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⚛️ Physics  ·  Thermodynamics  ·  NEET & JEE

For a gas expanding adiabatically, gamma = Cp/Cv = 5/3. If pressure halves, volume changes by factor:

Answer: 2 5/3.

  • A 2
  • B 2<sup>3/5</sup>
  • C 2<sup>5/3</sup>
  • D 3/5

Correct answer: C. 2<sup>5/3</sup>

Explanation: PV<sup>gamma</sup> = constant. P<sub>1</sub> V<sub>1</sub><sup>5/3</sup> = P<sub>2</sub> V<sub>2</sub><sup>5/3</sup>. V<sub>2</sub><sup>5/3</sup> = (P<sub>1</sub>/P<sub>2</sub>) V<sub>1</sub><sup>5/3</sup> = 2 V<sub>1</sub><sup>5/3</sup>. V<sub>2</sub> = 2<sup>3/5</sup> V<sub>1</sub>. Answer: 2<sup>3/5</sup>.

Carnot Cycle (P-V Diagram)VP1→2: isothermal expansion (T_H)2→3: adiabatic expansion3→4: isothermal compression (T_C)4→1: adiabatic compression1234Net work done by the gas = area enclosed by the loop 1→2→3→4→1

The Carnot cycle alternates two isothermal steps (heat absorbed at TH, released at TC) with two adiabatic steps (no heat exchange); the enclosed loop area equals the net work output, and η = 1−TC/TH is the maximum possible efficiency between those two temperatures.

Concept context

Laws of thermodynamics, heat engines, entropy, and gas processes.

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