In 1822, the French physicists Arago and Lussack discovered that when the current passed through the winding of the iron block, it could make the iron in the winding magnetic.
The magnet is magnetized. This is actually the initial discovery of the electromagnet principle.
In 1823, Sturgeon did a similar experiment: he wrapped 18 turns of bare copper wire on a U-shaped iron bar that was not a magnet bar. When the copper wire was connected to the voltaic cell, it was wound around U. The copper coil on the iron rod creates a dense magnetic field, which turns the U-shaped iron rod into an "electromagnet". The magnetic energy on this electromagnet is more than doubled than that of the permanent magnet. It can suck up an iron block 20 times heavier. When the power is cut off, the U-shaped iron bar can't hold any iron. Root ordinary iron rod. The invention of Sterling's electromagnets led to the bright future of converting electrical energy into magnetic energy, a invention that soon spread in the United Kingdom, the United States, and some coastal countries in Western Europe.
In 1829, the American electrician Henry made some innovations on the Sterling electromagnet device. The insulated wires replaced the bare copper wires, so there was no need to worry about being short-circuited by the copper wires being too close. Since the wires have an insulating layer, they can be tightly wound together in a circle. The denser the coil, the stronger the generated magnetic field, which greatly improves the ability to convert electrical energy into magnetic energy. By 1831, Henry had prototyped a newer electromagnet. Although it was not large, it could suck up a ton of iron. The invention of the electromagnet also greatly improved the power of the generator.
development path
5,000 years ago, humans discovered natural magnets (Fe3O4)
2300 years ago, the Chinese used a natural magnet to be scooped on a smooth surface. Under the action of geomagnetism, the guide of the spoon handle, 曰 "Si Nan" is the world's first guide.
1000 years ago, the Chinese used magnets and iron needles to frictionally magnetize them to make the world's first compass.
Around 1100, China integrated the magnet needle and the azimuth plate into a magnet-type guide for navigation.
1405-1432 Zheng He began his great pioneering work in the history of mankind with his guide.
1488-1521 Columbus, Gamma, Magellan used the compass to carry out a world-famous maritime discovery.
1600 British William Gilbert published a monograph on magnetism, "Magnet," which developed the understanding and experimentation of magnetism by ancient Greeks such as Thales and Aristotle.
1785 French physicist C. Coulomb used the twist to establish the "Coulomb's law" describing the force between the charge and the pole.
1820 Danish physicist H.C. Oster found that current induced magnetic force.
1831 British physicist M. Faraday discovered the phenomenon of 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 ferromagnetic materials become paramagnetic at specific temperatures (Curie temperature).
1905 French physicist P.I. Lang Zhiwan explained the paramagnetic variation with temperature based on statistical mechanics theory.
1907 French physicist P.E., who proposed molecular field theory, extended Lang's theory.
1921 Austrian physicist W. Pauli proposed the Bohr magnetron as the basic unit of atomic magnetic moment. American physicist A. Compton proposed that electrons also have spin-corresponding magnetic moments.
1928 British physicist P.A.M. Dirac uses the theory of relativistic quantum mechanics to perfectly explain the intrinsic spin and magnetic moment of electrons. Together with the German physicist W. Heisenberg, it proves the existence of the exchange power of the origin of static electricity and lays the foundation of modern magnetism.
In 1936, the Soviet physicist Lang Dao completed the masterpiece "The Course of Theoretical Physics", which contains a comprehensive and wonderful chapter on modern electromagnetics and ferromagnetism.
1936-1948 French physicist L. Neel proposed the concepts and theories of antiferromagnetic and ferrimagnetic, and deepened the understanding of material magnetism in subsequent years of research.