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Homework Help: Dissipation Rate of a Propagating EM Wave

  1. Mar 19, 2012 #1

    I have a loop antenna I have been messing around with for a few years and I understand most of the physics behind it, especially with regards to Faraday's Law of Induction; however, I'm trying to work backwards now to determine a source voltage at a distance. For example, if a propagating EM wave comes in contact with my antenna in the horizontal creating 2 volts of induced charge while a lightning strike occurs, say, 20 km away in the vertical, how do I determine the lightning's voltage? Do I simply use 1/r^2 for linearity and 1/r^3 for point charge determinations or another equation? Also, what would be the proper unit notation - V/m or V/km or something completely different?

    Many Thanks,
    - uawildcat2008
  2. jcsd
  3. Mar 19, 2012 #2
    The voltage in your circuit is equal to the rate of change of magnetic flux through the circuit, the lightning can be modeled as an instantaneous electric dipole current, which creates a pulse of magnetic field. So what you can determine is the rate of change of the lightning current, if you know the surface area of your circuit and its orientation relative to the dipole current. I don't think you can determine anything else from your measurement.
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