What is a relay or solenoid?

A relay is an electromechanical switch that uses an electromagnet to control the opening and closing of a circuit. When an electric current passes through the coil of the relay, it generates a magnetic field that activates a lever mechanism, allowing the switch to open or close. A solenoid, on the other hand, is a type of electromagnet that produces linear motion when an electric current flows through its coil, typically used to push or pull a plunger. Both devices are essential in automation and control systems.