 Electret

An electret is a dielectric retaining long-lived electric polarization or trapped electric charge after its preparation field is removed. The retained charge distribution can supply a persistent electric field without continuous external polarization power.

An electret condenser microphone uses this property to bias a variable capacitor. Sound moves a diaphragm, changing capacitance and producing an electrical signal in the readout circuit. The electret supplies the polarization condition; it does not provide unlimited electrical energy, and the readout can still require power. Temperature, charge leakage and material history affect long-term stability. ^[ref]

An electret is a dielectric material that has a quasi-permanent electric charge or dipole polarization. It behaves similarly to a permanent magnet, but for electric fields instead of magnetic fields. Electrets are typically made from polymers or ceramics that are electrically polarized during their manufacturing process. Electrets can be used in various applications, including: 1. **Microphones**: Electret condenser microphones utilize electrets to maintain a steady electric field, which helps convert sound waves into electrical signals.