So, magnets have permanent magnetic fields and electrets have a permanent electric field. Note that this is completely different than an electromagnet that generates a magnetic field due to an electric current. It seems like the main uses for these things are as sensors in microphones and dust collectors in air filters, but I think they have more potential, they just don't get the same attention that their magnetic counterparts do. They are made in an analogous way to ceramic magnets. A highly dielectric material melt is cooled and solidified in a strong electric field which aligns the molecules in the solid creating a permanent electric field.
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