This was know to ancient Greeks. This is a good way to introduce charge. However, I don't fully understand the mechanism, behind how the charge is separated. The mechanism is not discussed in any standard textbooks. It looks as though the physics is called: triboelectric effect.
This is what the great Feynman says:
Yet in all our long and involved discussion we have never explained why it is thatTo really understand the basic physics of static electricity requires that the students know about atoms. I will briefly discuss atoms and things later on in the course, so now is probably not a good time to add much more detail.
when we rub a piece of amber we get a charge on it. So you see, this physics of ours
is a lot of fakery -- we start out with the phenomena of lodestone and amber,
and we end up not understanding either of them very well.
When I read a few chapters of Five easy lessons by Knight, I see that from Physics Education Research, that many students really only learn the algorithmic nature of the electricity problems. They don't really understand physical principles, such as charge conservation. Also, from the
research quoted in the book -- they don't really understand important things such that an insulator can get charged.
When I was reading a paper called Matter and Interactions by Chabay et al. they claim that the syllabus needs to be made more modern. And that the atomic theory should be used more. They have written a text book, where they use a more modern approach to physics and not this is complementary to physics education research.