Question

Based on second law of thermodynamics the loss in available energy is being quantified as

• A. Irreversibility
• B. Decrease in available energy
• C. Entropy loss
• D. Energy loss

Hint:

Gouy-Stodola Theorem is key here: $\text{Irreversibility } (I) = T_0 \times \Delta S_{\text{universe}}$. It represents the direct translation of the Second Law of Thermodynamics into lost work potential.

Answer 1

The Correct Option is A

Concept: Real thermodynamic processes are accompanied by irreversibilities, such as friction, unresisted expansion, heat transfer across finite temperature differences, and mixing. These factors degrade the quality of energy, diminishing its capacity to perform useful mechanical work. According to the

Gouy-Stodola Theorem, the loss of available energy (or the destruction of exergy) is directly proportional to the total entropy generation ($\Delta S_{\text{gen}}$) within the universe during a process: \[ I = W_{\text{max}} - W_{\text{actual}} = T_0 \cdot \Delta S_{\text{gen}} \] Where:

• $I$ is defined as the

Irreversibility of the process.

• $T_0$ is the ambient surrounding temperature (dead state temperature).

• $\Delta S_{\text{gen}}$ is the total entropy generation of the system and its surroundings.
This loss of work potential is explicitly quantified as irreversibility.

Step 1: Examine the physical interpretation of Irreversibility.
Irreversibility measures how much potential work is permanently lost due to non-ideal behavior in a real-world process. It acts as the direct metric for the degradation of high-grade work potential into low-grade thermal waste.

Step 2: Contrast with other options.

• Option (B) simply restates the question text rather than naming the established thermodynamic metric.

• Option (C) and (D) are descriptive properties but do not represent the exact quantitative term for lost work potential.
Thus, the technical term used to quantify the loss in available energy according to the second law is Irreversibility, which matches Option (A).