Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538
Demonstrations are cataloged according to PIRA Bibliography
PLEASE REQUEST DEMOS WELL IN ADVANCE
Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.
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You have selected the following Demos:
video - Xerox
Purpose:To demonstrate the electrostatic principles of Xerox (Photocopier) machine operation.
Set up a metal plate covered with a layer of an insulator (ie. projector transparencies) vertically and connect the metal plate to the ground of the negative Van de Graaff machine. Connect a metallic rake to the dome of the negative Van de Graaff machine.
Turn on the Van de Graaff and slowly spread the charge over the surface of an insulator using the metal rake. Do not let the rake discharge onto the plate by touching it, instead, let it hover over the plate. 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:Don't let the rake discharge as you hover it over the plastic/metal plate. Don't worry about charging whole plate, hover rake over center carefully once/twice should be enough.
When you draw something on plate, make sure you are holding a ground, and you gently touch and drag your finger over the plastic OR you can just use the grounding wand as your drawing tool.
If positive VdG machine is used the polarity of the metal plate and the rake should be reversed.