On what principle do electric relays operate?

Electric relays operate on the principle of magnetism. Specifically, they utilize an electromagnetic mechanism to control the opening and closing of contacts in a circuit. When an electric current flows through the coil of the relay, it creates a magnetic field that attracts a movable armature. This movement either completes or interrupts an electrical circuit, allowing the relay to function as a switch. This magnetism is pivotal because it enables the relay to operate remotely, controlling high power circuits with a lower power signal without direct electrical contact.

Friction, gravity, and electricity do not play a direct role in the fundamental operation of relays. Friction relates to mechanical systems and can introduce wear but is not a working principle for relays. Gravity influences certain mechanical devices and systems, but it is not relevant here. Electricity, while essential as a power source and operational medium, serves as the energy that generates the magnetic field rather than as the primary principle of operation. Therefore, magnetism is the key principle underlying the functionality of electric relays.