Small knowledge of magnets

Magnetism of magnet

Magnets can generate magnetic fields and attract ferromagnetic substances, such as iron, nickel, cobalt and other metals. Hang the midpoint of the bar magnet with a thin wire. When it is at rest, its two ends will point to the south and north of the earth respectively. One end pointing to the north is called North Pole or N Pole, and the other end pointing to the south is called Guiding Pole or S Pole. If we imagine the earth as a big magnet, the geomagnetic north pole of the earth is the guiding pole at present, and the geomagnetic south pole refers to the north pole. Between magnets, the same sex repels and the opposite sex attracts. So the compass repels the south pole, the north arrow repels the north pole, and the compass attracts the north arrow.

Classification of magnets

Magnets can be divided into "permanent magnets" and "non-permanent magnets". Permanent magnets can be natural products, also known as natural magnets, or artificial (the strongest magnet is neodymium magnet). [1] Non-permanent magnets, such as electromagnets, are magnetic only under certain conditions.

Magnets are not invented by people, but natural magnetite. The ancient Greeks and China discovered that there was a naturally magnetized stone in nature, called a "magnet". This kind of stone can magically pick up a small piece of iron and swing it at will and always point in the same direction. Early navigators used this magnet as their earliest compass to tell directions at sea. China, the "compass", one of China's four great inventions, was the first to discover and use magnets.

After thousands of years of development, magnets have become a powerful material in our life today. By synthesizing alloys of different materials, we can achieve the same effect as magnets and improve the magnetic force. /kloc-artificial magnets appeared in the 0/8th century, but the process of making stronger magnetic materials was very slow, and Al-Ni-Co was not produced until the 1920s. Subsequently, ferrite was made in 1950s, and rare earth magnets (including NdFeB and SmCo) were made in 1970s. At this point, magnetic technology has developed rapidly, and ferromagnetic materials have also made components more miniaturized.

2. Knowledge about magnets

The ancient Greeks and China discovered that there was a naturally magnetized stone in nature, called a "magnet". This kind of stone can magically pick up a small piece of iron and swing it at will and always point in the same direction. Early navigators used this magnet as their earliest compass to tell directions at sea.

After thousands of years of development, magnets have become a powerful material in our life today. By synthesizing alloys of different materials, we can achieve the same effect as magnets and improve the magnetic force. /kloc-artificial magnets appeared in the 0/8th century, but the process of making stronger magnetic materials was very slow, and Al-Ni-Co was not produced until the 1920s. Subsequently, ferrite was made in 1950s, and rare earth magnets (including NdFeB and SmCo) were made in 1970s. At this point, magnetic technology has developed rapidly, and ferromagnetic materials have also made components more miniaturized.

3. Information about magnets

Magnets are composed of atoms with special structures such as iron, cobalt and nickel, and the atoms themselves have magnetic moments, so these mineral molecules are generally arranged in disorder.

When magnetic fields interact, they can't show magnetism, but under the guidance of external forces (such as magnetic fields), the molecular arrangement directions tend to be consistent, showing magnetism, which is also commonly known as magnets. Iron, cobalt and nickel are the most commonly used magnetic substances. Basically, magnets are divided into permanent magnets and soft iron. The permanent magnet and strong magnetism make the spin and angular momentum of the magnetic substance arranged in a fixed direction. Adding current to the soft magnet (also a method of adding magnetic force) to remove the soft iron will gradually lose its magnetism.

Magnets are not invented by humans, but there are natural magnetite. It should be China who first discovered and used magnets. Therefore, the compass is one of the four great inventions of China people.

Magnets refer to objects or materials that can generate magnetic fields. They are usually made of metal alloys and have strong magnetism. Traditionally it can be divided into "permanent magnets" and "non-permanent magnets".

Permanent magnets can be natural products, also known as natural magnets, or artificial (the strongest magnet is neodymium magnet). When a non-permanent magnet is heated to a certain temperature, it will suddenly lose its magnetism, which is caused by the arrangement of many "meta-magnets" that make up the magnet from order to disorder. Put the lost magnet into the magnetic field. When the magnetization reaches a certain value, it is magnetized again, and the arrangement of "super magnets" changes from disorder to order.

Basic knowledge: The ancient Greeks and China discovered that there is a naturally magnetized stone in nature, which is called a "magnet". This kind of stone can magically pick up a small piece of iron and swing it at will and always point in the same direction.

Early navigators used this magnet as their earliest compass to tell directions at sea. Magnets have developed for thousands of years, and today magnets have become a powerful material in our lives.

By synthesizing alloys of different materials, we can achieve the same effect as magnets and improve the magnetic force. /kloc-artificial magnets appeared in the 0/8th century, but the process of making stronger magnetic materials was very slow, and Al-Ni-Co was not produced until the 1920s.

Subsequently, ferrite was made in 1950s, and rare earth magnets (including NdFeB and SmCo) were made in 1970s. At this point, magnetic technology has developed rapidly, and ferromagnetic materials have also made components more miniaturized.

Edit the magnetization (orientation) direction of this paragraph. Most magnetic materials can be magnetized to saturation in the same direction, which is called "magnetization direction" (orientation direction). Most magnetic materials can be magnetized to saturation in the same direction, which is called "magnetization direction" (orientation direction).

Non-oriented magnets (also called isotropic magnets) are much weaker than oriented magnets (also called anisotropic magnets). What is the standard industrial definition of "North and South Pole"? [Figure] The definition of the "north pole" of a magnet is that after the magnet rotates at will, its north pole points to the north pole of the earth.

Similarly, the south pole of the magnet also points to the south pole of the earth. How can you tell the north pole of a magnet without labeling it? Obviously, eyes alone can't tell the difference.

You can use a compass to get close to the magnet, and the pointer pointing to the north pole of the earth will point to the south pole of the magnet. How to handle and store magnets safely? Be very careful, because magnets attract each other and may pinch your fingers.

When magnets attract each other, they may also be damaged by collision (knocking off corners or cracking). Keep the magnet away from easily magnetized objects, such as floppy disks, credit cards, computer monitors, watches, mobile phones, medical devices, etc.

Magnets should be kept away from pacemakers. For larger magnets, plastic or cardboard washers should be added between each magnet to ensure that the magnets can be easily separated.

Magnets should be stored in a dry and constant temperature environment as much as possible. How to achieve magnetic isolation? Only the material that can be adsorbed on the magnet can isolate the magnetic field, and the thicker the material, the better the magnetic isolation effect.

What is the strongest magnet? At present, the magnet with the highest performance is rare earth magnet, and NdFeB is the magnet with the strongest performance among rare earth magnets. But in the environment above 200 degrees Celsius, samarium and cobalt are the strongest magnets.

Edit the types of magnets in this paragraph [Figure] Magnets should be called magnetic steel, English Mag, and magnetic steel is now mainly divided into two types, one is soft magnetic and the other is hard magnetic; Soft magnetic includes silicon steel sheet and soft magnetic core; Hard magnets include Al-Ni-Co, Sm-Co, Ferrite and NdFeB, among which Sm-Co is the most expensive, Ferrite is the cheapest and NdFeB has the highest performance, but Al-Ni-Co has the most stable performance and the best temperature coefficient. Users can choose different hard magnetic products according to different needs.

4. Knowledge about magnets

Magnets are made up of atoms such as iron, cobalt and nickel. Their atoms have special internal structures and have their own magnetic moments. Magnets can generate magnetic fields and attract ferromagnetic substances, such as iron, nickel, cobalt and other metals.

Types of magnets

1, shape magnet. Square magnet, tile magnet, irregular magnet, cylindrical magnet, ring magnet, disc magnet, bar magnet, magnet frame magnet.

2. Attribute magnet. Sm-Co magnet, Nd magnet (strong magnet), ferrite magnet, Al-Ni-Co magnet, Fe-Cr-Co magnet.

3. Industry magnets: magnetic components, motor magnets, rubber magnets, plastic magnets, etc.

4. Magnets are divided into permanent magnets and soft magnets. Permanent magnets strengthen magnetism, so that the spin of magnetic substances and the angular momentum of electrons are arranged in a fixed direction, while soft magnets are electrified.

Extended data:

The discovery of magnets.

Magnets are natural magnetite. The ancient Greeks and China discovered that there was a naturally magnetized stone in nature, called a "magnet". This kind of stone can magically pick up a small piece of iron and swing it at will and always point in the same direction.

Early navigators used this magnet as their earliest compass to tell directions at sea. China was the first to discover and use magnets, that is, making a compass with magnets is one of the four great inventions in China.

After thousands of years of development, magnets have become a powerful material in our life today. By synthesizing alloys of different materials, we can achieve the same effect as magnets and improve the magnetic force. /kloc-artificial magnets appeared in the 0/8th century, but the process of making stronger magnetic materials was very slow, and Al-Ni-Co was not produced until the 1920s.

Baidu encyclopedia-magnet

5. What is the basic knowledge and application scope of neodymium magnet?

Instructions and precautions for use of NdFeB strong magnets

1: NdFeB strong magnets are very magnetic, so it is necessary to prevent hands or other parts of the body from being caught by magnets during operation, and pay more attention to personal safety and protection for larger magnets.

2. Never place the magnet near electronic medical equipment or people carrying pacemakers and other medical equipment.

3: Never swallow a magnet. If swallowed by mistake, please go to the hospital for treatment immediately. Please don't put the magnet out of children's reach.

note:

In order to be unsafe and not affect the use of magnets, please observe the following rules:

4. Magnets should be used in clean workplaces to prevent tiny impurities such as iron filings from being adsorbed on the surface of magnets, which will affect the normal use of products.

5: NdFeB strong magnet is very magnetic. If subjected to a strong impact, the magnet will break and fly away, and magnetic fragments may fly into the eyes. Please use it carefully.

6. NdFeB strong magnets are suitable for storage in ventilated and dry rooms. Acidic, alkaline, organic solvent, water, high temperature and humid environment are all easy to cause the magnet to rust, the coating to fall off, and the magnet to powder and demagnetize. More attention should be paid to the products without electroplating, which can be properly oiled and rusted when stored, which is also the main reason why we suggest that the surface of neodymium magnet should be treated with anti-corrosion.

7: After heating, the magnetism of NdFeB strong magnet will be greatly reduced. Please refer to the product catalog or the relevant temperature characteristic pointer, and be careful not to overheat when assembling or using magnets.

6. As for the magnet, please synthesize it, and I will look at it carefully.

/view/38638 1。 The first is a metal wire with good conductivity. The length of the metal wire is related to the size of the magnet you want to make.

Then both ends are connected to the power supply, of course, one is connected to the positive electrode and the other is connected to the negative electrode, and then a resistor is connected in parallel, and it is an adjustable resistor. This is junior high school physics common sense (pay attention to danger). 2. Magnetic field is a special substance.

There is a magnetic field around the magnets, and the interaction between magnets is mediated by the magnetic field. 3. The magnetism of the magnet will be weakened by the influence of external environment, such as temperature change, interference of other magnetic fields or electric fields, etc.

Magnets made of different materials have different degrees of fading. In order to make the decayed magnet magnetic again, only the method of magnetizing (that is, re-magnetizing the magnet) is adopted.

Metal magnets (so-called strong magnets) are more magnetic than ordinary ferrite magnets because the magnetized surface magnetic field of metal magnets is stronger. This is determined by the physical properties of different magnetic materials.

The magnetic poles will not change, but we can charge the same magnet with many (even more) poles through technical means, that is to say, a magnet can have several N poles and corresponding S poles. Strictly speaking, whether a magnet is in contact with a magnet or iron, the magnetic force will naturally decay with time.

If we exclude this factor and only consider the influence of the surrounding medium, we can analyze the following situations: magnets attract iron, and magnets combine with each other under the condition of mutual attraction (the permeability of the medium is greater than that of air), which will not accelerate the natural decay rate of magnet magnetic force, but will slow down the decay rate; If in the case of repulsion (the permeability of the medium is less than that of air, that is, diamagnetic medium), the magnet and magnet will be combined by external force, and the attenuation speed of their magnetic force will be accelerated. When the magnet encounters high temperature or violent impact, the magnetic force will disappear quickly.

5. Strong magnetic rare earth permanent magnets can be used to "magnetize" ordinary magnets, that is, attract ordinary magnets; You can also magnetize a magnet by winding a coil around an ordinary magnet and discharging the coil with a large current (usually charging the coil with a large capacitor of several hundred volts). Pay attention to the direction of current when magnetizing, so that the magnetic field generated by the coil is consistent with that of the magnet.

6. The same principle as 7 above. Magnetite generally refers to magnetite (containing ferroferric oxide) or a permanent magnet formed by pressing its powder, black. No longer oxidizes and rusts.

Other magnets (mainly iron) are made of magnetized metallic iron or steel. Like other steel, it can be oxidized and rusted, and the magnetism of the oxidized part disappears. (The main component of magnet is Fe3O4, ferric ion) 8. Maglev train is a high-tech means of transportation that uses the attraction and repulsion of magnetic poles.

Simply put, repulsion makes the train suspended, and gravity makes the train move. The maglev train is equipped with electromagnets and the bottom of the railway is equipped with coils.

After electrification, the polarity of the magnetic field generated by the ground coil is always the same as that of the electromagnet on the train, and they are "like poles repel each other", which makes the train suspend. Coils are also installed on both sides of the rail, and alternating current turns the coils into electromagnets.

It interacts with the electromagnet on the train to make the train move forward. The electromagnet (N pole) at the head of the train is attracted by the electromagnet (S pole) at the front of the track and repelled by the electromagnet (N pole) at the back of the track-the result is a "push" and a "pull".

The maglev train keeps a certain gap (generally1-10 cm) with the track during operation, so it runs safely, smoothly and comfortably, without noise, and can realize full-automatic operation. The service life of maglev train can reach 35 years, while that of ordinary wheel-rail train is only 20-25 years.

The service life of maglev train track is 80 years, while that of ordinary track is only 60 years. In addition, the maglev train reached its maximum speed within 39 seconds after its start, and the current maximum speed is 552 kilometers per hour.

According to the prediction of German scientists, by 20 14 years, the speed of maglev train will reach 1000 km/h after adopting new technology. The maximum speed of ordinary wheel-rail trains is 300 kilometers per hour.

Based on the principle of "like-sex repulsion and opposite-sex attraction", the maglev train makes the magnet have the ability of defying gravity, which makes the car body completely off the track, suspended at a distance of about 1 cm from the track, and flew in the air, creating a miracle of space flight with almost zero height. Shanghai maglev train is the first demonstration operation line of maglev train in the world. After completion, it only takes 6-7 minutes from Longyang Road Station in Pudong to Pudong International Airport.

Shanghai maglev train is a kind of "constant magnetic attraction type" (referred to as "constant conductivity type"), which is designed according to the principle of "opposites attract" and is a suction suspension system. The suspension electromagnets installed on the bogies on both sides of the train and the magnets laid on the track are used, and the vehicle is suspended by the suction generated by the magnetic field.

Electromagnets are installed at the bottom of the train and at the top of bogies on both sides. The induction plate and the induction steel plate are respectively installed above the I-beam track and below the upper arm. Control the current of electromagnet to keep a gap of 65,438 0 cm between electromagnet and track, and balance the attraction between bogie and train with the gravity of train. By the attraction of magnets, the train can float about 65,438+0 cm, and the train can be suspended on the rails. This must accurately control the current of the electromagnet.

The driving principle of suspension train is exactly the same as that of synchronous linear motor. Generally speaking, the alternating current flowing in the coils on both sides of the track can turn the coils into electromagnets, and the train will start because of the interaction with the electromagnets on the train.

The N pole of the electromagnet at the head of the train is attracted by the S pole of the electromagnet installed on the front track and repelled by the N pole of the electromagnet installed on the back track. When the train moves forward, the current in the coil flows in the opposite direction, that is, the original S pole becomes the N pole, and the N pole becomes the S pole.

When the cycles alternate, the train will run forward. Stability is controlled by the navigation system.

The "constant magnetic attraction" guiding system is a group of electromagnets installed on the side of the train for guiding. When the train deviates from the left and right, the guide electromagnet on the train interacts with the side of the guide rail to produce repulsive force, which makes the vehicle return to the normal position.

When the train runs on a curve or ramp, the control system can control the operation by controlling the current in the guide magnet. The idea of "normally oriented" maglev train was put forward by German engineer Herman Corpster in 1922.

7. Gadgets related to magnets

The sewing needle is magnetized with a magnet, then tied in the middle of the needle with cotton thread and hung on the bracket, which becomes a compass. Make another floating compass:

Take a magnetized steel needle, put it through a small cork and put it in a ceramic bowl filled with water, which is a floating compass.

We can also make a more exquisite box compass:

Find a small round paper box or plastic box (iron boxes are not allowed). Cut out a disk the size of a small box with cardboard, and paste a piece of white paper with the words S, N, etc. Press a plastic thumbtack on the round paper from the back and put the round paper in the box. There will be an upright pin in the center of the box. Find another scrapped shaving blade, cut it into a long and narrow diamond shape, make a small hole in the center with a nail, and try it on the needle tip. If it can't be balanced, use scissors to repair it until it can be balanced. Magnetize it with a strong magnet and put it on a pin in the box. Cover the box mouth with a layer of transparent cellophane (glass is better), and open a big hole in the original box cover and then cover it, which is a box compass.

A freely rotating magnet always points in the north-south direction at rest. When people know this characteristic of magnet, they use it to make a compass, a tool to indicate the direction.

Why does the needle always point north and south when it is stationary? Because the earth is a big magnet, its two poles are close to the two poles of the earth. Under the action of geomagnetic force, the magnetic needle is attracted to the north-south direction. We know that magnetic poles with different names attract each other. The S pole of geomagnetism is at the northern end and the N pole is at the southern end. Therefore, the N pole of the magnetic needle always points to the north and the S pole always points to the south. The magnetic pole of the magnetic needle is not in contact with the magnetic pole of the earth, but they can attract each other, indicating that there is something invisible around the magnet, which is called "magnetic field". The existence of the earth's magnetic field is the reason why the magnetic needle can indicate the north and south.

The earliest compass in the world was "Sina" made in China during the Warring States Period. It grinds the natural magnet into the shape of a spoon, and the handle of the spoon is S pole, so that the center of gravity falls on the center of the round and smooth spoon head, and then the spoon is placed on a smooth plate. When in use, put the spoon head flat and move the spoon handle by hand to make it rotate. When Sina stopped, its long handle pointed south. At that time, someone went up the mountain to collect jade, afraid of getting lost, so they took Sina to find their way.

Since the invention of Sina, people have been studying and improving tour guide tools. In the early years of the Northern Song Dynasty, a kind of guide fish was created. It is made of a thin steel plate and looks like a fish. Fish's stomach is concave and can float on the water like a boat. After magnetization, put it in a porcelain bowl filled with water to indicate the direction. Because the friction of water is smaller than that of solids, small fish can rotate more flexibly, so it is more flexible and accurate than Sina.

At that time, there was a kind of guide fish made of wood, which was carved into a fish with a piece of wood as big as a finger. Dig a hole from the fish mouth, put a bar magnet in it, make its S pole face the fish head, and seal the mouth with wax. In addition, insert a needle into the fish's mouth and guide the blind fish. Put it on the water, and the small needle in the fish's mouth points south.

China is not only the first country in the world to invent the compass, but also the first country to use it in navigation. According to records, in the Southern Song Dynasty, navigators had used "compasses" to indicate their directions. This is a guide tool that combines a compass and a compass. The disc of a compass is made of wood and copper. The periphery of the disc is engraved with directions such as southeast and northwest, and a compass is placed in the center of the disc. As long as the direction pointed by the compass is aligned with the due south direction on the disk surface, the sailing direction can be easily identified.

Compasses are also used in the military. When marching in battle, if it is cloudy and dark, use them to identify the direction.