What is the purpose of a relay in an electrical system?

The purpose of a relay in an electrical system is to switch electronic circuits on or off. Relays are essentially electrically operated switches that allow a low power signal to control a larger power circuit without direct electrical contact. When an electrical current flows through the coil of the relay, it generates a magnetic field that pulls an armature, either closing or opening a set of contacts. This process enables the relay to control high-voltage or high-current circuits while being managed by a low voltage signal, making them essential for various applications, including HVAC systems, where they might control motors, compressors, or other components based on the system's operational needs.

In this context, the other options do not accurately represent the primary function of a relay. For example, increasing signal strength pertains more to devices like amplifiers, voltage regulation involves stabilizing voltage levels in power supply systems, and storing electrical energy is typically the role of capacitors or batteries. Therefore, the correct identification of a relay's role as a device that switches circuits highlights its importance in controlling and managing electrical systems efficiently.