Question

The conclusion of second law of thermodynamics is that

• A. No heat engine can have efficiency $\eta$ equal to zero.
• B. No heat engine can have efficiency $\eta$ equal to one.
• C. No heat engine can have efficiency $\eta$ greater than one.
• D. No heat engine can have efficiency $\eta$ less than one.

Answer 1

Answer: (B)

No heat engine can have efficiency $\eta$ equal to one.

Answer 2

: The efficiency $\eta = 1$is maximum efficiency, it shows that the heat engine is 100% efficient which is practically not possible.