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NEET 2015 (AIPMT, Cancelled Paper) · P-V Diagrams & Cyclic Processes

P-V Diagrams & Cyclic Processes question from NEET 2015 (AIPMT, Cancelled Paper)

Q70NEET 2015 · AIPMT · CANCELLED PAPERMedium

P-V Diagrams & Cyclic Processes

One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure.

Figure

The change in internal energy of the gas during the transition is

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Answer: (d)

  1. Diatomic: ΔU=52nRΔT=52(PBVB−PAVA)\Delta U = \frac{5}{2}nR\Delta T = \frac{5}{2}(P_BV_B - P_AV_A).
  2. PAVA=5 kPa×4 m3=20 kJP_AV_A = 5\ \text{kPa} \times 4\ \text{m}^3 = 20\ \text{kJ}, PBVB=2×6=12 kJP_BV_B = 2 \times 6 = 12\ \text{kJ}
  3. ΔU=52(12−20)=−20 kJ\Delta U = \frac{5}{2}(12 - 20) = -20\ \text{kJ}
  4. So the answer is (d) −20-20 kJ.
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