is controlled by the guidance system.
"Normal guidance type magnetic suction" guidance system, is installed in the train side of a group of electromagnets dedicated to guidance. When the train is shifted from side to side, the guiding electromagnet on the train interacts with the side of the guiding rail, generating repulsive force and restoring the vehicle to its normal position.
If the train is running on a curve or ramp, the control system controls the current in the guiding magnets to control the operation. The idea of the "normally guided" maglev train was proposed by the German engineer Hermann Kemper in 1922.
7. Small inventions related to magnets
A sewing needle, magnetize it with a magnet, and then tie it to the middle part of the needle with a cotton thread, hang it on a bracket, and it will become a compass. Make a floating compass:
Take a magnetized steel needle, thread it horizontally through a small piece of cork, and place it in a ceramic bowl of water.
We can also make a more elaborate box compass:
Find a small round cardboard or plastic box (not steel). Cut a piece of cardboard the same size as the box, stick a piece of white paper on it, mark S, N and so on, put a plastic nail from the back on the round piece of paper, put the round piece of paper into the box, the center of the box has an upright upward needle column. Then find a waste shaving blade, cut into a narrow diamond shape, with a nail in the center of a small pit, placed on the tip of the pin to try, if you can not balance, use scissors to repair until it can be balanced. Put it on a strong magnet to magnetize it, and set it up on the pin post inside the box. Cover the mouth of the box with a layer of transparent cellophane (with glass is better), the original lid open a large hole and then cover it, it is a box compass.
A freely rotating magnet always points in a north-south direction when it is at rest. When people learned about this property of magnets, they used it to make a compass, a tool for indicating direction.
Why does a magnetic needle always point north and south when it is at rest? Because the Earth is a large magnet, its two magnetic poles close to the poles of the Earth, under the action of geomagnetic force, the magnetic needle is sucked to the north-south direction. We know that the magnetic poles of different names are attracted to each other, and the S pole of geomagnetism is at the north end and the N pole is at the south end, so the N pole of the magnetic needle always points to the north, and the S pole always points to the south. The magnetic needle's pole and the Earth's magnetic pole are not in contact, but they can attract each other, which indicates that there is an invisible thing around the magnet, people call it "magnetic field". The existence of the Earth's magnetic field is the reason why the magnetic needle can indicate north and south.
The world's earliest compass, to be counted in our country during the Warring States period manufactured "Sinan". It is a natural magnet faceted into the shape of a spoon, the spoon handle is the S pole, so that the center of gravity falls in the middle of the round and smooth head of the spoon, and then put the spoon on a smooth plate. To use it, the head of the spoon is flattened and its handle is pivoted by hand to make it turn. When the Sinan stopped, its long handle pointed south. In those days, when some people went to the mountains to collect jade, they were afraid of losing their way, so they took Sinan with them to identify the direction.
After the invention of Sinan, people continued to study and improve the tools of guidance. In the early years of the Northern Song Dynasty, a guide fish was made. It is made of a thin piece of steel, shaped like a fish. Fish belly concave down some, like a boat, can float on the water. After magnetizing it, put it into a porcelain bowl of water, you can indicate the direction. Because the friction of water is smaller than solid, guide fish turn up more flexible, so it is more flexible than Sinan more accurate.
At that time, there was also a guide fish made of wood, that is, with a piece of wood carved into a fish, like a finger so big. From the mouth of the fish to dig a hole, inside the bar magnet, so that its S pole towards the head of the fish, and seal the mouth with wax. Also use a needle to insert into the mouth of the fish, the guide fish is ready. Put it on the surface of the water, the small needle in the mouth of the fish points to the south.
China is not only the first country in the world to invent the compass, but also the first country to use the compass in navigation. According to records, in the Southern Song Dynasty, the seafarers already used the "compass" to indicate the direction. This is the combination of compass and compass guide tool. Compass disk made of wood, there are also made of copper, the disk is engraved around the southeast, northwest and other directions, the disk in the center of a compass. As long as the compass pointed in the direction, and the disk on the south orientation alignment, you can easily identify the direction of navigation.
The compass is also used in the military, when marching and fighting, if you encounter cloudy days and dark nights, you can use the compass to identify the direction.
The compass was also used in the military.