Thursday, April 12, 2012
Hall coefficient and Lorenz number
So, starting to look back through the material from the beginning of semester,
We have the Hall effect, which is the potential difference that we get in a conductor perpendicular to a current.
The Hall coefficient is the ratio of the transverse electric field to the product of the current and magnetic field, i.e. Ey/jxH.
We have the Lorenz number which is the ratio of κ/σT essentially a ratio between the thermal and electrical conductivity.
Now, electrical conductivity would appear in the Hall coefficient in the current term. Can't see how the thermal term would enter the Hall coefficient.
Likewise, can't see how the magnetic field would enter the Lorenz number.
Besides being able to find an expression for both from the Drude model, are they (physically) related?
(Sorry if this sounds a bit random, my notes are quite squished together...)
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Well, I look at it like this:
ReplyDeleteThe Hall coeffivient and the Lorenz number are just looking at different properties of the material, so I guess in that sense they are related/unrelated, if you catch my drift...
Remember that alot of the material in C1 of A&M is dealing with conductivity, which is the thing that links the above two concepts. This is due to the fact that we can obtain Ohm's law in a fairly straight forward manner from Drude, so it makes sense to look at different properties, in terms of conductivity.
Ah.
ReplyDeleteThe Hall coefficient and Lorenz number describe transport properties of the material.
Drude gives Ohm's law, which gives us electrical conductivity.
So, Hall is sort of like ratio of how directional our motion is (since we induce a magnetic field).
Compare with Lorenz, which is like a condition on my thermal (electrical) conductivity given such an electric (thermal) conductivity.
Thanks Dave.