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

The primary purpose of using a relay in an electrical circuit is to switch the circuit on and off electrically. A relay acts as an electromechanical switch that uses an electromagnetic coil to control the opening and closing of a set of contacts. When a small control voltage is applied to the coil, it generates a magnetic field that moves an armature, either connecting or disconnecting the electrical circuit. This allows for controlling high-power devices with a low-power signal, making relays essential in various applications such as automation, safety systems, and remote control.

While other options mention functions related to electrical circuits, they do not capture the core purpose of a relay effectively. For instance, increasing voltage levels typically involves transformers, measuring current flow involves instruments like ammeters, and reducing energy loss pertains to optimizing designs rather than the primary function of a relay. The fundamental characteristic of a relay is its ability to act as a switch, which is central to its application in controlling electrical circuits.