What is the function of a relay?

A relay functions primarily as a switch that is activated by a low-power signal to control a higher-power circuit. This is particularly useful in various electrical systems where the low-power control mechanism can turn on or off larger electrical loads without the need for direct human intervention or high-power control devices.

When the low-power signal energizes the relay's coil, it creates a magnetic field that closes or opens the contacts within the relay, thereby completing or breaking the high-power circuit. This allows for safe and efficient control of appliances, motors, and other electrical devices that require more power than can be provided directly by the control circuit itself.

Other options present functions that relays do not perform. For instance, relays do not inherently increase voltage in a circuit; their primary purpose revolves around switching rather than voltage transformation. Similarly, while fuses and circuit breakers protect against overload, relays do not provide this protective function. Measuring electrical current is the role of ammeters or current sensors, not relays, which are designed for switching actions rather than measurement. Thus, the ability of a relay to facilitate control over high-power circuits using low-power signals is what makes it an essential component in many electrical systems.