5.4 Piezoelectricity Electricity can be generated by exerting pressure on a crystal. A special kind of substance, the piezo electric crystal, converts mechanical energy into electric energy when pressure is exerted on it. Once a piezo electric crystal that is connected to a neon lamp is struck with a mallet, the neon lamp will emit a brief flash of light. A small portion of the mechanical energy is converted into electricity. Most of the energy is again transformed into heat. Fig. 5.4.1 illustrates the set-up. Piezo is a Greek word for pressure. Piezo electric crystals are made of such compounds as quartz, Rochelle salt, tour-maline and barium titanate. Usually the opposite sides of the crystal are silver plated and thin, flexible copper leads soldered to the plated area. When a steady pressure is applied, no electric energy is generated. The voltage produced by piezo electric crystal is very small and cannot be measured by a voltmeter. It requires to be amplified. Piezo electric cryst...