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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Specific Heat Capacities of Gases

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Specific Heat Capacities of Gases

An ideal gas ( γ = 1.67 ) is taken through the process abc shown in...

An ideal gas (γ=1.67\gamma = 1.67) is taken through the process abcabc shown in the figure. The temperature at the point aa is 300 K300 \text{ K}. Calculate the amount of heat supplied in the path abab and in the path bcbc.
An ideal gas ( γ = 1.67 ) is taken through the process abc shown in the figure. The temperature at the point a is 300 K

Options

  1. A14.9 J14.9 \text{ J}, 24.9 J24.9 \text{ J}
  2. B14.9 J14.9 \text{ J}, 10.0 J10.0 \text{ J}
  3. C10.0 J10.0 \text{ J}, 15.0 J15.0 \text{ J}
  4. D24.9 J24.9 \text{ J}, 14.9 J14.9 \text{ J}

Correct answer

A. 14.9 J14.9 \text{ J}, 24.9 J24.9 \text{ J}

Step-by-step solution

From the given graph:

Path a→ba \rightarrow b is an isochoric process (constant volume) where V=100 cm3=10−4 m3V = 100 \text{ cm}^3 = 10^{-4} \text{ m}^3.
The pressure changes from Pa=100 kPa=105 PaP_a = 100 \text{ kPa} = 10^5 \text{ Pa} to Pb=200 kPa=2×105 PaP_b = 200 \text{ kPa} = 2 \times 10^5 \text{ Pa}.
The heat supplied at constant volume is given by:
Qab=nCVΔT=VΔPγ−1Q_{ab} = nC_V\Delta T = \dfrac{V\Delta P}{\gamma - 1}
Substituting the values:
Qab=10−4×(2×105−105)1.67−1Q_{ab} = \dfrac{10^{-4} \times (2 \times 10^5 - 10^5)}{1.67 - 1}
Qab=10−4×1050.67=100.67≈14.9 JQ_{ab} = \dfrac{10^{-4} \times 10^5}{0.67} = \dfrac{10}{0.67} \approx 14.9 \text{ J}

Path b→cb \rightarrow c is an isobaric process (constant pressure) where P=200 kPa=2×105 PaP = 200 \text{ kPa} = 2 \times 10^5 \text{ Pa}.
The volume changes from Vb=100 cm3=10−4 m3V_b = 100 \text{ cm}^3 = 10^{-4} \text{ m}^3 to Vc=150 cm3=1.5×10−4 m3V_c = 150 \text{ cm}^3 = 1.5 \times 10^{-4} \text{ m}^3.
The heat supplied at constant pressure is given by:
Qbc=nCPΔT=γPΔVγ−1Q_{bc} = nC_P\Delta T = \dfrac{\gamma P\Delta V}{\gamma - 1}
Substituting the values:
Qbc=1.67×2×105×(1.5×10−4−10−4)1.67−1Q_{bc} = \dfrac{1.67 \times 2 \times 10^5 \times (1.5 \times 10^{-4} - 10^{-4})}{1.67 - 1}
Qbc=1.67×2×105×0.5×10−40.67Q_{bc} = \dfrac{1.67 \times 2 \times 10^5 \times 0.5 \times 10^{-4}}{0.67}
Qbc=1.67×100.67=16.70.67≈24.9 JQ_{bc} = \dfrac{1.67 \times 10}{0.67} = \dfrac{16.7}{0.67} \approx 24.9 \text{ J}

The heat supplied in paths abab and bcbc are 14.9 J14.9 \text{ J} and 24.9 J24.9 \text{ J} respectively.

Answer: 14.9 J14.9 \text{ J}, 24.9 J24.9 \text{ J}
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