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Purpose:To demonstrate the electrostatic principles of Xerox machine operation.
Procedure:Set up a metal plate covered with a layer of an insulator (z.B. projector transparencies) vertically and connect the metal plate to the ground of the negative Van der Graaf machine. Connect a metallic rake to the ball of the negative Van der Graaf machine.
Turn on the Van der Graaf and slowly spread the charge over the surface of an insulator using the metal rake. Ground yourself nicely (by holding a ground cable for example) and use your finger to draw something on the transparency. If everything is done right you will feel slight crackling under your finger tips.
Finally sprinkle some chalk dust (slapping two board erasers works the best) and see the dust sticking to the contours of the drawn symbol.
Hints:If positive VdG machine is used (the one with the blue base) the polarity of the metal plate and the rake should be reversed.
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