This project demonstrates the basic principle of an electromagnetic relay using a homemade coil, a metal armature and two separate electrical circuits.
A switch controls the first circuit. When the switch is closed, current flows through the coil and creates a magnetic field. The magnetic field attracts a metal screw, which mechanically closes a second circuit and turns on an LED.
One of the important features of a relay is that the circuit controlling the coil does not need to be electrically connected to the circuit being switched.
Electronics component Fun Kit (with breadboard & power supply module)
General purpose transistors - BC547 (NPN) & BC557 (PNP) pack
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