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⚛️ Physics  ·  Thermodynamics  ·  NEET & JEE

Heat engine takes 1000 J from hot source, does 400 J of work. Heat rejected to cold reservoir:

Answer: 600 J.

  • A 400 J
  • B 500 J
  • C 600 J
  • D 1000 J

Correct answer: C. 600 J

Explanation: Energy conservation: Q<sub>hot</sub> = W + Q<sub>cold</sub>. Q<sub>cold</sub> = 1000 - 400 = 600 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.

Read the full Thermodynamics notes →