What is the role of a relay in a circuit?

A relay plays a critical role in controlling a circuit using another electrical circuit. It acts as an electrically operated switch, whereby a small input signal can control a larger load. When current flows through the coil of the relay, it generates a magnetic field, which closes the contacts and allows a different circuit to be energized or de-energized. This capability makes relays extremely useful for automating control processes, providing safety mechanisms, or isolating control circuits from high power circuits.

The understanding of a relay's function is foundational in electrical engineering and automation, as it allows for the control of high voltage or high current devices using low voltage signals. This is particularly important in applications where a direct electrical connection may not be feasible or safe.