All ferroelectric materials exhibit piezoelectricity a piezoelectric effect. Accelerometers based upon piezoelectricity are constructed with two piezoelectric transducers. Ferroelectrets display strong piezoelectricity, comparable to ceramic piezoelectric materials. The most widely used transduction principles are electromagnetism, electrostatics and piezoelectricity. Electric motors operate on three different physical principles&colon; magnetism, electrostatics and piezoelectricity. French physicists Jacques and Pierre Curie discovered piezoelectricity in 1880. Ceramics with randomly oriented grains must be ferroelectric to exhibit piezoelectricity. Brothers Pierre and Jacques Curie discovered piezoelectricity in Rochelle salt circa 1880. Quartz and Rochelle salt exhibited the most piezoelectricity. Electrostriction is a quadratic effect, unlike piezoelectricity, which is a linear effect. This method utilises the concept of piezoelectricity to obtain a grating. Direct piezoelectricity of some substances, like quartz, can generate potential differences of thousands of volts. PVDF exhibits piezoelectricity several times greater than quartz. This characteristic is called electrostriction or inverse piezoelectricity. This propelled a number of developing applications on piezoelectricity and pyroelectricity.