I created this transistor prop to help explain how a Bipolar Transistor works. The design has two main parts: the base and the lever arm.
The lever arm represents the amplification of the transistor using water flow as current.
A little water flow at the base flap lifts the emitter-collector flap much higher allowing more water (current) to flow.
Full explanation is in my Video: https://youtu.be/RI-7TyVWB3s
The waveform stl file has DC and AC representations as seen in the video.