# Homework Help: Thermodynamics system

1. Oct 20, 2014

### decerto

1. The problem statement, all variables and given/known data
Design an explicit system which does the following: It goes adiabatically and reversibly from state A to B. Then it returns from state B to state A probably irreversibly and receiving some heat from the outside world on the way. It cant give out heat.

2. Relevant equations
$PV^{\gamma}=c$ for an adiabatic process
$PV=c$ for an isothermal process

3. The attempt at a solution

I attempted to draw various 3 step PV diagrams using isobaric and isochoric steps but they all gave out heat. The only way I can think of doing this is if the adiabatic process is the same as an isothermal process i.e
$PV^{\gamma}=PV$
$\gamma=1$
$C_p=C_v$

But this can't be true for an ideal gas so I have no idea.

2. Oct 20, 2014

### Staff: Mentor

Doesn't that depend on the direction of the process?

3. Oct 20, 2014

### decerto

Yes but amn't I forced into a direction that gives out heat after an adiabatic process then a process which takes in heat if I want to get back to the start?

4. Oct 21, 2014

### Staff: Mentor

I haven't worked out the details, but if your adiabatic process is an expansion, can't you go back to state A without any heat leaving the system?