In the P-V diagram below, the cyclic process consists of the segment A-B that is
ID: 2302221 • Letter: I
Question
In the P-V diagram below, the cyclic process consists of the segment A-B that is an isovol,
B-C that is an adiabat and C-A that is an isotherm at T=300K. The working gas in the system
is diatomic, with ?=1.40.
a)what is the pressure and temperature at point B?
b)Find ?Eint, Q and W for each of the three segments of the cycle and display them in a table
c)what is the work done per cycle and the ef?ciency of the cycle? How does this efficiency
compare to that of a Carnot cycle operating between the maximum and minimum temperatures
of this system?
Explanation / Answer
you havent given the pv diagram
but still you could help yourself
Q = ?U + W
here
Q is +ve if heat is put into system ,?U is +ve if temp increases,W is +ve for expansion(work done by gas)
for isothermal process ?U = 0 as Ti=Tf ? Q = W=nRT ln(Vf/Vi)
for constant pressure process (horizontal line on pv) if Vf>Vi (or Tf>Ti from PV = nRT)
then W>0 ,?U>0 Q>0 Q = nCp?T W=P(Vf-Vi)
for constant volume process vertical line in pv diagram
W = 0 (as Vf=Vi) ; if Tf>Ti ?U>0 as ?U = nCv(Tf-Ti) ;Q = ?U