The discovery that a current-carrying wire generates a magnetic field is attributed to the Danish physicist Hans Christian Ørsted. In 1820, Ørsted was conducting a lecture demonstration on the relationship between electricity and magnetism when he made an accidental observation that revolutionized the understanding of electromagnetism.
During the lecture, Ørsted noticed that when he passed an electric current through a wire connected to a battery, a nearby magnetic compass needle deflected from its original position. This observation indicated that an electric current in a wire was somehow producing a magnetic effect.
Ørsted further experimented and confirmed that the deflection of the compass needle was directly related to the flow of electric current. He found that the magnetic field produced by the current-carrying wire followed a circular pattern around the wire, with the direction of the field determined by the right-hand rule (also known as the Ampere's right-hand grip rule).
This accidental discovery laid the foundation for the understanding of electromagnetism and eventually led to the development of important scientific principles and technologies, including electromagnetic induction, electric motors, and generators. It also formed the basis for the work of other notable scientists, such as André-Marie Ampère, who expanded on Ørsted's findings and developed mathematical formulations for calculating the magnetic field produced by a current-carrying wire.
The discovery of the magnetic field around a current-carrying wire played a significant role in the unification of electricity and magnetism, leading to the development of the theory of electromagnetism and shaping the field of physics as we know it today.