 | 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 |
|
 | For the average velocity
v0 of a particle zooming around in the crystal: |
| |
v0 | = | æ ç è
| 3kT m | ö ÷ ø
| 1/2 |
|
|
|  | For the mean time t between scattering: |
| |
|
|  | For the drift velocity vD |
| |
|
|  | For the minimal mean free path length lmin obtained for
vD = 0: |
| |
|
 | Of course, you need numbers for the concentration
n of the free carriers and for the specific conductivity s |
|  | 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: |
| |
Atom | Density [kg ·
m3] | Atomic weight × 1,66 · 1027
kg | Conductivity
s × 105 [W1 ·
m1] | Conzentration Atoms n [m3]
??? | Na | 970 | 23 | 2.4 | | Cu | 8.920 | 64 | 5.9 | | Au | 19.300 | 197 | 4.5 | |
|
 | 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. |
|
|
© H. Föll (Advanced Materials B, part 1 - script)