noun Electricity.
a dielectric that possesses a permanent or semipermanent electric polarity, analogous to a permanent magnet.

1880–85; electr(icity) + (magn)et

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World English Dictionary
electret (ɪˈlɛktrət)
a permanently polarized dielectric material; its electric field is similar to the magnetic field of a permanent magnet
[C20: from electr(icity + magn)et]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Encyclopedia Britannica


material that retains its electric polarization after being subjected to a strong electric field. The positive charge within the material becomes permanently displaced in the direction of the field, and the negative charge becomes permanently displaced in the direction opposite to the field. One end of the electret is somewhat positive, and the other is somewhat negative, though the net charge remains zero. Electrets are prepared from certain waxes, plastics, and ceramics, the individual molecules of which are permanently polarized but are randomly arranged before being subjected to an electric field so that there is no overall polarization in the material. The strong electric field (approximately 1,000,000 volts per metre) rotates the polar molecules into an alignment that persists when the external field is removed. Sometimes electrets are made by allowing a molten material to solidify in a strong electric field.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Electret filters use electrically charged media to attract particles.
There are two types of condenser microphones: conventional and electret.
In contrast to the electrostatically enhanced filter, electret media are permanently charged in the course of manufacturing.
The electret microphone revolutionized the microphone industry, with almost one billion manufactured each year.
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