Figure below shows two paths that may be taken by a gas to go from a… | NEET 2015 (AIPMT, Cancelled Paper)

Q71NEET 2015 · AIPMT · CANCELLED PAPERMedium

P-V Diagrams & Cyclic Processes

Figure below shows two paths that may be taken by a gas to go from a state A to a state C.

In process AB, 400 J of heat is added to the system and in process BC, 100 J of heat is added to the system. The heat absorbed by the system in the process AC will be

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Answer: (a)

From the figure: $V_A = 2 \times 10^{-3}$ , $V_C = 4 \times 10^{-3}\ \text{m}^3$ ; $P_A = 2 \times 10^4$ , $P_B = P_C = 6 \times 10^4\ \text{Pa}$ .
Path ABC: $Q = 400 + 100 = 500\ \text{J}$ , $W = W_{BC} = 6 \times 10^4 \times 2 \times 10^{-3} = 120\ \text{J}$ , so $\Delta U = 380\ \text{J}$ .
Path AC (trapezium): $W = \frac{1}{2}(2 + 6) \times 10^4 \times 2 \times 10^{-3} = 80\ \text{J}$
$Q_{AC} = \Delta U + W = 380 + 80 = 460\ \text{J}$
So the answer is (a) 460 J.

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

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