This video shows you how to build a really sensitive glow in the dark circuit that reacts to shadows and slight changes in light. The reason it is so sensitive is that the changes in the current flow through the LDR are multiplied by 40 enabling the LED to be turned on and off by mere shadows.
Also the reason for the 10K variable resistor is that you can build this circuit with almost any kind of LDR
•Light Dependent Resistor
•Variable Resistor 1KΩ
p.s: too easy for ya?, well its a part of a free, fully documented (programs+schematics) online course designed to get young kids into electronics, so if you think it's any good pass it on?
Download Handout Below: