Identify the Ideal Reversible Cycle – Process Combination A thermodynamic cycle composed of two isothermal processes and two isentropic (adiabatic, reversible) processes is known as the Carnot cycle. Choose the correct name for this cycle.

Introduction / Context:
Recognizing cycles from their process makeup is a core skill for thermodynamics and heat-engine analysis. The Carnot cycle is the gold standard for maximum possible efficiency between two fixed temperatures, consisting of perfectly reversible legs only. This question tests identification based on process types.

Given Data / Assumptions:

• Two isothermal processes (heat addition at T_H and heat rejection at T_L).
• Two isentropic processes (reversible adiabatic compression and expansion).
• Ideal reversible behavior with no entropy generation.

Concept / Approach:

Among classical cycles, only the Carnot cycle pairs isothermal legs with isentropic legs. The Stirling cycle uses isothermal plus constant-volume regenerative legs. The Ericsson cycle uses isothermal plus constant-pressure regenerative legs. The Joule (Brayton) cycle has isentropic legs with constant-pressure heat addition/rejection. Therefore, “two isothermal + two isentropic” uniquely identifies Carnot.

Step-by-Step Solution:

Verification / Alternative check:

On a T–s diagram, Carnot appears as two horizontal lines (isotherms) connected by two vertical lines (isentropes). This geometric signature is unique among the classical textbook cycles.

Why Other Options Are Wrong:

Each alternative contains different non-isothermal heat-transfer legs or lacks isothermal processes entirely, disqualifying them from the given description.

Common Pitfalls:

Confusing Stirling and Ericsson because both can, in principle, approach Carnot efficiency with perfect regeneration, yet their process types differ from Carnot’s definition.

Final Answer:

Carnot cycle