# Homework Help: Thermodynamics/stirling engines

1. Oct 30, 2012

### hahaha158

1. The problem statement, all variables and given/known data

Helium Gas (Cv=12.5) has initial temperature T1, pressure P1, and volume V1. It follows a stirling engine cycle, namely it is 1)heated at constant volume to a temperature T2 then is 2)expanded isothermally to volume V2. 3) It is then returned to a temperature T1 by an isochoric process, then 4) returned to volume V1 by an isothermal process

2. Relevant equations

Q=deltaU+W
pv=nRT
Q=nCvdeltaT

3. The attempt at a solution

Because processes 1 and 3 are isochoric, that means there is no work done, so I neglected the calculations from those two processes. For both process 2 and 4 i set Q=W because it is isothermal and I believe we assume that it is an ideal gas. I tried using Q=nCvdeltaT to solve for Q of the two processes, and then subtract them from each other, but I found I would end up with

nCvT2-nCvT1
net work=nCv(T2-T1)

It seems too simple, am I doing something wrong?