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Electric charge vs. altitude - what energy is required?

  1. Jun 5, 2012 #1


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    Hard to find a suitable title, but I have a simple question about electric charce and how a generator is affected by how high up one of the charged plates are:

    If I want to charge two plates with +/- 100kV, then electrons are forced from one plate to the other, so one plate is positive, and the other plate is negative. The negative plate must become heavier, and the positive plate must be lighter. The charging itself will take energy.

    The first stupid question here is, will it also require energy to move the electrons upwards if the becoming negative charged plate is high up in the air while the becoming positive plate is on the ground?

    The second stupid question is, if the plates is discharged, will the discharge cause the electrons not only flow back to the positive plate, but also that gravity will cause the positive plate to be slightly negative when the discharge is finished?

    See attached drawing with my thoughts written into it.

    Attached Files:

  2. jcsd
  3. Jun 5, 2012 #2
    I don't think you need to worry about gravity in your "generator". In any measurement there is going to be a margin of error. The difference in energy from gravity versus the difference in energy from electrical charge will be so small that it will get lost in any real world measurement. If necessary I am sure that you cold calculate the amount of energy it takes to lift an electron to that height, but since that energy would be swamped by the electrical energy I don't see why you would want to try to measure it.
  4. Jun 5, 2012 #3


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    I am just thinking experimentally - in principle. One electron weight 9.11 x 10^-28 grams, but there is quit many electrons that has to move from one place to another.
    For example, how many more electrons must a negative pole have compared to the positive pole to measure 1V? Then it should be possible to calculate the "weight of 1V"(?).

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