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Homework Help: Find energy of a lightning strike

  1. Mar 5, 2014 #1
    Consider the Earth and the cloud layer 800 meters above the earth to be the place of a parallel-plate capacitor. The cloud layer has an area of one kilometer squared. Assume this capacitor discharge that is lightning occurs, when the electric field strength between the plates reaches 3.0X10^6 V/m. What is the energy released if the capacitor discharge completely during a lightning strike?

    C=(€*A)/d=((8.85*10^-12)(1*10^6m))/800=1.11*10^-8 F
    Energy density=(0.5)(€)(E^2)=(.5)(8.85*10^-12)(3*10^6)^2=39.83=energy/volume therefore energy=39.83*(A*800)=3.19*10^10 J

    Is this correctly done? Any help is appreciated.
  2. jcsd
  3. Mar 5, 2014 #2
    Yes, that looks right. It's a bit indirect to go through energy density though -- you could solve it a bit more directly with [itex]U = \frac{1}{2}CV^{2}[/itex]. Either is fine though, of course.
  4. Mar 5, 2014 #3
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