In 1822, the French physicists Arago and Lusak discovered that when current passes through a winding in which iron is present, it can magnetize the iron in the winding.
This is actually the initial discovery of the electromagnet principle. In 1823, Sterkin did a similar experiment: he wound 18 rounds of copper bare wires on a U-shaped iron bar that was not a magnet, and wound around U when the copper wire was connected to a voltaic battery. The copper coil on the iron rod generates a dense magnetic field, which makes the U-shaped iron rod an “electromagnet”. The magnetic energy of this kind of electromagnet is multiplied more than that of the permanent magnet. It can take up 20 times more weight of iron than it does, and when the power is cut off, the U-shaped iron rod cannot absorb any iron, and it becomes a new one. Root ordinary iron rod. Sturgeon's electromagnet invention made people see the bright prospect of converting electrical energy into magnetic energy. The invention soon spread in Britain, the United States, and some coastal countries in Western Europe. In 1829, the American electrician Henry made some innovations in the Sterkin electromagnet device. Insulated wire replaces bare copper wire, so there is no need to worry about being short-circuited by excessive copper wire. Since the wires have an insulating layer, they can be wound tightly around a circle. The denser the coil, the stronger the magnetic field generated, which greatly improves the ability to convert electrical energy into magnetic energy. By 1831, Henry tried out a newer electromagnet. Although it was not big, it could suck up 1 ton of iron. The invention of the electromagnet also greatly increased the power of the generator.
5000 years ago, humans discovered natural magnets (Fe3O4)
2300 years ago, Chinese people polished a natural magnet into a spoon shape on a smooth surface. Under the effect of geomagnetism, a spoon handle guide and “Sai Nan” was the first guide instrument in the world.
The Chinese people used magnets and iron needles to rub magnetized 1,000 years ago to make the earliest compass in the world.
Around 1100, China integrated magnet needles and azimuth disks into a magnet-guided instrument for navigation.
1405-1432 Zheng He started a great pioneering move in the history of mankind with a guide meter.
1488-1521 Columbus, Gamma, and Magellan used compasses to conduct world-renowned navigational discoveries.
1600 Englishman William Gibber published his monograph on magnetism. He developed the ancient Greeks Thales, Aristotle and other predecessors of the world on magnetism and experiments.
1785 French physicist C. Coulomb established the "Coulomb's law" describing the interaction between charge and magnetic poles.
1820 Danish physicist H.C. Oster discovered current-induced magnetic force.
1831 British physicist M. Faraday discovers electromagnetic induction.
1873 British physicist J.C. Maxwell completed a unified electromagnetic theory in his monograph "On Electricity and Magnetism."
1898-1899 French physicist P. Curie discovered that the ferromagnetic material became paramagnetism at a specific temperature (Curie temperature).
1905 French physicist P.I. Lang Zhiwan explains the paramagnetic variation with temperature based on statistical mechanics theory.
1907 French physicist P.E. Weiss proposed molecular field theory and extended Lang Zhiwan's theory.
1921 The Austrian physicist W. Pauli proposed that the Bohr magnetite be the basic unit of the atomic magnetic moment. American physicist A. Compton proposed that electrons also have a corresponding magnetic moment of spin.
1928 British physicist P.A.M. Dirac perfectly explained the intrinsic spin and magnetic moments of electrons using relativistic quantum mechanics. And with the German physicist W. Heisenberg to prove the existence of the exchange of electrostatic origin, laid the foundation for the modern magnetics.
In 1936, the Soviet physicist Lang Da completed a masterpiece “A Course in Theoretical Physics,” which contained a comprehensive and beautiful chapter on modern electromagnetism and ferromagnetics.
1936-1948 French physicist L. Nell proposed the concepts and theories of antiferromagnetism and ferrimagnetism, and deepened his understanding of material magnetism in subsequent years of research.
1967 Austrian physicist K.J. Snyder discovers a magnet with high magnetic energy under the guidance of quantum magnetism
The rare earth magnet (SmCo5) opened a new chapter in the development of permanent magnetic materials.
In 1967, Strnat et al. of the University of Dayton, USA, developed a samarium-cobalt magnet, marking the arrival of the era of rare earth magnets.
The second generation of rare earth permanent magnet-Sm2Co17 was introduced in 1974.
1982 Japan's Sumitomo Specialty Metal's Masato Sagawa invented the NdFeB magnet, and the third-generation rare earth permanent magnet-Nd2Fe14B was introduced.
The 1990 atomic-gap magnet-Sm-Fe-N came out.
1991 German physicist E.F. Knelle proposed the theoretical basis for the exchange of two-phase composite magnets, and pointed out the prospects for the development of nanocrystalline magnets.
With the development of society, the application of magnets has become more and more widespread. From high-tech products to the simplest packaging magnets,
At present, the most widely used is neodymium iron boron magnet and ferrite magnet.
From the development history of magnets, in the late 19th century and early 20th century, people mainly used carbon steel, tungsten steel, chromium steel, and cobalt steel as permanent magnetic materials.
In the late 1930s, the successful development of aluminum-nickel-cobalt magnets made possible the large-scale application of magnets.
In the fifties, the appearance of barium ferrite magnets not only reduced the cost of permanent magnets, but also broadened the application of permanent magnetic materials to high-frequency fields.
In the 1960s, the emergence of Samarium Cobalt permanent magnets opened up a new era for the application of magnets. To date, rare earth permanent magnets have undergone the first generation of SmCo5, the second generation of precipitation hardening Sm2Co17, and the development of third generation Nd-Fe-B permanent magnet materials. At present, ferrite magnets are still the most used permanent magnet materials, but the output value of neodymium-iron-boron magnets has greatly exceeded the ferrite permanent magnet materials. The production of neodymium-iron-boron magnets has developed into a large industry.