What is the main function of a relay in an electrical circuit?

A relay primarily serves the function of controlling a high-power circuit using a low-power signal. This is essential in many applications where it is necessary to operate devices that require a significant amount of power, such as motors or large lighting systems, without needing to handle the high voltage or current directly in the control circuitry.

The operation of a relay involves an electromagnetic switch that is activated by a low-power input signal. When the signal energizes the relay's coil, it creates a magnetic field that closes the contacts of the relay, allowing a larger current to flow through the circuit connected to those contacts. This allows the system to efficiently manage power without exposing the control components to high voltages or currents, thereby enhancing safety and efficiency in electrical design.

While relays can provide some level of isolation between the control circuit and the high-power circuit, their primary purpose is not to achieve complete isolation. Additionally, relays do not function to increase voltage levels or measure electrical resistance, which are roles fulfilled by other types of electrical devices or components.