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Static charge

  1. Mar 22, 2010 #1
    i been watching some lectures from OCW and the professor said something like a ball with a radius of 1m can not exceed 3MV because of the electric breakdown of air.

    to me it sounds like you can not exceed a potential difference 3MV per meter. so it does not matter the physical size of an object just the voltage difference over a distance is less.
  2. jcsd
  3. Mar 22, 2010 #2

    Andrew Mason

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    It is the strength of the electric field, not the potential of the ball that determines when the air breaks down.

    You can use Gauss' law to determine the electric field:

    [tex]\int E\cdot dA = \frac{q}{\epsilon_0}[/tex]

    [tex]E = \frac{q}{4\pi r^2\epsilon_0}[/tex]

    The electric potential outside the sphere is the same as if you were dealing with a point charge:

    [tex]V = \frac{q}{4\pi r\epsilon_0}[/tex]

    which means that E = V/r

    So you can see that for a given voltage of a conducting sphere, the field strength varies as 1/r.

  4. Mar 22, 2010 #3
