# Homework Help: Thermodynamics monster task

1. Nov 30, 2014

### Amina

Some circle process contains next stages:
2. isochoric heating
4. isochoric cooling
If we put ideal gas(x=1.4) in this process from starting conditions :
-Volume (V=30dm3)
-Pressure (P= 2.026bar)
-Temperature (T=366K)
* in first stage volume lows down on 20dm3,
*on the second stage pressure goes on 4.13bar.
CALCULATE VALUE OF ALL WORK AND ALL HEATING CHANGES IN THIS CIRCLE PROCESS!
Result should be (delta) I>U =0 ;Q= -W= 453J

This is what i used to calculate but didnt get right result:
stage 1)
P1V1=nRT1 ---->n
Cv=5/2 R
Q=0
W=(delta) U= n Cv (delta)T ; delta T(T2-T1)
T1/T2= (V2/V1) exp (x-1) ------> T2
stage 2)
W=0
P1/P2= (V2/V1)exp (x) ----->P2
T2/T3=P2/P3 ----->T3
Q=nCv (delta)T ;delta T= (T3-T2)
stage 3)
T3/T4= (V4/V3) exp(x-1) ----->T4
Q=0
W=(delta)U= n Cv (delta)T ;delta T= ( T4-T3)
stage 4)
W=0
Q=(delta)U= n Cv (delta)T ; delta T= (T1-T4)

Did i messed smt with formulas? Calculating not problem, just this is a bit hard to visualise and set right formulas.. if someone can catch my mistake fast so i can try again, i dont want to bother anybary or take time. Thank you in front..
I m new here, sorry if didnt apsorb all rules at first.

Last edited by a moderator: Nov 30, 2014
2. Nov 30, 2014

### Staff: Mentor

Please show us some more details of your calculations. It's really hard to figure out where you went wrong without that.

Chet