The Englishman Michael Faraday (1791-1867) has always researched the connection between electricity and magnetism. He was a physicist and a chemist, but he had a difficult theoretical background, so he valued the experience he acquired and also the proof of natural phenomena. Thanks to his intense and methodical experiments, in 1822 he was able to demonstrate what a circular magnetic field was.
At the beginning of this search, the Danish Hans Christian Öersted (1777-1851) did not conceive that his simple experience would uncover the fundamental physical principle for the operation of the electric motor. https://www.mrosupply.com/motors/ac-motors/general-purpose-motors/jet-pump-motors/2526201_12099600_leeson/ He started by passing an electric current generated by a pile through a conductor wire and then brought a compass to that wire. As a result the needle, which is a magnet, moved and aligned perpendicular to the thread. This event confirmed that there was a magnetic field around the wire. The relation between electricity and magnetism was thus established for the first time.
Later the French physicist André-Marie Ampère (1775-1836), a mathematical genius, after learning about Öersted’s experiences, began to formulate the law of electromagnetism, concluding that the lines of force created by the electrified wire – the magnetic field – they are circular, that is, they form a sort of invisible cylinder around the driver.