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Making current with van de graff gen.

  1. Dec 21, 2003 #1
    Couldn't I create a current in a circuit using a van de graff as the source of voltage? Many thanks.
     
  2. jcsd
  3. Dec 22, 2003 #2

    russ_watters

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    Staff: Mentor

    Yes, but at very low current.
     
  4. Dec 22, 2003 #3
    Re: Re: making current with van de graff gen.


    Why is that? Isn't a wire a veritable sea of free electrons?
     
  5. Dec 26, 2003 #4
    re: van de graph generator

    The van de graph generator itself by nature produces a large quantity of voltage, however the current produced is extreamly small. Ultimately, you would need to feed the aquired power from the v.d.g. through a step down transformer in order to lower the voltage and raise the current. What method of aquiring are you using (thinking about using)?

    There's too much natural resistance in wire to permit free electron motion without constant influential drive.
     
  6. Jan 7, 2004 #5
    Re: Re: Re: making current with van de graff gen.

    The wire isn't the problem.

    Inside the VDG there are charges sprayed onto the rubber belt, and the maximum charge per area is limited. (Put too much charge on the belt surface, and a spark will let it flow back off again.)

    The speed of the belt is also limited. If you run the motor too fast, the belt starts flapping back and forth.

    For little desktop VDG machines, the most you can get out of them is 20 or 50 microamps. But don't forget, at a voltage of 100,000V that gives you a few watts.

    The professionals attain higher currents by running the belt in a vacuum chamber where no sparks are allowed, so the max charge on the belt can be much higher. But to force charge onto the belt, the belt must have conductive patches. The solution is to use a sort of metal chain thingy in place of a rubber belt. Such a device isn't called a VandeGraaff machine. Instead it's called a "pelletron"
     
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