Theoretical Maximum Positive Voltage

Discussion in 'Physics' started by Wendy, May 16, 2011.

  1. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    The OP had some trouble posting this, so I did it for him...

    http://forum.allaboutcircuits.com/showthread.php?t=54563

     
  2. #12

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    Nov 30, 2010
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    Expanding on the question...

    In Ph readings, the definition of Ph is about ratios. There is a limit. In electron theory, voltage is about concentration of electrons at one place compared to concentration of electrons at some other place. If I call Earth one of the places where electrons exist and a theoretical sphere in a theoretical non-leaky place another place that electrons can be, you can add all the electrons you like to the sphere and achieve all the negative voltage you want, I think. When it comes to removing electrons to achieve a positive voltage, is there a limit, and what would the limit be?

    This has no practical application. It is just a curiosity thing.
     
  3. Wendy

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    If you are sucking electrons out then I think the maximum is pretty clear cut, though I don't have any way to calculate it. Most of the electrons are bound chemically in the matrix, all you are removing are the floaters that are a characteristic of metals. These floaters can move from atom to atom freely, and are not tightly bound. They do make the metal electrically neutral however.

    To really get a large number of electrons to move you need to ionize the material, which is to say make it a plasma. That sounds like it is out of bounds of the thought experiment.

    The other side of this experiment is how many electrons can you pump in. Without knowing I think the numbers could be larger on that side.
     
  4. #12

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    I think it comes down to, "what is the concentration of electrons on Earth?" I feel sure that there are spare electrons (floaters) laying around all over this place. If there was a place with no "floaters", what voltage would be measured between there and earth ground?
     
  5. magnet18

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    If you assume you have a one gram pure sphere of hydrogen atoms, one proton and one electron, then you could pull 6.02x10^23 electrons off of it. That is 96440.4 coulombs of charge. Each electron has a principal quantum number of 1, meaning they each have 2.178x10^-18 joules of energy, following E=2.178x10^-18/n^2 J. Multiply by 6.02x10^23 to get a total of 1311156 joules of energy. Volts equals joules per coulomb, which is 13.6V, assuming the reference point is neutral (one electron per proton)
    If someone thinks I'm wrong please speak up, I might be using incompatible equations.
     
  6. BillO

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    Why would there be? What are you thinking here?
     
  7. Wendy

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    Goes back to plasma case. You aren't going to get much off a cool gas, and hydrogen in its gas state is not a conductor. Goes back to the limits I mentioned on the other thread.

    Theoretically there is a metallic state of hydrogen. No one has ever seen it though.
     
  8. magnet18

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    He's thinking that eventually you can no longer remove electrons, I've had the same thought in the past.

    Since we were all being theoretical, I was using the simplest element. I could have said 16 grams of oxygen, or 14 grams of carbon, but they have multiple orbitals and multiple quantum numbers and blah blah excessive numbers.

    Feel free to calculate the maximum voltage of aluminum using the method I just did, if you feel ambitious, it has 2 electrons of quantum number 1, 8 of quantum number 2, and 3 of quantum number 3, and a molar mass of 26.8 grams per mole.
    And technically, if you pull this many electrons off the atoms will probably either fuse or explode outward or something, but I bet it wont stay normal.

    Also, keep in mind that one gram of aluminum is going to be a really small amount.
    Like, super small. 27 grams of it is about the size of a .223 round.
     
    Last edited: May 16, 2011
  9. Wendy

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    Thing is, you are assuming you can suck every electron out. As I said in post #3, this is flat out impossible. Most of the electrons are bound down, hard, locked in the matrix of the metallic solid. Only the floaters are up for grabs, and that is only the outer shell of the atom. This goes to why metals are conductive. In insulators all the electrons are bound, which is why you can deposit them on the surface in the form of static electricity. The free electrons have no where to go.
     
  10. #12

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    I was thinkng more like if you had an imaginary perfect AC generator and diode and grounded one side of your circuit to earth, what is the maximum positive voltage that could be achieved, given that the Earth is where you place one probe of the imaginary perfect voltmeter. None of this stuff about plasma or how many grams of a element will create a higher voltage makes any sense to me.
     
  11. Wendy

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    The reason how many grams is important is it is tied to the number of electrons in the material, both the free and bound. While I can't work out the math easily, I understand the concepts. The more mass, the more electrons you can move about, and the greater the voltage stored.

    You do realize you are talking about the positive side of a capacitor?
     
  12. #12

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    Yes, a capacitor model works as well for me as pretending our moon was free of electrons which are not part of a molecule (where the electron is paired with a proton) and we could stick a voltmeter probe in it.
     
  13. Wendy

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    As with a capacitor, by itself it has no voltage. It has to be compared with something else. If the two points are at the same potential there is no voltage.
     
  14. #12

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    Well, for the moment, pretend a cloud of protons drifted by our moon and all the free electrons were turned into hydrogen atoms by magic fairy dust. Then stick a voltmeter probe in the moon and another in Texas. What's the voltage?

    Ps, Turning our moon into a plasma is not allowed.

    I think I have defined the question rather well. I also think nobody knows the answer, but there are a lot of people with more education than I. I was hoping maybe someone had done a brilliant experiment like "finding the charge of a single electron" and found out how many free electrons are in an average cubic centimeter of Texas, or Rhode Island, or Paris, France.

    I will watch this thread and hope someone wanders by with more information. Thank you all, so far.
     
  15. magnet18

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    The charge of a single electron is 1.60217646 × 10^-19 coulombs.

    Voltage is joules per coulomb, and is also known as electromotive force, or electrical pressure.

    Electrons have no specific energy, it depends on what their doing, and as I said, in an atom, that is determined by the quantum number, or orbital level, or how close it is to the nucleus.

    When you turn it to a plasma I'm not sure how to calculate it.
     
  16. Wendy

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    It's actually easier than that. Pick metal. Look up it's valence number, this is the number of electrons that are mobile. Weigh the metal, calculate the number of atoms in that sample. Multiply the number of atoms vs the valence number.
     
  17. #12

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    From the answers I'm getting, it seems that rectifying a positive voltage from a sine wave strips the electrons off molecules, leaving proton-neutron groups without their electrons. I didn't know that happened. I thought I was talking about free electrons...ones that don't have a nucleus and/or a proton to orbit.

    Does this mean that enough positive voltage naturally turns everything into a plasma? Nucluei wandering around without their electrons?
     
  18. Wendy

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    No, but a plasma is ionized. Ionization is the stripping of electrons from their atoms, and plasmas are considered a fourth state of matter. No matter what element is ionized, the ionized gas is always conductive, usually hot, usually glowing. A camp fire is a natural plasma.
     
  19. magnet18

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    Yes, but when you ionize it you might be pulling more than the valence number off, like when you ionize helium, it's valence number is zero.
     
  20. magnet18

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    Just to clarify, fire isn't plasma, it's an exothermic reaction resulting in the excitation of electrons and release of photons. Trust me, it's not conductive. I've tried.

    Neon tubes, fluorescent lights, and lightning, however, are all common plasmas.
     
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