Question regarding Electrical Resistivity of metal vapors

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  • #1
andrew_bak
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What is the electrical resistivity of Caesium vapor? What is the electrical resistivity of Potassium vapor? Sorry there are no support material or reference links for this. Just a question. The unit must be in Ohm-meter.
 

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  • #2
phyzguy
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I believe a neutral gas is an electrical insulator, regardless of whether the atoms composing the gas are metals or non-metals. What would be the mechanism for electrical conduction?
 
  • #3
DaveE
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Presumably you mean a plasma? The gas must be ionized to conduct. In any case, you have left out sooooo many variables (hint: gas pressure is one). Maybe if you googled "Paschen's law" that would help. Except in the high current region (roughly, completely ionized) it is very non-linear.

It looked to me like there was a lot of information out there: "Cesium vapor discharge", for example. Here's one from the 1930's: https://nvlpubs.nist.gov/nistpubs/jres/21/jresv21n5p697_A1b.pdf
 
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  • #4
andrew_bak
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Presumably you mean a plasma? The gas must be ionized to conduct. In any case, you have left out sooooo many variables (hint: gas pressure is one). Maybe if you googled "Paschen's law" that would help. Except in the high current region (roughly, completely ionized) it is very non-linear.

It looked to me like there was a lot of information out there: "Cesium vapor discharge", for example. Here's one from the 1930's: https://nvlpubs.nist.gov/nistpubs/jres/21/jresv21n5p697_A1b.pdf
You are right. I should have been more specific. Let's assume that under the proper conditions (Pressure, ionizing radiation, etc..) we have conduction. What is the highest electrical conductivity ever recoded? for both potassium and casesium vapor?
 
  • #5
andrew_bak
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I believe a neutral gas is an electrical insulator, regardless of whether the atoms composing the gas are metals or non-metals. What would be the mechanism for electrical conduction?
Under the proper conditions (pressure, radiation) this metal vapor becomes electrically conductive.
 
  • #6
DaveE
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You are right. I should have been more specific. Let's assume that under the proper conditions (Pressure, ionizing radiation, etc..) we have conduction. What is the highest electrical conductivity ever recoded? for both potassium and casesium vapor?
Why would someone do that experiment? I don't think you'll find it.

Anyway, it is well known that you can have a negative resistance behavior in some gas discharge configurations. That is why fluorescent lights have ballasts, for example. I find the questions about negative conductivity confusing. What do you really want to know?
 
  • #7
andrew_bak
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Why would someone do that experiment? I don't think you'll find it.

Anyway, it is well known that you can have a negative resistance behavior in some gas discharge configurations. That is why fluorescent lights have ballasts, for example. I find the questions about negative conductivity confusing. What do you really want to know
Why would someone do that experiment? I don't think you'll find it.

Anyway, it is well known that you can have a negative resistance behavior in some gas discharge configurations. That is why fluorescent lights have ballasts, for example. I find the questions about negative conductivity confusing. What do you really want to know?
My question might be a bit confusing. I thought some one may have conducted this experiment out there. Considering that metal vapors are very light weight relative to solid copper wires: I thought why not design an electric motor where instead of rotor windings made of copper you have tubes filled with this metal vapor. By doing so, the rotor would be substantially lighter and thus the motor might rotate faster or less energy will be wasted. That's why I want to know the electrical conductivity of metal vapors at suitable conditions. I am fully aware that there are metals that are far lighter than copper (aluminum) but why not go even lighter? What conductive gases experience positive resistance behavior? Potassium or Caesium vapors don't experience that? Thank you for taking the time to answer...
 
  • #8
DaveE
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Solid copper will always be much more conductive than ionized gasses. Nearly all of the current in your motor windings will flow through the copper tube. This is assuming that you can keep the gas ionized inside the tube, which will be extremely difficult. Your motor will cost too much to make and perform poorly compared to "normal" designs.

"What conductive gases experience positive resistance behavior?" All of them. BTW, there aren't any conductive gasses, I think you mean plasma.
 
  • #9
andrew_bak
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Thank you for your response. It is very helpful.

Solid copper will always be much more conductive than ionized gasses. Nearly all of the current in your motor windings will flow through the copper tube. This is assuming that you can keep the gas ionized inside the tube, which will be extremely difficult. Your motor will cost too much to make and perform poorly compared to "normal" designs.

"What conductive gases experience positive resistance behavior?" All of them. BTW, there aren't any conductive gasses, I think you mean plasma.
I should have been more specific and called it plasma. You're right. When i said "tube" I meant that the tube would be made of material that is not electrically conductive. But considering the difficulty of keeping the gas in a conductive plasma state I can see the obstacles now. Thank you for your reply.
 
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