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Application of magnetic phenomena

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. "Magnetic applications in the biological and medical world": Pigeon fans know that if they fly hundreds of kilometers away, they will automatically return home. Why do pigeons have such a good recognition skills? It turns out that pigeons are sensitive to the Earth's magnetic field and they can use their 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. 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. 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, geology, archaeology and mining": We already know that the earth is a huge magnet, so where does its magnetism come from? Has it been since ancient times? What is the connection between it and the 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.