Why do real engines never attain the efficiency of the Carnot cycle?
-First, they don't use the carnot cycle because its acts slowly.
-Second, all real engines produce friction and other losses.
So what type are processes are we talking about?
Carnot cycle: reversible processes require infinite time to complete.
"Real engine:" processes are completed in finite time, and are, therefore, irreversible, meaning more heat is lost in increasing the entropy of the universe.
Here you will have more clarification:
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