JEE AdvancedPhysicsHeat and ThermodynamicsNumerical+4 / −1
Consider one mole of helium gas enclosed in a container at initial pressure P1 and volume V1. It expands isothermally to volume 4V1. After this, the gas expands adiabatically and its volume becomes 32V1. The work done by the gas during isothermal and adiabatic expansion processes are Wiso and Wadia, respectively. If the ratio = f ln 2, then f is .
Numerical answer
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Correct answer: 1.77
- Given: one mole of helium gas.
For helium, being a monoatomic ideal gas,
We need the ratio
- Isothermal expansion from to .
For one mole of ideal gas, work done in isothermal expansion is Here , and initially , so
- State after isothermal expansion.
Since the process is isothermal, with So, Also, temperature remains .
- Adiabatic expansion from to .
For adiabatic process, Thus, So, Now, Hence,
- Work done in adiabatic expansion.
For adiabatic expansion of ideal gas, For one mole of monoatomic gas, Therefore, Using ,
- Take the ratio.
Comparing with we get
- Comparison with stored answer.
Stored correct answer = .
Our derived value is which rounds to , and to two decimal places may also be reported as depending on truncation.
So the stored answer is essentially consistent.
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