The wiedemann franz law (1853 states that the ratio of the thermal conduc- tivity, k, to the electrical conductivity, σ, of metals is directly proportional to the absolute temperature with a proportionality constant independent of the metal. let us see how one can derive this from elementary considerations of diffusion. go back to our elementary derivation of the relation between the particle current 3p and the particle density in one dimension which, with the definition d δ2/t gave 3p =-d(0p/or). now consider a similar situation, but in which the particle density is uniform whereas the particles carry energy which varies in position, e(r). show that the energy current, je which is the energy which crosses from left to right per unit time per unit area is in the one-dimensional model de dt dr dt dr where ρ is the number of particles per unit volume and cu is the specific heat de/dt. thus pcd. in class i showed that, for a system with one carrier, the electrical conductivity was σ-pe2d/kt so that k c which is the wiedemann franz law. if, in addition, one assums for c the classical value of an ideal gas, 3k/2 one obtains for the ratio (3/2)(k/e)t. this coefficient turns out to be about 1/2 the value measured experimentally, so the basic idea is correct that both with the value of cy i processes are simply diffusive, but there is something wrong
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Physics, 21.06.2019 22:30, makayladurham19
25pts the diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?
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Physics, 22.06.2019 17:40, tylercapozzoli
Scientists follow specific processes in order to determine valid explanations and conclusions from observations. david observed strange lights in the sky above his home outside of roswell, new mexico. the only explanation that makes sense to him is that there are ufos in the area. what should david do next to verify his explanation?
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The wiedemann franz law (1853 states that the ratio of the thermal conduc- tivity, k, to the electri...
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