In 1822, French physicists Arago and Lyssac discovered that when an electric current passes through a winding with iron blocks inside, it can magnetize the iron blocks in the winding. This is actually the initial discovery of the principle of electromagnets.

In 1823, Sturgeon also conducted a similar experiment: he wound 18 turns of bare copper wire on a U-shaped iron rod that was not a magnetic rod. When the copper wire was connected to the photovoltaic battery, the copper wire wound around the U-shaped iron rod generated a dense magnetic field, which turned the U-shaped iron rod into an "electromagnet". The magnetic energy on this type of electromagnet is much greater than that of a permanent magnet. It can absorb iron blocks that are 20 times heavier than it, but when the power is cut off, the U-shaped iron bar cannot absorb any iron blocks and becomes a regular iron bar again. Sturgeon's invention of electromagnets opened up bright prospects for converting electrical energy into magnetic energy, which quickly spread to the UK, the United States, and some coastal countries in Western Europe.

In 1829, American electrician Henry made some innovations to the Sturgeon electromagnetic device, replacing bare copper wires with magnetoelectric insulated wires, so there was no need to worry about being too close to the copper wires and causing a short circuit. Due to the insulation layer on the wires, they can be tightly wound together in circles. The denser the coils, the stronger the magnetic field generated, greatly improving the ability to convert electrical energy into magnetic energy.

In 1831, Henry developed a newer electromagnet, which, although not large in size, could lift a ton of iron.

Inspired by the Auster current magnetic effect experiment and a series of other experiments, Ampere realized that the essence of magnetic phenomena is current, and attributed various interactions involving current and magnets to the interactions between currents. He proposed the basic question of finding the law of interaction between current elements. In order to overcome the difficulty of isolated current elements being unable to be directly measured, Ampere carefully designed four zero indication experiments accompanied by rigorous theoretical analysis, and obtained the results. However, because Ampere holds the concept of Action at a distance on electromagnetic action, he once imposed the assumption that the force between two current elements is along the line in theoretical analysis, expecting to obey Newton's third law, which made the conclusion wrong. The above formula is the result of discarding the assumption of incorrect forces along the connecting line and correcting it. It should be understood from the perspective of close range action that the current element generates a magnetic field, which exerts a force on another current element.