Describe the function of a relay in electrical applications.

A relay serves the essential function of opening or closing a circuit in response to an electrical signal. It acts as an electromechanical switch that allows a small electrical current to control a larger one. When an electrical signal is applied to the coil of the relay, it creates a magnetic field that moves a switching mechanism. This action can either complete a circuit, allowing current to flow, or break a circuit, stopping the current flow, thus controlling the operation of various electrical devices or systems.

In practical applications, relays are widely used in automotive systems, automated equipment, and in remote control systems, where they provide the ability to control high voltage or high current loads with low power signals, ensuring safety and efficiency. This functionality is crucial in applications that require isolation between the controlling and controlled circuit while also managing the electrical load.