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Homework Help: Negative lightning bolt

  1. Feb 4, 2004 #1
    Two questions.
    1. a negative lightning bolt delivers a 15C charge from the ground to the BASE of a thunder cloud (Vpd = 5.0GV)
    2. A positive lightning bolt delivers 20Ccharge from the Top of a thunder storm cloud to the ground (Vpd=30GV).

    Both questions ask how much work is done to move the charge during the lightning strike. The question does give a distance but does that matter. using W=qVab I get my answer but BUT is one answer negative and one positive and why?????????
    Thanks for the help in advance!!!
  2. jcsd
  3. Feb 5, 2004 #2


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    Science Advisor

    Re: Lightning

    The distance does not matter as long as you know the voltage. The units work themselves out if you include them (which you should ALWAYS do). As for whether it will be positive or negative, they should both be positive since it just says "how much work is done to move the charge". Your answers can only be negative if the question gives a referance point.

    I'll include the units in these so you'll see how they work out.
    E = Vq
    E = (5x10^9 J/C)(15 C)
    E = 7.5x10^10 J

    E = Vq
    E = (30x10^9 J/C)(20 C)
    E = 6x10^11 J

    See how nicely the units work out? 1V = 1J/C
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