Programmable Logic Controller (PLC) Practice Test

An electromechanical relay converts electrical energy into motion to open or close electrical contacts. When current flows through its coil, a magnetic field is produced that pulls a metal armature, causing the contacts to move and switch the load circuit. This combination of electrical input and mechanical movement is what defines an electromechanical relay. Because it relies on a magnetic field created by electricity to drive the mechanical action, it’s not correct to say it uses only mechanical energy. And since it changes the state of a circuit by moving contacts, it can switch currents in the load. It also has moving parts (the armature and contacts), so describing it as having no moving parts would be inaccurate. For contrast, solid-state relays switch without moving parts, but that’s a different type.