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Code Number: 5B10.25
Demo Title: Van de Graaff - Plates & Peanuts, Felt Bat
Condition: Good
Principle: Electrostatics
Area of Study: Electricity & Magnetism
Equipment:
Van de Graaff Generator, Stack of Pie Tins, Pie Tin Filled with Styrofoam Peanuts, and Felt "Bat".
Procedure:
Tape one pie tin to the dome of the Van de Graaff generator and stack the rest of the pie tins inside the taped one. When you turn the Van de Graaff generator on the dome and the pie tins all have the same sign charge and thus repel. The same thing happens to the Styrofoam peanuts when placed on top of the dome.
Some other things to put on a VDG so that they fly off: tin pie plates, Rice Krispies in a cup, popcorn in a cup, cheerios. Hide popped popcorn in a Styrofoam cup, pour in un-popped popcorn, turn on VDG and watch the popped popcorn fly out.
Have the students hold Styrofoam peanuts in their closed hand and touch the VDG. Turn the VDG on and when they are charged have them open their hand and see the peanuts float away.
Styrofoam peanuts in a metal vs. Styrofoam cup. In the Styrofoam cup the peanuts will fly out, in the metal cup they will not due to a Faraday Cage effect. Our "metal cup" for this demo is a large copper mesh cup so that you can observe the action of the peanuts when the VDG is turned on.
A Halloween version of this is to place the felt "bat" on the top of the VDG. When the VDG is turned on, the bats head and wings will lift up, and he will appear to be looking at you before he flies away.
References:
- James G. Ellingson, "A Frankenstein Demonstration with the Van de Graaff Generator", TPT, Vol. 26, #7, Oct. 1988, p. 446.
- T. W. Haywood and R. C. Nelson, "Demonstration of Gauss' Law for a Metal Surface", TPT, Vol. 17, #9, Dec. 1979, p. 596, also A Potpourri of Physics Teaching Ideas - Electricity and Magnetism, p. 143.
- Borislaw Bilash II and David Maiullo, "Generating Electrostatic 'Phun'", A Demo a Day: A Year of Physics Demonstrations, p. 246.
- Ec-2: Freier and Anderson, A Demo Handbook for Physics.