What does a deflected needle indicate in the context of electricity and magnetism?

In the context of electricity and magnetism, a deflected needle typically refers to the movement of a magnetic needle or compass needle in response to an electric current. This phenomenon was first observed by Hans Christian Ørsted in 1820 and is a fundamental principle in electromagnetism.

If a current-carrying conductor is placed near a magnetic needle, the needle will experience a deflection from its usual north-south alignment. Ørsted’s experiment demonstrated that an electric current produces a magnetic field around the conductor. The deflection of the needle indicates the presence and direction of the magnetic field generated by the current.

The key takeaway is that an electric current creates a magnetic field, and the interaction between electric currents and magnetic fields is a fundamental principle in electromagnetism. This discovery by Ørsted laid the foundation for the development of various technologies, including electric motors, generators, and many other applications in electrical engineering.