Question

“It is impossible for a heat engine to be 100% efficient.” This statement is related to:

• A. First law of thermodynamics
• B. Second law of thermodynamics
• C. Enthalpy
• D. Diffusion

Hint:

The Second Law of Thermodynamics limits the efficiency of all heat engines — always link efficiency-related impossibilities to this law, not the first law or enthalpy.

Answer 1

The Correct Option is B

Step 1: The statement refers to the efficiency of a heat engine, which is fundamentally limited by the laws of thermodynamics. Step 2: The Second Law of Thermodynamics states that it is impossible for any heat engine to convert all the heat it absorbs into work — some energy must always be lost to a sink. This implies no engine can be 100% efficient. Step 3: The First Law of Thermodynamics only deals with conservation of energy and doesn't restrict efficiency. Concepts like enthalpy and diffusion are unrelated to the maximum efficiency of heat engines. Conclusion: The impossibility of 100% efficiency directly follows from the Second Law of Thermodynamics.