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Show that the claims made in the backbone text are
actually true (for room temperature = 300 K). Use the following
equations taken from the backbone |
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For the
average velocity
v0 of a particle zooming around in the crystal: |
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v0 |
= |
æ
ç
è |
3kT
m |
ö
÷
ø |
1/2 |
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For the
mean time t between scattering: |
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For the
drift velocity
vD |
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For the minimal
mean free path length
lmin obtained for vD = 0: |
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Of course, you need numbers for the concentration
n of the free carriers and for the specific conductivity s |
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Since we are essentially considering metals,
you assume for a start that you have 1 free electron per atom if you
want to find a number for n. Here are a few data needed for the
calculation: |
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Atom |
Density
[kg · m3] |
Atomic weight
× 1,66 · 1027 kg |
Conductivity s
× 105 [W1 ·
m1] |
Conzentration Atoms n
[m3] ??? |
Na |
970 |
23 |
2.4 |
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Cu |
8.920 |
64 |
5.9 |
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Au |
19.300 |
197 |
4.5 |
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You may run into some trouble with the dimensions.
Just look at conversions from, e.g. [eV] to [J], from W to V and A, and at the relations
beween Volt, Ampere, Watts and Joule. |
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© H. Föll