Concepts Of Physics MCQ Edition [Volume 2]
- Exam
- Concepts Of Physics MCQ Edition [Volume 2]
- Subject
- Physics
- Chapter
- Laws of Thermodynamics
Concepts Of Physics MCQ Edition [Volume 2] · Physics · Laws of Thermodynamics
A cylindrical tube of volume V having adiabatic walls contains an...
A cylindrical tube of volume having adiabatic walls contains an ideal gas. The internal energy of this ideal gas is given by . A fixed diathermic wall divides the tube into two equal parts. Initially, the pressure and temperature are on the left side and on the right side. The system is allowed sufficient time for the temperatures on both sides to become equal. Find the final pressures on the left and right sides respectively. (Let )


Options
- A and
- B and
- C and
- D and
Correct answer
C. and
Step-by-step solution
Let the volume of each part be .
The number of moles of gas in the left part is:
The number of moles of gas in the right part is:
Since the outer walls are adiabatic and the total volume is constant, the total internal energy of the system remains conserved. Let the final common temperature be .
Solving for :
Substituting the expressions for and :
n_1 + n_2 = \dfrac{V_0}{R} \left( \dfrac{p_1}{T_1} + \dfrac{p_2}{T_2} \right) = \dfrac{V_0}{R} \left(\dfrac{p_1 T_2 + p_2 T_1}{T_1 T_2} \right)
Therefore, the final temperature is:
\dfrac{\dfrac{V_0}{R}(p_1 + p_2)}{\dfrac{V_0}{R} \left( \dfrac{p_1 T_2 + p_2 T_1}{T_1 T_2} \right)} = \dfrac{(p_1 + p_2) T_1 T_2}{p_1 T_2 + p_2 T_1}
Given , we can write:
\dfrac{(p_1 + p_2) T_1 T_2}{\lambda}
Now, applying the ideal gas law to find the final pressure on the left side () and right side (), keeping in mind that the volume of each part remains :
For the left side:
\dfrac{p_1}{T_1} = \dfrac{p_{1f}}{T_f} \Rightarrow\dfrac{p_1}{T_1}\dfrac{p_1}{T_1} \left[ \dfrac{(p_1 + p_2) T_1 T_2}{\lambda} \right] = \dfrac{p_1 T_2 (p_1 + p_2)}{\lambda}
For the right side:
\dfrac{p_2}{T_2} = \dfrac{p_{2f}}{T_f} \Rightarrow\dfrac{p_2}{T_2}\dfrac{p_2}{T_2} \left[ \dfrac{(p_1 + p_2) T_1 T_2}{\lambda} \right] = \dfrac{p_2 T_1 (p_1 + p_2)}{\lambda}
Answer: \dfrac{p_1 T_2 (p_1 + p_2)}{\lambda} and \dfrac{p_2 T_1 (p_1 + p_2)}{\lambda}
The number of moles of gas in the left part is:
The number of moles of gas in the right part is:
Since the outer walls are adiabatic and the total volume is constant, the total internal energy of the system remains conserved. Let the final common temperature be .
Solving for :
Substituting the expressions for and :
n_1 + n_2 = \dfrac{V_0}{R} \left( \dfrac{p_1}{T_1} + \dfrac{p_2}{T_2} \right) = \dfrac{V_0}{R} \left(\dfrac{p_1 T_2 + p_2 T_1}{T_1 T_2} \right)
Therefore, the final temperature is:
\dfrac{\dfrac{V_0}{R}(p_1 + p_2)}{\dfrac{V_0}{R} \left( \dfrac{p_1 T_2 + p_2 T_1}{T_1 T_2} \right)} = \dfrac{(p_1 + p_2) T_1 T_2}{p_1 T_2 + p_2 T_1}
Given , we can write:
\dfrac{(p_1 + p_2) T_1 T_2}{\lambda}
Now, applying the ideal gas law to find the final pressure on the left side () and right side (), keeping in mind that the volume of each part remains :
For the left side:
\dfrac{p_1}{T_1} = \dfrac{p_{1f}}{T_f} \Rightarrow\dfrac{p_1}{T_1}\dfrac{p_1}{T_1} \left[ \dfrac{(p_1 + p_2) T_1 T_2}{\lambda} \right] = \dfrac{p_1 T_2 (p_1 + p_2)}{\lambda}
For the right side:
\dfrac{p_2}{T_2} = \dfrac{p_{2f}}{T_f} \Rightarrow\dfrac{p_2}{T_2}\dfrac{p_2}{T_2} \left[ \dfrac{(p_1 + p_2) T_1 T_2}{\lambda} \right] = \dfrac{p_2 T_1 (p_1 + p_2)}{\lambda}
Answer: \dfrac{p_1 T_2 (p_1 + p_2)}{\lambda} and \dfrac{p_2 T_1 (p_1 + p_2)}{\lambda}