An ideal gas expands from volume V₁ to V₂ . This may be achieved by either of three processes: i

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11.Thermodynamics

normal

An ideal gas expands from volume $V_1$ to $V_2$. This may be achieved by either of the three processes: isobaric, isothermal and adiabatic. Let $\Delta U$ be the change in internal energy of the gas, $Q$ be the quantity of heat added to the system and $W$ be the work done by the system on the gas. Identify which of the following statements is false for $\Delta U$?

$\Delta U$ is least under adiabatic process.

$\Delta U$ is greatest under adiabatic process.

$\Delta U$ is greatest under the isobaric process.

$\Delta U$ in isothermal process lies in-between the values obtained under isobaric and adiabatic processes.

We know that, $\Delta U \propto \Delta T$

For isotherm, $\Delta T=0 \Rightarrow \Delta U=0$

For adiabat, $\Delta Q=0 \Rightarrow \Delta U=-\Delta W<0$

For isobar, $\Delta V \propto \Delta T \Rightarrow \Delta T>0 \Rightarrow \Delta U>0$

Let the internal energy change be $\Delta U_{1}, \Delta U_{2}, \Delta U_{3}$ for the isotherm, adiabat, isobar respectively.

Then $\Delta U_{3}>\Delta U_{1}>\Delta U_{2}$

Thus option $b$ is only false

Standard 11

Physics

easy

hard

medium

(AIEEE-2009)

medium

(AIPMT-1992)

medium