Piezoelectric Effect
Sounds accompany the discharges of electricity.
A piezoelectric crystal is connected to a light bulb. When the crystal is pressed, the light flashes.
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Keywords
electricity, crystal lattice, electrical properties of matter, solid state, solids and liquids, electronic structure, periodic table,
Multimedia
Part 1 of 2
_Play movie (8 seconds, 0.5 MB)
When a piezoelectric crystal is pressed or released, it produces a voltage.
Part 2 of 2
_Play movie (8 seconds, 0.5 MB)
Stress in the crystal is relieved when electricity is allowed to flow.
Different versions of the movies:
The click produced by the current is not very loud and might be missed while the viewer is focusing on the narration. Here are versions of the movie with different sound tracks to allow exploration.
Part 1 with sound effects
only
Part 1 with voice-over
only
Part 1 with both voice-over
and sound effects
When a piezoelectric crystal is pressed or released, it produces a
voltage.
Part 2 with sound effects
only
Part 2 with voice-over
only
Part 2 with both voice-over
and sound effects
Stress in the crystal is relieved when electricity is allowed to
flow.
Discussion
When pressure is applied to a piezoelectric material such as quartz (SiO2), the crystal deforms in such a way as to create an electric dipole moment, generating an electric current. Releasing pressure will also produce a current. Piezoelectric crystals are used in the strikers of lighters to generate a spark.
The complementary effect is also observed. When a voltage is applied across a piezoelectric material, the crystal deforms.
These movies have been provided at 30 frames per second. This was done to present the sound and the flash of the piezoelectric device. It is expected that some computers will not be fast enough to always present all of the frames to the viewer. If you do not see the flash when you hear the sound, you might replay the movie or use the scroll device to locate the flash.
Additional still images for this topic
Demonstration Notes: Warnings, Safety Information, etc.
Exam and Quiz Questions
1. Would you expect the bonds in a piezoelectric substance to be polar or nonpolar? Explain.
2. How does deforming the crystal lattice of a piezoelectric substance generate a current?