- #1
FireBones
- 103
- 0
Hello all,
I'm trying to put as precise a finger as I can on the quantum-mechanical description of conduction so I could explain it to, say, a curious 8th grader. The goal here is not to be able to perform calculations but give an explanation that does not suffer the errors of the Drude model. Unfortunately, the Wikipedia article for Quantum Conductivity is sorely lacking.
These are the questions I'm particularly interested in answering (at least to myself) before trying to frame an 8th-grader explanation.
I understand that electrons suffer no resistance in a perfect lattice due to diffraction, but that scattering occurs only due to imperfections in the lattice. At room temperature in a wire, these are mostly attributable to thermal vibrations of the ions.
My questions on this topic are:
A. How imperfections cause scattering? Do they disrupt phonons locally? If an electron's wavelength is too large to be scattered by a lattice where the ions are spaced, say 4 Angstroms apart, how does a missing ion or other imperfection leave the electron prone to scattering (after all, the wavelength of a slow electron is greater than 8 Angstroms, so why does a missing ion matter?)
B. What constitutes an electron-phonon interaction? If you had a movie camera and could document what this meant visually, what would it look like?
C. In the quantum-mechanical model, what causes heat dissipation? Perhaps the answers to "A" and "B" above will answer this question. Even in the semi-classical picture, it seems there is a bit of explaining to do since a moving electron interacting with a (moving) ion will not necessarily increase the speed of the ion, especially if the electron is glancing off the ion and the ion was moving toward the electron due to thermal vibrations.
D. What relevance do the vibrational modes induced by the electric field have on the transport of electrons with in the wire? Is it better to say these modes are induced by individual drifting electrons or due to the field itself caused by the charge separation in the wire? Does the fluctuating EM field due to these vibrations modulate and moderate the flow of electrons (like a string of revolving doors that facilitate the flow of electrons at specific speeds)?
E. Is any of the above discussion significantly different when comparing conduction in a normal-width circuit wire versus what is going on inside a filament of a lightbulb?
I'm hopeful the post-ers here will be gentle in trying to explain these things in a way that could be conveyed without resorting to the underlying wave mathematics. I'm writing a book on commonly mis-taught science and I'm really trying to explain this more accurate model in the chapter dealing with circuits, etc.
I'm willing to simply state outright certain things, like that an electron can propagate unhindered through a perfect lattice, without explaining diffraction or wave-particle duality. I just want to pick my battles in this regard and explain anything that is easy to explain.
Thanks so much!
I'm trying to put as precise a finger as I can on the quantum-mechanical description of conduction so I could explain it to, say, a curious 8th grader. The goal here is not to be able to perform calculations but give an explanation that does not suffer the errors of the Drude model. Unfortunately, the Wikipedia article for Quantum Conductivity is sorely lacking.
These are the questions I'm particularly interested in answering (at least to myself) before trying to frame an 8th-grader explanation.
I understand that electrons suffer no resistance in a perfect lattice due to diffraction, but that scattering occurs only due to imperfections in the lattice. At room temperature in a wire, these are mostly attributable to thermal vibrations of the ions.
My questions on this topic are:
A. How imperfections cause scattering? Do they disrupt phonons locally? If an electron's wavelength is too large to be scattered by a lattice where the ions are spaced, say 4 Angstroms apart, how does a missing ion or other imperfection leave the electron prone to scattering (after all, the wavelength of a slow electron is greater than 8 Angstroms, so why does a missing ion matter?)
B. What constitutes an electron-phonon interaction? If you had a movie camera and could document what this meant visually, what would it look like?
C. In the quantum-mechanical model, what causes heat dissipation? Perhaps the answers to "A" and "B" above will answer this question. Even in the semi-classical picture, it seems there is a bit of explaining to do since a moving electron interacting with a (moving) ion will not necessarily increase the speed of the ion, especially if the electron is glancing off the ion and the ion was moving toward the electron due to thermal vibrations.
D. What relevance do the vibrational modes induced by the electric field have on the transport of electrons with in the wire? Is it better to say these modes are induced by individual drifting electrons or due to the field itself caused by the charge separation in the wire? Does the fluctuating EM field due to these vibrations modulate and moderate the flow of electrons (like a string of revolving doors that facilitate the flow of electrons at specific speeds)?
E. Is any of the above discussion significantly different when comparing conduction in a normal-width circuit wire versus what is going on inside a filament of a lightbulb?
I'm hopeful the post-ers here will be gentle in trying to explain these things in a way that could be conveyed without resorting to the underlying wave mathematics. I'm writing a book on commonly mis-taught science and I'm really trying to explain this more accurate model in the chapter dealing with circuits, etc.
I'm willing to simply state outright certain things, like that an electron can propagate unhindered through a perfect lattice, without explaining diffraction or wave-particle duality. I just want to pick my battles in this regard and explain anything that is easy to explain.
Thanks so much!