definition of piezoelectric effect
Piezoelectric body is polarized by external mechanical force, which causes bound charges with opposite signs to appear on the two ends of the piezoelectric body. The charge density is proportional to the external mechanical force. This phenomenon is called the positive piezoelectric effect. The electric body is deformed by the external electric field, and its deformation is proportional to the intensity of the external electric field. This phenomenon is called the inverse piezoelectric effect. A solid with a positive piezoelectric effect must also have an inverse piezoelectric effect, and vice versa. The positive and negative piezoelectric effects are collectively called piezoelectric effects. Whether a crystal has a piezoelectric effect is determined by the symmetry of the crystal structure.