JEE Main · 2025 · Shift-IIhardTHERMO-141

Arrange the following in order of magnitude of work done by the system / on the system at constant temperature: (a)…

Thermodynamics · Class 11 · JEE Main Previous Year Question

Question

Arrange the following in order of magnitude of work done by the system / on the system at constant temperature:

(a) ∣Wreversible∣|W_{\text{reversible}}| for expansion in infinite stage. (b) ∣Wirreversible∣|W_{\text{irreversible}}| for expansion in single stage. (c) ∣Wreversible∣|W_{\text{reversible}}| for compression in infinite stage. (d) ∣Wirreversible∣|W_{\text{irreversible}}| for compression in single stage.

Options
  1. a

    a>b>c>da > b > c > d

  2. b

    d>c=a>bd > c = a > b

    ✓
  3. c

    c=a>d>bc = a > d > b

  4. d

    a>c>b>da > c > b > d

Correct Answerb

d>c=a>bd > c = a > b

Detailed Solution

🧠 Reversible expansion maximizes work out; irreversible compression maximizes work in For isothermal processes between the same two states, the ranking of ∣w∣|w| follows from the second law: reversible expansion gives the most work from the system, while single-stage (irreversible) compression requires the most work input.

Ranking by magnitude of work:

  • dd (irreversible compression, single stage): highest — surroundings push at the high final pressure throughout.
  • c=ac = a (reversible compression = reversible expansion): equal in magnitude, intermediate.
  • bb (irreversible expansion, single stage): lowest — system pushes at the low external pressure throughout.

Order: d>c=a>bd > c = a > b

Answer: (b) d>c=a>b\boxed{\text{Answer: (b) } d > c = a > b}

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