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⚛️ Physics  ·  Thermodynamics  ·  NEET & JEE

A monatomic ideal gas (γ = 5/3) at 300 K is compressed adiabatically to one-eighth of its original volume. The final temperature is:

Answer: 1200 K.

  • A 600 K
  • B 900 K
  • C 1200 K
  • D 2400 K

Correct answer: C. 1200 K

Explanation: T<sub>2</sub> = T<sub>1</sub>(V<sub>1</sub>/V<sub>2</sub>)<sup>&gamma;&minus;1</sup> = 300 &times; 8<sup>2/3</sup> = 300 &times; 4 = 1200 K.

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.

Read the full Thermodynamics notes →