Can please give me the idea for solving these questions
For 1., read this article: http://en.wikipedia.org/wiki/Thermal_efficiency
Pay special attention to the section on Carnot efficiency.
I have efficiency = 1 - Tlow /T high
so 1 - 200/1200
efficiency = 5/6
Carnot efficiency = w/Qh
20/40 = 0.5
then what the next ?
Why is the Carnot efficiency important? Can a given process have a greater efficiency than the Carnot value?
I don't no the important but I can not the efficiency greater than the Carnot value
So, based on the Carnot efficiency of the process, and the efficiency determined by the heat input and work output, is the process feasible?
BTW, if you read the wiki article, it tells you why the Carnot efficiency is important.
Separate names with a comma.