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Circuit diagram of air?

  1. Jul 19, 2014 #1
    Hello, as just a fun curiosity, I was pondering what the circuit diagram of a square inch of air would look like. I figured I would ask the folks here what you think it would look like...

    I am thinking it would have a certain amount of capacitance, and maybe a very large zener with the breakdown voltage set at the ionizing voltage of air. What would it look like with variable caps or pots to account for pressure, temp, humidity?

    Your thoughts are most appreciated :)
  2. jcsd
  3. Jul 19, 2014 #2


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    A square inch? or do you mean a cubic inch between parallel plates that are 1" square ?
  4. Jul 19, 2014 #3
    Sorry, yes I meant cubic inch.
  5. Jul 19, 2014 #4


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    There would definitely by some capacitance associated with air. However, this also depends on the capacitor plates. Also, the breakdown voltage of air will depend a bit on the shape of the electrodes. I don't think that air acts as a zener either. Once an arc is established the voltage between the electrodes is much less than what it took to establish the arc.
  6. Jul 19, 2014 #5
    Also once an arc starts they tend to blow themselves out. Hot air rises and the ionized air tends to drift upwards and away.

    It's probably difficult to model air exaclty. From a circuit standpoint it will no doubt be extremely non-linear and high order.

    The kinds of questions your asking are probably of interest to companies that make high voltage breakers and other equipment for utility companies. If you dig deep enough there is probably a journal article somewhere for this topic.


    You might try looking into arc fault studies. This is a branch of engineering that estimates blast energies for various kinds of electrical failures. The general practice is to study a real service and determine how dangerous certain areas are so that maintenance workers are given the proper safety equipment to work in that area. At the end, an area is placed into one of 4 safety categories. A level 4 area requires that maintenance workers wear a full blast suit. The goal of this kind of engineering is to place equipment in a manner that reduces the number of level 4 areas and increases safety.

    I was never in the department that did this so I don't know too much about it but I bet that somewhere in their data are studies of how circuits behave when they arc.
    Last edited: Jul 19, 2014
  7. Jul 20, 2014 #6
    Thank you both very much!
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