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Re: Positive vs Negative Van de Graaff Polarity

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  • Antonio
    ... Long sparks only occur if the ionization of the air starts at the positive end of the spark. With a negative terminal the breakdown occurs at your hand
    Message 1 of 4 , Jun 7, 2010
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      --- In VanDeGraaffGenerator@yahoogroups.com, "juke_family" <juke_family@...> wrote:
      >
      > I made an attempt to reverse the polarity of my small Science First generator. I put Al foil on the bottom Teflon roller and Teflon tape over the top Al roller. It seemed to work, but I noticed that the sparks were less frequent and more painful in the negative mode. Is this typical?
      >
      Long sparks only occur if the ionization of the air starts at the positive end of the spark. With a negative terminal the breakdown occurs at your hand when you move it close enough from the terminal and the resulting spark is long and powerful.
      With a positive terminal you get only corona before the distance is of only a few cm.
      Long sparks are less frequent because it takes more time to accumulate enough charge and voltage.

      Antonio Carlos M. de Queiroz
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