Is the temperture of one atom directly equal to its speed?

[Beamin]

Or is temperature only an average that can only happen when particles interact through crashing into each other, needing at least two to interact?


If not what is the temperature of an alpha particle or a thermal neutron? Does it's mass play a role since an alpha can disturb more particles?
Or an electron as it passes down a wire? It must be the amps that produces the temp since amps are a measure of actual energy rather then voltage potential energy.

But since absolute zero means you have to take away zero point energy and stop it from vibrating is the temperature the measure of the vibration of it if  it was interacting with of other atoms particles? Or am I confusing temp with pressure in pv=nrt?

These things keep me up at night.

[coppercone2]

a single atom has kinetic energy. the more particles in a system the better use the word temperature will have.

temperature is related directly to average kinetic energy. anything average is big as to put weird interactions under the noise floor so a statistical equation relating to kinetics works.

maybe you can argue the sub components of an atom can have some kind of 'temperature' but their interaction is clearly different.

I would argue that you need a meaningful phonon to use the word temperature.
https://en.wikipedia.org/wiki/Phonon

at first it seems like you need to put a lower mass limit on temperature  to clarify its use as a word but perhaps you can do something with phonons and impedance but this is very far out to me at this point in time

[T3sl4co1l]

Yes and no.  Temperature is a thermodynamic, bulk property, so it's at least disingenuous to speak of temperature of a lone particle.  The connection between temperature and particle energy comes from statistical mechanics, which finds E = k_B*T, so it's not completely unfair!

Absolute zero doesn't mean "take away zero point energy", which is impossible of course -- the energy at zero is the energy at zero, that's how it's defined.

Motion doesn't need to stop, just the exchange of it with surroundings.  The lowest energy state of a system can still have multiple ("degenerate") states with equal energy levels.  Particles can exchange energy with each other, as long as the net change is zero.

Example: liquid helium doesn't actually freeze, it remains a superfluid (though it does freeze under pressure).  A superfluid does not dissipate energy as viscous shear or turbulence, it conserves it (apparently as quantum vortices).

Superconductors retain current flow, at zero voltage drop mind, and therefore retain a magnetic field too.  Which is fine, because a magnetic field isn't an exchange of energy either, magnetic field is conservative.  Or capacitors which remain charged, assuming zero leakage.  Electric field is conservative, too.

As for the examples, energy corresponds to temperature, so an alpha particle at a few MeV isn't going very fast (due to its large mass), as particles go, but it is at quite a high equivalent temperature!  Electron velocity in conductors is much higher due to thermal energy (~10^5 m/s) than to drift velocity (~cm/s), even at high current densities.

Velocity saturation can occur in some materials, where the electron density is small -- semiconductors -- and the breakdown E-field (impact ionization threshold) is high.  GaAs is such a material.  Entering this regime causes negative resistance (current decreases as voltage rises).  This acts essentially as fast as the electric field itself getting into the material -- an easy way to generate microwaves (10s of GHz) with a small hunk of homogeneous material!  Although, despite being homogeneous, they are called "diodes", when they'd really be monodes... of a sort.  Gunn diodes to be exact.

Again, amps or volts aren't a measure of energy, their product with time is (E = V*I*t).  You can have voltage without current, or vice versa, and consume no energy (or, slosh energy back and forth in a resonant circuit*).

*Even superconducting resonators have nonzero losses, actually.  Pretty good, with a Q factor up to 10^8 or thereabouts -- better than quartz crystals -- but still a time constant on the order of seconds, definitely not everlasting.

Tim

[bsudbrink]

<iframe width="674" height="515" src="https://www.youtube.com/embed/eZdUKMDfJ_o" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Ya know, I see lots of other posts with embedded youtube links but I can't figure out how to do it.

[Cerebus]

<iframe width="674" height="515" src="https://www.youtube.com/embed/eZdUKMDfJ_o" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Ya know, I see lots of other posts with embedded youtube links but I can't figure out how to do it.

Just put the link, just as you would any other, and the forum system automagically does the embedding.

[bsudbrink]

I pasted in the embedable link (YouTube, copy embed code) and you see the result above.  I guess I'm not holding my mouth right.  I'm using Firefox if that makes a difference.

Anyway, the above link is to the Temperature episode of Cal Tech's Mechanical Universe.  The best videos on basic physics that are available.

[Cerebus]

I pasted in the embedable link (YouTube, copy embed code) and you see the result above.  I guess I'm not holding my mouth right.  I'm using Firefox if that makes a difference.

Anyway, the above link is to the Temperature episode of Cal Tech's Mechanical Universe.  The best videos on basic physics that are available.

Don't put the embed code, just the basic URL for the video, with no "feature=" or anything like that, in a pair of  [ URL ] [ /URL ] tags like this:

[ URL ] <URL Mangled so the magic doesn't happen> < damn it still does happen> [ /URL ]

but without the extraneous spaces (that I put in so you would see the tags).

See, no matter how hard I try SMF is recognising the You Tube URL and doing its magic. Let me try that again:

[ URL ] h t t p : / / w w w . y o u t u b e . c o m / w a t c h ? v = e Z d U K M D f J _ o  [ /URL ]

Yeash! That was hard work getting it to NOT display the video. Hopefully now you get the gist.

[bsudbrink]

[bsudbrink]

Eureka!

[coppercone2]

i wanna make a flip book featuring that guy since I see his face so many times now

[Cerebus]

i wanna make a flip book featuring that guy since I see his face so many times now

Sigh. Only you would fail to recognise Sir Isaac Newton and label him "that guy"...

[coppercone2]

honestly I thought it was boyle

[Beamin]

Often in astronomy they talk about gas with temperatures of 2.7k but the gas is tens of H atoms per sq. meter so they aren't going to interact I don't think. If they did they would form H2. Maybe they are talking about the speed of the particles and extrapolating a temp and this is just dumbed down?


So does an ionized molecule have a higher temp then a non ionized since the electrons are in a higher energy state and they translate to a temp? When you have "cold" plasma in a CFL that means 99.99% of the atoms are not ionized but that 0.01 are and at very high temps (actually isn't this how all hot things are become hot: just a few atoms are very hot, hence how they made negative temps with the inverted sombrero hat temp curve in some lab) and you only need a few to give off light? As far as I know plasmas don't exist at cool temps.


Another thing when they say "cold plasma" do they mean just the outer or valance band is missing electrons and that makes it reactive/charged? Most processes/chemical reactions only deal with the outer electrons. This would make things technically radioactive maybe? I saw that a Li Hydrogen Fluorine rocket engine exhaust messed with the electronics due to all the free radicals it puts out. I always thought chemical states like OH- groups didn't do this even in air instead of a ionic solution. Candle flames don't mess with radio and they have OH and CH4+ groups and a lot of reactions between CH2 +O2->CO2 H2O.


On a related note to temp and semiconductors I watched a video (trying to find link) where this Lispy british guy does an excellent job explaining how they work due to IR photons causing effects in with the doping agents conduction band vs valance band and how the conduction band doesn't conduct but the valance band does. This should be why high temp super conductors work and why metals conduct better as they cool. Something to do with the photons providing the kick of energy to get things to work. It uses the 4 state of silicon and supplies electrons and holes with 3 or 5 valance electron atoms like phosphorous +5(+1) or boron +3(-1).

[IanB]

just the basic URL for the video, with no "feature=" or anything like that, in a pair of  [ URL ] [ /URL ] tags

Don't even put the URL tags. Just paste the plain URL from the YouTube share link, like this:

Code: [Select]

https://youtu.be/eZdUKMDfJ_o

[coppercone2]

well you can relate the plasma light to its electrical power consumption which gives you an idea of how its averaged out, looking at the power loss in the system

[IanB]

Often in astronomy they talk about gas with temperatures of 2.7k but the gas is tens of H atoms per sq. meter so they aren't going to interact I don't think. If they did they would form H2. Maybe they are talking about the speed of the particles and extrapolating a temp and this is just dumbed down?

It's not about interacting (as in bumping against each other), it's a question of scale. If you look at a cubic lightyear of space, you can measure the temperature of the radiation it is emitting (or equivalently, the temperature of a hypothetical black body it is in equilibrium with). That temperature would be 2.7 K.

(By the way, take care about your units. "K" uppercase is kelvin, "k" lowercase is kilo-.)

(And by the by the way, "H atoms" don't exist individually. They form H₂ molecules where two hydrogen atoms are joined together.)

[coppercone2]

also with plasma I think you get a higher netural gas temperature but cooler electron temperature (or is it ion) temperature when you increase the density of the plasma, that is if you increase the gas pressure you need more energy to get the same emission out of it?

if you had a plasma tube that had some kind of piston in it to compress it hooked up to a constant energy - power supply and then it was compressed would there be a decrease in light output unless you put more energy into it? or would that effect the impedance due to geometry of the piston so you can just add more gas and let it cool down, or can some kind of weird latching happen if you add gas to a plasma where it wont be the same if you reionize it at increased density? i dont think so

[Cerebus]

honestly I thought it was boyle

To be fair, they all look the same in those periwigs.

[Beamin]

Had to use the -> key a lot and was kind of a 5th grade level. Why do they say R= 2/3 it's more like 0.06 that's almost 10X different. Is that for 'F which would make pv=nRT a nightmare to use. They forgot to mention that pv=nrt breaks down since gas molecules have size and are not point particles.

[IanB]

Had to use the -> key a lot and was kind of a 5th grade level.

OK... 

Why do they say R= 2/3 it's more like 0.06 that's almost 10X different.

Because maybe it's not 5th grade level? (Hint: they didn't say R = 2/3. Also, R has units of measure. You cannot say "R = 0.06" without saying what units you are using. What are the units of 0.06 when you say that?)

[Brumby]

See, no matter how hard I try SMF is recognising the You Tube URL and doing its magic. Let me try that again:

[ URL ] h t t p : / / w w w . y o u t u b e . c o m / w a t c h ? v = e Z d U K M D f J _ o  [ /URL ]

Yeash! That was hard work getting it to NOT display the video. Hopefully now you get the gist.

Doesn't have to be.  Here's how I do that sort of thing:

https://www.youtube.com/watch?v=eZdUKMDfJ_o

Just "quote" my post to see how I did that.

[T3sl4co1l]

Often in astronomy they talk about gas with temperatures of 2.7k but the gas is tens of H atoms per sq. meter so they aren't going to interact I don't think. If they did they would form H2. Maybe they are talking about the speed of the particles and extrapolating a temp and this is just dumbed down?

If it was that cold, it would be H2, yes.

Much of the universe is not at 2.7K, however.  The CMB is at 2.7K, and it's photons not protons.  Solar wind is in the low keV, where it will stay ionized until it cools (and, I guess it doesn't cool very quickly on account of the low density).

Further reading:
https://www.ethz.ch/content/dam/ethz/special-interest/phys/particle-physics/star-n-planet-formation-dam/documents/Courses/Astrophysics%20III/A3C4ism.pdf

So does an ionized molecule have a higher temp then a non ionized since the electrons are in a higher energy state and they translate to a temp?

At the very least, 13.6eV is given up on recombination, and a few more eV on molecular formation; as long as the temperature is above there (~10^5 K), there will be a large fraction of ionized hydrogen.

Cooling rate is probably pretty rapid around there, because the milieu of ionization and recombination means lots of light emission.  There's not much recombination at high temperatures (~keV), particles just bounce off each other without ever reaching a bound state.  (Very hot plasma -- in the 100keV range -- will be opaque and emissive again because of pair production and 511keV gamma rays.)

When you have "cold" plasma in a CFL that means 99.99% of the atoms are not ionized but that 0.01 are and at very high temps (actually isn't this how all hot things are become hot: just a few atoms are very hot, hence how they made negative temps with the inverted sombrero hat temp curve in some lab) and you only need a few to give off light? As far as I know plasmas don't exist at cool temps.

The ionized fraction is at the top of the thermal spectrum, the outliers.  It's not very meaningful to say they're "hotter"; that's true by definition, like saying people 6'6" in height are taller than the rest.

Probably the temperature distribution is very nonequilibrium near the electrodes, where cold gas in contact with the surface gets impacted by electrons and ions, adding a high temperature fraction.  Idunno, plasma is complicated stuff and I don't know too much about it.

Another thing when they say "cold plasma" do they mean just the outer or valance band is missing electrons and that makes it reactive/charged? Most processes/chemical reactions only deal with the outer electrons.

Yes, I think that's what they mean: a large fraction of unionized gas.  Or, actually, more generally, molecular gas probably?

This would make things technically radioactive maybe? I saw that a Li Hydrogen Fluorine rocket engine exhaust messed with the electronics due to all the free radicals it puts out. I always thought chemical states like OH- groups didn't do this even in air instead of a ionic solution. Candle flames don't mess with radio and they have OH and CH4+ groups and a lot of reactions between CH2 +O2->CO2 H2O.

Radioactivity is nuclear, N/A here.

Tim

[IanB]

They forgot to mention that pv=nrt breaks down since gas molecules have size and are not point particles.

I think they did mention that. Did you miss it?

[Beamin]

Often in astronomy they talk about gas with temperatures of 2.7k but the gas is tens of H atoms per sq. meter so they aren't going to interact I don't think. If they did they would form H2. Maybe they are talking about the speed of the particles and extrapolating a temp and this is just dumbed down?

It's not about interacting (as in bumping against each other), it's a question of scale. If you look at a cubic lightyear of space, you can measure the temperature of the radiation it is emitting (or equivalently, the temperature of a hypothetical black body it is in equilibrium with). That temperature would be 2.7 K.

(By the way, take care about your units. "K" uppercase is kelvin, "k" lowercase is kilo-.)

(And by the by the way, "H atoms" don't exist individually. They form H₂ molecules where two hydrogen atoms are joined together.)

[Beamin]

Often in astronomy they talk about gas with temperatures of 2.7k but the gas is tens of H atoms per sq. meter so they aren't going to interact I don't think. If they did they would form H2. Maybe they are talking about the speed of the particles and extrapolating a temp and this is just dumbed down?

It's not about interacting (as in bumping against each other), it's a question of scale. If you look at a cubic lightyear of space, you can measure the temperature of the radiation it is emitting (or equivalently, the temperature of a hypothetical black body it is in equilibrium with). That temperature would be 2.7 K.

(By the way, take care about your units. "K" uppercase is kelvin, "k" lowercase is kilo-.)

(And by the by the way, "H atoms" don't exist individually. They form H₂ molecules where two hydrogen atoms are joined together.)

In space you can have H atoms in very diffuse gas. Especially where a lot of space has one hydrogen per cubic meter. The H2 gets broken apart by light/radiation and is so thinly spread that it never has a chance to encounter another hydrogen or other atom. You will see in astronomy a lot of "atomic elements" that are normally N2 H2 F2 Cl2 Br2 02 sure on earth we don't see this but that's because we have lots of pressure. You also don't see liquids in space. The exceptionis in flames for a short period of time.