Question

Which law of thermodynamics says that efficiency of a heat engine cannot be 1?

(a) First

(b) Zeroth

(c) Second

(d) Third

Answer 1

Right option is (c) Second

Explanation: The second law of thermodynamics fundamentally disallows many processes that may be consistent with the law of conservation of energy. It says that entropy change in an irreversible process has to be positive. This means that heat given to an engine can’t all be converted into work. Therefore, efficiency cannot be 1.