Wiedemann-Franz law

I have seen a number of posts here regarding the use of aluminum heat
sinks. I have read only a few of them. For anyone seriously interested
in the topic, they should read up on the Wiedemann-Franz law. A good
place to start is the Wikipedia article on the Wiedemann-Franz law.
This law states that there is a temperature dependent ratio of thermal
to electrical conductivities that does not depend on the metal. As
typical for such "laws" they are only approximately correct. The
interesting physics is in the deviations from Wiedemann-Franz law. This
law seems to work well for good electrical conductors. The law is based
upon the assumption that energy in a metal is carried primarily by
electrons. Obviously, even excellent electrical insulators can conduct
For good conductors such as aluminum, one should look at what limits
electrical conductivity. Some of the limitations that limit conductivity
in silver, copper, and aluminum are lattice defects. These include
impurities and dislocations. Thus, best conductivity will be achieved
with pure and annealed materials.
The other main difference will be in the interactions of electrons with
phonons or lattice vibrations. That will give the main contribution to
the Wiedemann-Franz ratio.
I do not wish to create a discourse on the subject. These are available.
I just point out the situation.
Reply to
Salmon Egg
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