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Electric field frequency at room temperature

  1. Jul 10, 2012 #1
    Hello, I am trying to figure out what frequency emf there might be at STP. I mean that like this - Imagine that I have a nano-sized voltmeter with one probe grounded, and it's small/sensitive enough so that as air molecules collide with the other probe, it picks up a voltage. What sort of frequency would that change at? Is there a way to solve for this, or a ball-park figure?

    thanks.
     
  2. jcsd
  3. Jul 10, 2012 #2

    CWatters

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    "air molecules"? You mean Oxygen and Nitrogen molecules. Are they charged?
     
  4. Jul 10, 2012 #3
    yes oxygen and nitrogen molecules, and maybe some Co2 and water vapor too. not necessarily charged. maybe a small portion of them. Like the air in my room, nothing special. I'm sure some of the molecules have dipole moments.
     
  5. Jul 10, 2012 #4

    CWatters

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    Spectral line for oxygen is about 513nm. So frequency about 5.85*10^14 hertz ?
     
  6. Jul 10, 2012 #5

    Bobbywhy

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    The spectrum of oxygen undergoing electrical discharge excitation contains at least seventy-three (73) separate emission lines between four thousand (4,000) and seven thousand (7,000) Angstroms.

    http://astro.u-strasbg.fr/~koppen/discharge/

    If we select only one of those emission lines and take it’s inverse to convert from wavelength to frequency (as above) the result could not be measured by any voltmeter, and seems meaningless.

    It appears the OP by elegysix is not easily answered, because measuring individual dipoles of gas molecules is probably impossible.
     
    Last edited: Jul 10, 2012
  7. Jul 10, 2012 #6
    I think I remember something in thermo or chemistry about it, like the average rate of collisions between gas molecules. Would that give me a ball park figure? Anyone know what that might be called?
     
  8. Jul 10, 2012 #7
    Some molecules may have dipole moment.
    Oxygen, nitrogen and CO2 don't have permanent (electric) dipole moment.
    Water is the only molecule in the above list with a permanent dipole.
    What do you actually want to measure or to do?
     
  9. Jul 11, 2012 #8

    Drakkith

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    I don't believe your probe would pick up a voltage from neutral particles colliding with it.
     
  10. Jul 12, 2012 #9
    here is the idea... haven't worked out any numbers yet, so it's just a thought experiment for now. There are two set ups for this thought experiment.

    1) take a capacitor (very high C) and bias it in a specific way. have the capacitor placed inside a faraday cage or conductor so there is little or no external E field acting on the system. Connect a lead to one side of the capacitor and let a very small point of the lead be in contact with the air and fields outside the cage. The purpose is to try and have AC current flowing in the wire, even if it is absolutely minuscule.

    2) attach many wires to a conductive plate, letting the other ends be seperate and unconncected. have that system placed inside a conductor/faraday cage. Only allow the very tips of the unconnected ends to be exposed to the air and fields outside the cage. This way, a small difference in potential between any tips of the wires might cause a very small AC current in the wires and connecting plate.

    The purpose is then to wind toroid coils around the wires carrying the small AC current, in hopes to remove some energy from the gases. I expect that this will take many, many hundreds or thousands of wires or coils to produce any significant power, if it is at all possible.
     
    Last edited: Jul 12, 2012
  11. Jul 12, 2012 #10

    ZapperZ

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    I have a feeling the OP, and many people who responded to this thread, are all talking about different things, and none of them sinking in.

    elegysix: before you invent a device here, can you tell me why you think that a neutral molecule will produce an EM field or a potential by itself? Let's established clearly what the physics involved here first and try to understand the scenario.

    Zz.
     
  12. Jul 12, 2012 #11

    Bobbywhy

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    elegysix, Thank you for finally, after all the above obfuscation, making clear your proposal!
    In my estimation no significant electrical power could be gleaned from such an apparatus.
     
  13. Jul 14, 2012 #12
    I don't really expect a neutral molecule have much effect on this, if any at all. Hopefully it will, but I too doubt it.

    I expect that water vapor molecules or others with a significant dipole will be able to cause an effect, as well as any unbalanced molecules in the area.

    I may have a Static E field in the vicinity to attract any unbalanced molecules in the area, to increase the effect. (I may try this)

    The idea is that maybe with this, I can turn some of a gases' kinetic energy (heat) into electrical power.

    I realize that this is going to be a very small amount of work.

    However, there are no moving parts involved, and I can "theoretically" build millions or more of these conductors, which would then draw enough power to be significant. I don't imagine that there would be much cost to keep such a thing operating, it is essentially only wires, and there is no significant power through any one wire. Make the world cooler by gaining electric power, with almost no upkeep - it's worth at least trying to me.
     
  14. Jul 14, 2012 #13
    I think this violates the laws of thermodynamics, in moving heat from a hot object and giving it to a cold object, for example, if you were to use this device to power a heater in another room.
     
  15. Jul 14, 2012 #14
    The KE of a gas molecule is approximately equal to 3/2 kT. When you know its mass and the space it occupies you can work out a ballpark frequency.

    But as you state, to farm any meaning full amount of energy say from a gas heated by (eg) solar energy you will need millions or more conductors. The frequency of the many small generated currents will all be out of phase and hence will cancel. Therefore you will need to rectify each small ac current into a dc flow. This means for each conductor you will also need a small semiconductor. And this way you are close to the idea of a solar panel.

    Full marks for the idea but you’ve been beaten to it a long time ago. Anyway I hope you keep on going, we need people like you.
     
  16. Jul 14, 2012 #15
    I don't think it violates them, it isn't violating conservation of energy either. Rather, the moving molecules with an electric field should induce a small AC current in the conductor, essentially slowing down the molecules while providing a current. It is just transforming energy. Like the opposite of a fan.
     
  17. Jul 14, 2012 #16
    Who/what was made like this before? I think this is somewhat different from a solar panel. Did someone else already try this?

    thanks
     
  18. Jul 14, 2012 #17
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