A thermodynamic process is shown in the figure. The pressure and volumes corresponding to some points in the figure are PA = 3 × 10⁴ Pa; VA = 2 × 10⁻³ m³; PB = 8 × 10⁴ Pa; VD = 5 × 10⁻³ m³. In the process AB, 600 J of heat is added to the system and in process BC, 200 J of heat is added to the system. The change in internal energy of the system in process AC would be (a) 560 J (b) 800 J (c) 600 J (d) 640 J

Answer: (a). Along ABC: Q = 600 + 200 = 800 J; AB is isochoric ( W = 0). BC is isobaric at PB = 8 × 10⁴ Pa from V = 2 × 10⁻³ to 5 × 10⁻³ m³: W = 8 × 10⁴ × 3 × 10⁻³ = 240 J. Δ UAC = Q - W = 800 - 240 = 560 J So the answer is (a) 560 J.

A thermodynamic process is shown in the figure. The pressure and… | NEET 1991 (AIPMT)

Q92NEET 1991 · AIPMTMedium

P-V Diagrams & Cyclic Processes

A thermodynamic process is shown in the figure. The pressure and volumes corresponding to some points in the figure are $P_A = 3 \times 10^{4}\text{ Pa}$ ; $V_A = 2 \times 10^{-3}\text{ m}^3$ ; $P_B = 8 \times 10^{4}\text{ Pa}$ ; $V_D = 5 \times 10^{-3}\text{ m}^3$ . In the process $AB$ , 600 J of heat is added to the system and in process $BC$ , 200 J of heat is added to the system. The change in internal energy of the system in process $AC$ would be

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Answer: (a)

Along ABC: $Q = 600 + 200 = 800\ \text{J}$ ; AB is isochoric ( $W = 0$ ).
BC is isobaric at $P_B = 8 \times 10^4\ \text{Pa}$ from $V = 2 \times 10^{-3}$ to $5 \times 10^{-3}\ \text{m}^3$ : $W = 8 \times 10^4 \times 3 \times 10^{-3} = 240\ \text{J}$ .
$\Delta U_{AC} = Q - W = 800 - 240 = 560\ \text{J}$
So the answer is (a) $560\text{ J}$ .

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