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This is a piece of aluminum foil which is at approximately 24,000 Volts. It is energized by a flyback transformer from an old computer moniter. NOTE - HIGH VOLTAGE IS VERY DANGEROUS DO NOT ATTEMPT THIS AT HOME - Unless you know how to do it safely!
So the voltage is the same at all points on the pinwheel but the voltage per centimeter is greater at the points of the pinwheel. So ions are being pushed at the points. Many of the ions are from the air but virtual ions from quantum fluctuations of empty space may also get pushed. See the article by Hal Puthoff on the Weird Science page. Higher voltages may give the pinwheel bigger pushes!