Electret
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Electret (formed of elektr- from "electricity" and -et from "magnet") is material that has been permanently electrically charged (polarised). The magnetic equivalent is a permanent magnet. Oliver Heaviside coined this term.
Polarised material consists of atoms or molecules with electric dipole moment. It can be produced by cooling down material composed of long molecule chains with electric dipole moment so that so-called domains are formed.
Electret materials have recently found commercial and technical interest. For example, they are used in one form of microphone.
Further reading
- Jefimenko, Oleg D., and David K. Walker (illus.), "Electrostatic motors; their history, types, and principles of operation". Star City [W. Va.], Electret Scientific Co. [1973]. LCCN 73180890
- Adams, Charles K., "Nature's Electricity". Tab Books, Inc., Pa. (USA). ISBN 0830627693
- Gross, Bernhard, "Charge storage in solid dielectrics; a bibliographical review on the electret and related effects". New York, Elsevier Pub. Co., 1964. (Supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under grants number AF 60-6 and 61-140.)