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Homework Help: Capacitance and maximum charge HELP!

  1. Sep 9, 2008 #1
    As a crude model for lightning, consider the ground to be one plate of a parallel-plate capacitor and a cloud at an altitude of 620 m to be the other plate. Assume the surface area of the cloud to be the same as the area of a square that is 0.40 km on a side.
    (a) What is the capacitance of this capacitor?
    (b) How much charge can the cloud hold before the dielectric strength of the air is exceeded and a spark (lightning) results?

    I used C=E0 A/D (8.85*10^-12 C^2/N*m^2)(.16km^2/620m) and conversions also, but to no avail can someone please help
  2. jcsd
  3. Sep 10, 2008 #2


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    Hi seant,

    What number did you get as your final answer, in nF?
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