The Van De Graff electro static generatorIn many physics and atomic experiments carried out today in the big labs there was found to be a need for good reliable high voltage static generator. Since world war 2 this need has been met by a device call the Van De Graff It main components consist of a metal dome ,an insulated top pulley ,to which a rubber belt revolves and on this belt is a metal comb which carries a charge to the metal dome.
A support collar insulated from the drive wheel and motor , most units I have seen are made from P.V.C.tubing Inside the collar a rubber belt is revolved at a reasonable speed by the drive motor in bigger units the belt may be enclosed in gas tight container for higher voltages.
As close as possible to the bottom of belt another metal comb is rested upon the belt. When the belt is rotated a charge is carried from the bottom plate to the dome via the top metal plate. After the belt is rotated for some time a charge will build up on the top dome ,care should be exercised when discharging, as a nasty shock could result.
Shown in illustration is simple machine which could be built from a tin can ,gum rubber band, and brass combs made from suitable brass sheets ,pvc piping and a suitable drive motor..
To see if a charge is building up on the tin can (dome) place a thread of cotton on top and if it levitates your machine has worked.
A good party trick is to fully insulate a party guest from the ground [preferably a female with long hair] and then get her to touch the dome, her hair should stand on end. Make sure you discharge unit before party guest makes contact with the ground again.
