
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
v_{0} of a particle zooming around in the crystal: 


v_{0} 
= 
æ
ç
è 
3k_{B}T
m 
ö
÷
ø 
1/2 




For the
mean time t between scattering: 





For the
drift velocity
v_{D} 





For the
mean free path length
l obtained for v_{D} = 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 m^{–3}] 
Atomic weight
[1.66 · 10^{–27} kg] 
Conductivity
s
[10^{7} W^{–1}
m^{–1}] 
Atomic density n
[m^{–3}] ??? 
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. 

