Who decovered the most important electrical effects which is the magnetic effects?

The most important electrical effects, particularly the magnetic effects of electricity, were primarily discovered by Hans Christian Ørsted in 1820. Ørsted demonstrated that an electric current flowing through a wire creates a magnetic field, which was a pivotal moment in the understanding of electromagnetism. This discovery laid the groundwork for further developments by scientists such as André-Marie Ampère and James Clerk Maxwell, who expanded on these concepts.