There are 3 piezoelectricity demonstrations:
- Spark between 2 points.
Turn crank handle with caution so as not to break the crystal. Sparks are generated with compression, and again with release.
- Fan type.
Plug into AC outlet. Two flaps connected to 2 piezoelectric crystals will oscillate at 60 Hz.
- Hand held type.
Hold crystal frame such that it can flex. An attached light bulb has two filaments. One of the filaments will light up with a flex in one direction, and the other will light when the crystal is flexed in the opposite direction.
These demonstrations show a change in electric polarization with change in applied stress.