Electrical charges within their structures stop cancelling out each other - a potential is generated
Using the image below representing crystal structure:
Locate "the center of the positive charges" and mark it with a +
Locate "the center of the negative charges" and mark it with a -
Note that the two centers overlap.
Image source: Slide 4 from the presentation available at this link by Nuthan Raju V., Karthik T.P, Mohd Jaffar Ahmed Khan of the M.S.Ramaiah School of Advanced Studies
Using the image below representing crystal structure:
Locate "the center of the positive charges" and mark it with a red +
Locate "the center of the negative charges" and mark it with a blue -
The procedure is similar to finding a balance for "weights".
Note that the two centers no longer overlap. Two poles emerge, a negative and a positive. A dipole (di--> two) is created.
Image source: Slide 5 from the presentation available at this link by Nuthan Raju V., Karthik T.P, Mohd Jaffar Ahmed Khan of the M.S.Ramaiah School of Advanced Studies
Excerpt (english link):
The first demonstration of the direct piezoelectric effect was in 1880 by the brothers Pierre Curie and Jacques Curie. They combined their knowledge of pyroelectricity with their understanding of the underlying crystal structures that gave rise to pyroelectricity to predict crystal behavior, and demonstrated the effect using crystals of tourmaline, quartz, topaz, cane sugar, and Rochelle salt (sodium potassium tartrate tetrahydrate). Quartz and Rochelle salt exhibited the most piezoelectricity.
Left: « PierreCurie » par Nobel Foundation http://nobelprize.org/nobel_prizes/physics/laureates/1903/pierre-curie-bio.html. Sous licence Domaine public via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:PierreCurie.jpg#/media/File:PierreCurie.jpg
Right: « Curie1895These » par Pierre Curie (1859-1906) — Leiden University Library. Sous licence Domaine public via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Curie1895These.jpg#/media/File:Curie1895These.jpg
Curie brothers and their parents
Image source link (interesting blog in French)
The converse effect was mathematically deduced from fundamental thermodynamic principles by Gabriel Lippmann in 1881. The Curies immediately confirmed the existence of the converse effect, and went on to obtain quantitative proof of the complete reversibility of electro-elasto-mechanical deformations in piezoelectric crystals.
As a consequence of the converse effect, if you apply electricity on a crystal you can flex it/bend it. If you apply an alternating current, you can make the crystal move back and forth or oscillate.
A crystal that oscillates makes adjacent (air) molecules oscillate and generates a sound wave.
Depending on the current that you apply you can induce oscillation of the crystal at different frequencies e.g. if above 20.000Hz you generate ultrasound.
In (quartz) clocks and watches, the frequency is usually 32,768 Hz, and the crystal is cut in a small tuning fork shape on a particular crystal plane. This frequency is a power of two (32,768 = 215), just high enough so most people cannot hear it, yet low enough to permit inexpensive counters to derive a 1-second pulse.
Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses
"Sonar Principle EN" by Georg Wiora (Dr. Schorsch) - Self drawn with Inkscape. Licensed under CC BY-SA 3.0 via Commons https://commons.wikimedia.org/wiki/File:Sonar_Principle_EN.svg#/media/File:Sonar_Principle_EN.svg
To measure the distance to an object, the time from transmission of a pulse to reception is measured and converted into a range by knowing the speed of sound.
Interesting link: http://oceanservice.noaa.gov/facts/sonar.html
A sound wave is typically produced by a piezoelectric transducer encased in a plastic housing. Strong, short electrical pulses from the ultrasound machine drive the transducer at the desired frequency. The frequencies can be anywhere between 1 and 18 MHz.
The sound wave is partially reflected from the layers between different tissues or scattered from smaller structures. Specifically, sound is reflected anywhere where there are acoustic impedance changes in the body: e.g. blood cells in blood plasma, small structures in organs, etc. Some of the reflections return to the transducer.
The return of the sound wave to the transducer results in the same process as sending the sound wave, except in reverse. The returned sound wave vibrates the transducer and the transducer turns the vibrations into electrical pulses that travel to the ultrasonic scanner where they are processed and transformed into a digital image.
"Embryo at 14 weeks profile" by X.Compagnion (cropd by Hidro) Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Embryo_at_14_weeks_profile.JPG#/media/File:Embryo_at_14_weeks_profile.JPG
Japan harnesses energy from footsteps
Train stations in Tokyo are harnessing the energy of legions of commuters to power advertising hoardings and ticket machines.
(reference for 1 and 2: https://en.wikipedia.org/wiki/Piezoelectricity)
Collagen is the main structural protein in the extracellular space in the various connective tissues in animals. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content.
Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin. It is also abundant in corneas,cartilage, bones, blood vessels, the gut, intervertebral discs and the dentin in teeth.
By chewing we generate electricity which helps in the well-being of our jaws etc.
Pineal gland: our built in wireless-transmitter?