The history of electromagnets

 In 1822, French physicists Arago and Lussac discovered that when an electric current passes through a winding with iron in it, it can magnetize the iron in the winding. This was actually the original discovery of the electromagnet principle.

In 1823, Sturgeon also made a similar experiment: he wound 18 turns of bare copper wire on a U-shaped iron rod that was not a magnet rod. The copper coil on the iron rod generates a dense magnetic field, which turns the U-shaped iron rod into an "electromagnet". The magnetic energy on this electromagnet is many times larger than that of the permanent magnet, and it can absorb iron blocks 20 times heavier than it. When the power supply is cut off, the U-shaped iron rod can not absorb any iron blocks, and becomes a new An ordinary iron rod.

Sturgeon's invention of the electromagnet made people see a bright prospect of converting electrical energy into magnetic energy, which soon spread in Britain, the United States and some coastal countries in Western Europe.

In 1829, the American electrician Henry made some innovations to the Sturgeon electromagnet device. The insulated wire replaced the bare copper wire, so there was no need to worry about being too close to the copper wire and short-circuit. Since the wires have an insulating layer, they can be tightly wound together in circles. Since the denser the coils, the stronger the magnetic field generated, which greatly improves the ability to convert electrical energy into magnetic energy.