What does a standard relay commonly use to function?

A standard relay operates primarily on the principle of magnetic fields. When an electrical current flows through the coil of the relay, it generates a magnetic field that attracts a movable armature within the relay. This movement opens or closes contacts, allowing the relay to control a circuit without the need for direct electrical connection. The reliance on magnetic fields is crucial for the relay's ability to switch circuits efficiently and safely, making it a fundamental element in various electrical applications.

In contrast, thermal sensors are used in devices where temperature detection is key, while capacitive changes pertain to circuits reliant on variations in electric charge. Friction is not a principle utilized in the operation of relays; instead, it is more associated with mechanical devices that rely on physical contact and movement. Thus, the use of magnetic fields in relays is essential for their functionality in electrical systems.