According to Carnot Theorem:
"Of all engines working between two given temperature, none is more efficient than a carnot engine."
I want to know what actually is meant by an engine working between two temperatures? Is it always necessary that the engine should follow the Carnot cycle(four path) or would any other number of cyclic processes do the same?
"I think any engine would do the same because in the proof they do not use the fact that the engine (other than carnot) is not necessarily reversible!"
Now need a clarification!