The electrostatic pinwheel is an experiment where a wheel with radially aligned spikes is turning like they were jets and matter was being pushed out of the ends. It works by charging the surrounding air (corona discharge) with the same charges and then repelling from the like-charged air cloud (which is also getting blown in the opposite direction).

As far as I understand, negatively charged pinwheel throws out some electrons (photoelectric effect) making the nearby air negative. Positively charged spikes ionize the surrounding air and pull in some electrons making the air negative. However, both of these charging mechanism seem to rely on air being there to be repelled from.

Would this device turn in vacuum? The spikes would still have greater electric field than the rest of the surface. It might make electrons be thrown out. Does it mean it could turn as a jet accelerating electrons and slightly getting accelerated by electrons? Or is the mass of electron too tiny to give noticable momentum and overcome any realistic friction?

And what about the positive case? Could it work as a ion jet? It should probably mean a higher threshold and more work on exiting material, but as a result the electric field would be higher and exiting charge would be heavier - maybe that's even better for a jet engine?

  • $\begingroup$ This video explains how it works, and no, it needs air to ionize, and there is no photoelectric effect. youtube.com/watch?v=yU94HVCNbGA $\endgroup$ – anna v Dec 10 '17 at 6:56
  • $\begingroup$ @annav The explanation in the video focuses on the positive case which draws electrons into material. Negatively charged spikes would have to push out electrons or pull positive ions of air molecules. As far as I know, it's actually the former and it is actually photoelectric effect by photons generated mainly by the recombinations in the surrounding gas. However, my question was not if the same mechanism would work in the vacuum, but if the wheel would still spin (maybe slower and nedding higher potential) by pure jet-like mechanism or not? $\endgroup$ – Džuris Dec 10 '17 at 7:12
  • $\begingroup$ how could it when it depends on ions? $\endgroup$ – anna v Dec 10 '17 at 7:43
  • $\begingroup$ @annav by the surface electric field detaching electrons or ions from surface and repelling from them. I don't know if that would actually happen but it seems plausible and so I'm asking. I've seen multiple people guessing at first that the electrostatic pinwheel works by expelling charged particles like a jet engine. While it's not true in the usual case, might it be the case in vacuum? $\endgroup$ – Džuris Dec 10 '17 at 7:55
  • $\begingroup$ vacuum means by definition that there are no atoms to ionize, it is the air atoms they are talking about, interacting with the atomos of the of the blades . The blades by themselves are no good $\endgroup$ – anna v Dec 10 '17 at 8:35

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