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Friday, 9 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 18 March 2021, Shift 1, Physics Q4

Question 4 of 90 in this shift, Physics question 4 of 30, Section A.

The P-V diagram of a diatomic ideal gas system going under cyclic process as shown in figure. The work done during an adiabatic process CD is (use γ=1.4\gamma = 1.4) :

The figure, in words

P-V diagram: A (V=1, P=200 N/m^2), B (V=1, P=100), C (V=4, P=100), D (V=3, P=200). Cycle A->B (down), B->C (right, isobaric), C->D (adiabatic curve), D->A (left, isobaric). P in N/m^2, V in m^3.
  1. (1)400 J
  2. (2)−500-500 JOfficial answer
  3. (3)200 J
  4. (4)−400-400 J

Official answer

Option 2

NTA final key.

Chapter
Thermodynamics
Topic
Thermodynamic Processes
Idea tested
Adiabatic Process Analysis

Same idea in other shifts

Asked 8× in all
  1. 6 Apr 2026, Shift 2 · Q30A cylinder with adiabatic walls is closed at both ends and is divided into two compartments by a frictionless adiabatic piston. Ideal gas…HardSingle correct
  2. 2 Apr 2025, Shift 1 · Q31In an adiabatic process, which of the following statements is true ?EasySingle correct
  3. 2 Apr 2025, Shift 2 · Q32Identify the characteristics of an adiabatic process in a monoatomic gas. (A) Internal energy is constant. (B) Work done in the process is…MediumOther
  4. 8 Apr 2025, Shift 2 · Q33A monoatomic gas having γ=53\gamma = \frac{5}{3} is stored in a thermally insulated container and the gas is suddenly compressed to…EasySingle correct
  5. 9 Apr 2024, Shift 1 · Q38A sample of 11 mole gas at temperature T is adiabatically expanded to double its volume. If adiabatic constant for the gas is…MediumSingle correct
  6. 9 Apr 2024, Shift 1 · Q39The volume of an ideal gas (γ=1.5\gamma=1.5) is changed adiabatically from 55 litres to 44 litres. The ratio of initial pressure to final…EasySingle correct
  7. 25 Jul 2022, Shift 1 · Q37A certain amount of gas of volume VV at 27∘27^\circC temperature and pressure 2×107 Nm−22\times10^{7}\ \mathrm{Nm^{-2}} expands isothermally until…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.