# Calculating thermal efficiency, I need HELP

1. Dec 11, 2013

### Eagle's Wings

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

You build a heat engine that takes 1.00 mol of an ideal diatomic gas through the cycle abc, where segment bc is isobaric and segment ca is isochoric. calculate the thermal efficiency of the engine.

this is a 5 part problem and I already solved for Wo and Wo=Qo I solved for Ta, Tb, and Tc. Ta=Tb. the problem gives me Va, Vb, Pa, and Pb in the figure.

2. Relevant equations

e = W/Q$_{H}$ = 1 - |Q$_{C}$/Q$_{H}$|

W = |Q$_{H}$| - |Q$_{C}$|

3. The attempt at a solution

I know that there are other ways to solve for e, but I don't know how to solve for e in this problem. I am completely lost. I cant use Carnot because thats for an ideal system, I cant use the one for the otto cycle because i dont have r and the problem doesnt tell me that it is otto cycle problem. WHAT DO I DO?

2. Dec 11, 2013

### Eagle's Wings

also the segment ab is isothermic. I dont see how that would help any though

3. Dec 11, 2013

### Eagle's Wings

just kidding, i just figured it out. i can use the equation of heat entering the system which is Qh which is on segment bc which is isobaric so i can use Cp to solve for Qh!!!