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Measuring the conductance of flames

  1. Aug 22, 2005 #1
    Hi, I'm doing a project on mesuring the conductance of flames, but I need a lot more physics to back up my theory. I'm pretty sure that the boltzmann factor is involved, however I can't link the two items together.

    The experiment so far has worked, by using a bunsen burner to burn the salts of elements, i.e. Barium Chloride, Calcium Chloride etc and measuring the conductance of the flame across a gap of 2mm between 2 nichrome electrodes.

    Thanks in advance for any replies! :bugeye:
  2. jcsd
  3. Aug 22, 2005 #2

    Chi Meson

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    Do you mean electrical conductance or thermal conductance? If you are talking about electrical conductance ("conductivity"), as I think you are, your mention of the Boltzman constant indicates that you are up the wrong tree.

    Your experiment indicates a rather interesting idea and I urge you to continue. To obtain meaningful data you will need: a multimeter that measures voltage, current and resistance; a variable voltage source (0 to 12 V DC would be good); a physics texbook with four or five chapters on electricity and circuits.

    Do not mess with voltages higher than 12 volts, and keep your skin dry. Watch "Leathal Weapon 2" to see why.
  4. Aug 23, 2005 #3
    Thanks for the reply,

    I have already conducted the experiment with reasonable success, but what I really need is some physics to relate the reason behind the following results:

    Sodium 1.23
    Calcium 1.37
    Strontium 1.50
    Potassium 2.18
    Barium 1.66

    (values are measured in Conductance (µS))

    What I really need to know is the physics behind what makes this work, and why the conductance increases with the number of electrons in the atoms shells. Is there any formula/theories which relate to this?
  5. Aug 25, 2005 #4


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    I can't give you any patent answers, but think you will have to consider the ionization state of the various chemials. Perhaps the larger molecules have a tendency to higher states of ionization??

    Many years ago I read of something called a Flame speaker. To make one all you would need do is place an audio signal on your needles. The audio signal will cause oscilations in the flame which will act a nearly perfect speaker. Have always wanted to try it.
  6. Aug 25, 2005 #5


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    Are you expecting conductivity to go like
    exp(-ionization energy/k_B*T)

    I'd suggest you first make sure you're burning materials at the same rate.
    then try plotting on log scale "might" get a straight line.
    (but don't forget the Cl that's also in the salt!) - Good Luck -
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