This kit is an interesting conductive experiment to demonstrate sound, light and electricity. When the metal horn nail on the shaft contacts with the conductive iron wire, the power supply, buzzer and LED light form a path, the circuit is switched on, and the LED light and buzzer sound. When the horn nail on the shaft does not contact with the conductive iron wire, it will form a break, then the circuit is disconnected and the buzzer and LED lamp do not work. A great and fun wait to learn about conductivity and circuits!