electret

electret, 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...