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JEE Main 202624 JanuaryEvening Shift
Exam
JEE Main
Year
2026
Date
24 January
Shift
Evening Shift
Subject
Physics
Chapter
Thermodynamics

JEE Main 2026 · 24 January · Evening Shift · Physics · Thermodynamics

10 mole of an ideal gas is undergoing the process shown in the...

10 mole of an ideal gas is undergoing the process shown in the figure. The heat involved in the process from P1toP2P_{1} to P_{2} is α\alpha Joule (P1=21.7 PaP_{1}=21.7 \mathrm{~Pa} and \left.P_{2}=30 \mathrm{~Pa}, \mathrm{C}_{v}=21 \mathrm{~J} / \mathrm{K}. \mathrm{mol}, R=8.3 \mathrm{~J} / \mathrm{mol}. \mathrm{K}\right).Thevalueof. The value of\alphaisis\_\_\_\_.
10 mole of an ideal gas is undergoing the process shown in the figure. The heat involved in the process from P_ 1 to P_

Options

  1. A21
  2. B15
  3. C28
  4. D24

Correct answer

A. 21

Step-by-step solution

From the given P−VP-V diagram, the process from P1P_1 to P2P_2 is an isochoric process because the volume remains constant at V=1 m3V = 1\text{ m}^3.
For an isochoric process, the work done W=0W = 0.
According to the first law of thermodynamics, the heat involved is Q=ΔU+W=ΔUQ = \Delta U + W = \Delta U.
The change in internal energy is given by ΔU=nCvΔT\Delta U = n C_v \Delta T.
Using the ideal gas equation PV=nRTPV = nRT, we have nΔT=VΔPRn\Delta T = \frac{V\Delta P}{R}.
Substituting this into the expression for QQ:
Q=Cv(V(P2−P1)R)Q = C_v \left( \frac{V(P_2 - P_1)}{R} \right)
Given values: n=10n = 10 moles, V=1 m3V = 1\text{ m}^3, P1=21.7 PaP_1 = 21.7\text{ Pa}, P2=30 PaP_2 = 30\text{ Pa}, Cv=21 J/mol⋅KC_v = 21\text{ J/mol}\cdot\text{K}, and R=8.3 J/mol⋅KR = 8.3\text{ J/mol}\cdot\text{K}.
Q=21×1×(30−21.7)8.3Q = 21 \times \frac{1 \times (30 - 21.7)}{8.3}
Q=21×8.38.3=21 JQ = 21 \times \frac{8.3}{8.3} = 21\text{ J}.
Thus, the value of α\alpha is 21.
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