A very simple device to convert light into sound can be made by wiring a solar cell directly to headphones (or an earpiece). The solar cell converts light into electricity and the headphones convert electricity into sound. The limitation...

Strike a key on the piano, and you hear the string vibrating. Just about any object vibrates when it's knocked, but how much and how fast? This project helps you find out. You'll build a simple light-sensing circuit for measuring the...

A simple demonstration is described which shows how a transistor works. By including the audience into the actual circuit and by lighting LED's it shows the potential of the simple transistor amplifier. The extension to two transistors -...

With the help of some economics metaphors, Habitat Network delves into the scary-sounding "ecological trap" and helps bring it to light.