# Entropy chance with a carnot cycle?

1. Jul 29, 2010

### coffeem

in a carnot cycle the gas expands adiabatically from 200 degrees to 500 degrees. what is the efficecy? and what is the entropy change of the gas during the expansion?

sorry - i got the efficiency to be: 38.8%

however I am unsure how to work out the entropy chance? any hints???

2. Jul 29, 2010

### coffeem

however my thinking is that if the the system is adiabatic... then the entropy will stay constant.... then it will be 0??? am i on the right lines? thanks

3. Jul 30, 2010

### coffeem

Hi I am still struggling with this. any advice? thanks

4. Jul 30, 2010

### rock.freak667

If ΔS=dQ/T and dQ=0 for an adiabatic process then ΔS=0. So you are right.