Would it be possible to create an electret compass? Would it be possible to create an electret compass (to detect an electric field, for instance, from a Van de Graaff generator)? Thanks.
 A: Like @jopheph h 's answer above, the answer is yes, but it probably wouldn't be that useful. For a regular compass, the magnetized needle is balanced fairly carefully and there is little friction.  The needle can also be fairly long. You can then figure out the torque that is exerted on the needle.
You could do the same with an electret, but often the distance between the positive and negative surfaces are relatively small. This is because usually one surface has the fixed charge embedded from the corona fo a plasma.
But you could try to increase the distance between the positive and negative by embedding positive charge in one end of a bar of an insulating material and negative charge in the other end of the insulating bar. This would be more similar to a bar magnet of needle used in a compass. This would increase the magnitude of the electret dipole and would work more like a regular compass.
However, if you put it in a box of metal, then the metal would act as a faraday shield and the electret wouldn't see the external field.
A: Can't see why not. The way an electret behaves in an electric field is analogous to the way a magnet behaves in a magnetic field.
An electret has an electric dipole polarization and will line up along the direction of an electric field (with the  positively charged end pointing in the direction of the electric field).
The material electrets are made of allows them to retain an electric polarization (after being put in a relatively strong electric field they retain a (quasi) permanent electric field).
This will allow it to line up with any other electric field, telling you its direction, similar to what a compass does in a magnetic field.
