Page 25 - 6413

 n e    
2
j  0 E , (37.5)
2 m  v 
e

from which the specific conductivity  is determined by the
formula (37.6)

n e 2   
  0 . (37.6)
2m  v 
e

where n is the concentration of electrons; <> - average length
0
of their free run; <v> - average rate of the chaotic movement of

electrons; m - the electron mass; е – its charge.
e
Classical physics only in the first approximation explained the
conductivity of metals and led to a number of conclusions that
contradicted the experimental data. It was due to quantum physics that

stated the way out of the difficulty.

2. Methodology of experimental determination of the specific

resistance of the conductor and verification of Ohm’s Law.
As follows from (37.2), the specific resistance of the conductor
can be calculated by the formula (37.7)

RS
  . (37.7)
l

Thus, in order to determine the resistivity, it is necessary to
measure its resistance R, the length of the conductor l, and the area of

the cross-sectional S. In this case, the resistance of the conductor is
determined by Ohm's law (37.1) by measuring the voltage U and the
current I. If we take a conductor with a diameter d, then its cross-

d  2
sectional area S  , and then the working formula for calculating
4
the specific resistance a conductor will take the form of (37.8)

24