In 1820, who found that electric current causes a nearby magnetic needle to move and thus discovered electromagnetism?

Hans Christian Oersted

The correct answer is option 3. Hans Christian Oersted.

Hans Christian Oersted's discovery of electromagnetism in 1820 marked a significant breakthrough in the understanding of the relationship between electricity and magnetism. Oersted was a Danish physicist and chemist who conducted an experiment that led to this discovery.

In his experiment, Oersted observed the deflection of a magnetic needle placed near a wire carrying an electric current. Prior to this experiment, it was commonly believed that electricity and magnetism were distinct phenomena that did not interact with each other. However, Oersted's experiment demonstrated otherwise.

When Oersted passed an electric current through a wire, he observed that a nearby magnetic compass needle was deflected from its original orientation. This observation indicated a direct relationship between electric current and magnetic fields. Oersted concluded that an electric current produces a magnetic field around the wire, and the interaction between this magnetic field and the magnetic needle caused its deflection.

Oersted's discovery of electromagnetism laid the foundation for the development of electromagnetic theory, which was further advanced by physicists such as André-Marie Ampère and Michael Faraday. It eventually led to James Clerk Maxwell's formulation of Maxwell's equations, which unified electricity and magnetism into a single theory of electromagnetism.

The discovery of electromagnetism has had profound implications in various fields, including physics, engineering, and technology. It laid the groundwork for the development of electric motors, generators, transformers, and other devices that are essential to modern technology. Oersted's experiment remains a classic example of how a simple observation can lead to groundbreaking discoveries in science.