|MadSci Network: Physics|
Hi Ebere, You can find all kinds of good stuff about Van de Graaff generators at http://www.eskimo.com/~billb/emotor/vdg.html and it might be more helpful (certainly more thorough) than my answer. There are pictures and diagrams there too. There's also some information intended for teachers at http://hypertextbook.com/eworld/vdg.shtml and http://www.mvhs.fuhsd.org/~engtech/tech1997vandgf/genrator.htm which you might find interesting too. Electricity is carried around by extremely tiny particles which have "electric charge". All ordinary matter (like you and me, and the chair you're sitting on) is made up of protons, electrons, and neutrons, which are so small that you can't see them. The protons and electrons have electric charge, and the protons and neutrons stick together pretty strongly, but the electrons can sometimes move around fairly easily. By moving a bunch of electrons off of one object and onto another, we can build up extra electric charge in one place, and leave electric charge "missing" in the other. That's called "static electricity", and it's what a Van de Graaf generator does. There's a belt (often hidden from view) which rubs electrons off of the base and carries them up to the top, where a metal sphere collects them. The base usually picks up more electrons from whatever it's sitting on, so you don't notice the loss very much, but the metal sphere keeps collecting more and more electrons and pretty soon you can see all the interesting effects. Electrons can move around freely inside some materials (like metals) but are stuck wherever they land in other materials (like plastics and wood or cloth). The belt is usually made out of plastic or cloth, so when it picks up electrons they're stuck until they get up to the metal sphere, and escape onto the metal. Electrons repel each other, so once they get to the metal sphere, they all spread out evenly over the sphere. There are some really cool pictures at http://www.mos.org/sln/toe/toe.html and you can learn some more about electricity at http://www.toronto-montessori.on.ca/bsutherland/electricity/ fundamentals.html and http://www.ed.uiuc.edu/coe/SNN/Jan-Feb.96/shock.html and http://www.waterw.com/~science/january.html -Steve Levin __________________________________________________________ DISCLAIMER: Just because I work for JPL/NASA/Caltech doesn't mean anything I say is in any way official. This is just me talking, not NASA, JPL, or Caltech.
Try the links in the MadSci Library for more information on Physics.