What is the primary function of a relay in a circuit?

A relay primarily functions as an electrically operated switch. It consists of an electromagnet that, when energized, creates a magnetic field that opens or closes a set of contacts. This allows a low-power control signal to control a higher power circuit, enabling the relay to act as an intermediary that switches the current flow on or off, depending on whether the relay's coil is energized.

This is particularly useful in automation and control systems where low-power signals from sensors or control systems need to operate larger loads, such as motors or lighting. The electromagnetic nature of the relay allows for remote control of devices without the need for manual intervention.

In contrast, changing AC to DC is a function of rectifiers, amplifying signals pertains to operational amplifiers or transistors, and measuring current involves the use of ammeters or current sensors. Each of these functions serves a different purpose in electronics and does not align with the primary role of a relay.