And what is the practical difference between “current flow gives the gas atoms or molecules some extra energy which they then give up in the form of a photon” and “current flow gives the gas atoms or molecules some extra heat, lifting the electrons to an excited state which they then give up in the form of a photon”?
Same difference, the current excites the electron in the atom raising it to a higher energy state. When it falls from that state it emits a photon. Precisely the same as the current heating the atom and exciting the electron to that state. Neon lights operate by direct electron bombardment for excitation rather than electron conduction so the emmison spectrum is narrower, but the process is the same: that of energy applied to an atom increasing the electronic state which allows later re-emmsion as visible light.
That’s like saying that a plane and a car are the same because they both get you where you need to go. Just because the end result is similar does not mean the mechanisms are similar, as well. In a hot object, the individual atoms or molecules all have different energy levels with a more or less random distribution, so you get a basically continuous spectrum with a distinct Gaussian curve - the so-called blackbody spectrum. In this case, the heat imparts energy to the whole atom or molecule. In electrical stimulation, the energy is only imparted to the valence electrons, and is basically the same for each atom or molecule (quantum effects smear things out so the output is not 100% monochromatic). The point is, it’s easy as a practical matter to tell the difference between light produced by incandescence and light produced by electrical stimulation. All you have to do is look at the spectra.
Damn, and here I was thinking that this was going to be a completely objective (since it’s GQ) discussion of which of two women was better looking. With pictures, of course.
Hey, thanks, comma. Dunno if I’ll be around quite as much as I used to, but I’ll try to drop by from time to time. Nice to see some of the old gang is still here.
Your post requires some correction and clarification.
Temperature is a measure of the average kinetic energy of a group of molecules, not a measure of the average speed. Heat is not something that an object has, it’s usually considered something that is being transferred from one object to another. If you were to talk about the “heat” of an object, you’d be better off talking about the internal energy of the body, which is temperature times the number of molecules (times some constant.)
Well, higher flow rate means more heat flowing through the shower head (i.e. heat flowing from your hot water tank to your cold shower/body.) That would mean that you might feel warmer with more water flowing over your body, just like you feel colder when the wind is blowing rather than standing still - your body has a constant supply of new surrounding fluid, whereas with less flow the fluid stays near you and cools off/warms up a little. But, water at a certain temperature will ALWAYS transfer heat to you at exactly the same rate. It’s just that if you have more water at that temperature it doesn’t have time to cool off and transfer heat more slowly.
And, the difference between the heat transferred to your body from air and water is due to differences in thermal conductivity of water versus air. And once you start to transfer heat from the water/air to your body, you start to decrease the temperature of the water/air in accordance with the water/air’s specific heat.
Thermal density? What’s that? I think maybe you mean specific heat. And, for metals, it appears that molar heat capacity is about the same, which means that heat capacity in metals depends on atomic weight as well as density. Iron has both a higher specific heat and a higher thermal conductivity than lead, meaning I’d rather touch a hot lead thing than a hot iron thing of the same mass. Lead is only about 50% denser than iron, but has 1/3 the specific heat of iron. So, I’d also rather touch a hot lead thing than a hot iron thing of the same volume. I do not know whether molten lead would have much different thermal conductivity than solid lead, but one thing to keep in mind about touching liquids is you have more ways to get heat into you than with solids - just as in your shower or in a wind, flowing fluid gives better heat transfer because you have fresh hot stuff to burn you.
