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⚛️ Physics  ·  Thermodynamics  ·  NEET & JEE

A gas releases 100 J of heat while 40 J of work is done on it. The change in its internal energy is:

Answer: -60 J.

  • A -140 J
  • B -60 J
  • C -100 J
  • D +60 J

Correct answer: B. -60 J

Explanation: &Delta;U = Q - W<sub>by gas</sub> = (-100) - (-40) = -60 J.

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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