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The changing of internal energy is equal the work

  U  l , where l  C T  T     U or
q q  1 2

R R RT   P  K K 1 



l 
l  T  T 2 ; q  VP 1 1  P 2 V 2 ; q  1 1   2  ; (2.14)
l


1
q
k  1 k  1 k 1   P 1  
 


The changing of the entropy is equal zero
s  0 .

2.5 Polytrophic process of gas
Polytrophic process — any process changing of thermodynamics co-ordinates which
is going at the constant value of specific heat.
n n 1  n 1
P 2  V  T  V  T  P  n
1
For this process:    ; 2   1  ; 2   2  (2.15)






P V T V T P
1  2  1  2  1  1 
And work will be equal:
 k 1 
1 R RT   P  n 
l   VP  P V   T  T   1 1   2 
n 1 1 2 2 1 2     ; (2.14)
n 1 n 1 n 1  P 
 1 


R

Heat for this process: q   U  l  C V T  T 1  T  T 2 ; (2.15)
n
1
2
n  1
T 2
Change of entropy:  s  C n m ln ; (2.16)
T
1
C  C
Polytrophic constant n  n P ; (2.17)
C  C
n V
n  k
Polytrophic specific heat C n  C V (2.18)
n  1

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