Piezoelectricity

Apparatus:
There are 3 piezoelectricity demonstrations:

1. 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.
2. Fan type.
   Plug into AC outlet. Two flaps connected to 2 piezoelectric crystals will oscillate at 60 Hz.
3. 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.

Description:
These demonstrations show a change in electric polarization with change in applied stress.