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Homework Help: Estimate the Dielectric Breakdown of Air

  1. May 30, 2015 #1
    1. The problem statement, all variables and given/known data
    A capacitor is charged to V = 5 kV.

    A wire is then connected to one plate and is slowly connected to the other. Before actually touching the plate, a spark of length l = 1 cm shoots from the wire to the plate. Using this information, estimate the dielectric breakdown of air, which is the electric field Eair required to generate a spark in air.

    2. Relevant equations
    [tex] E = \frac{V}{d} [/tex]

    3. The attempt at a solution
    [tex] E = \frac{V}{d} = 5 * 10^5 \frac{V}{m}[/tex]
  2. jcsd
  3. May 31, 2015 #2

    rude man

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    Homework Helper
    Gold Member

    This is about as good an estimate as you can get.
    However, realize that the E field is not constant between the wire and the plate. In fact, the E field at a point like the end of your wire will be very much larger than V/h, so breakdown most probably occurs at and near the wire's tip.

    But your estimate is as good as anyone else's, under the circumstances.
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