What is the working principle of the relay?

What is the working principle of the relay?

Relays generally refer to electromagnetic relays, which are mechanical actions. The essence of the relay is to use a loop (usually a small current) to control the on and off of another loop (generally a large current), and in this control process, the two loops are generally isolated, and its basic principle is to utilize The electromagnetic effect is used to control the mechanical contact to achieve the purpose of switching, and the core coil is energized - the coil current generates a magnetic field - the magnetic field absorbs the armature action switching contact, and the whole process is "small current - magneto-mechanical - large current" a process