Thermodynamics

JEE Main level, single correct, medium

159 of 190

Question 159 of 190

An ideal gas goes through a reversible cycle a→b→c→da\rightarrow b\rightarrow c\rightarrow d has the V - T diagram shown below. Process d→aandb→cd\rightarrow aandb\rightarrow c are adiabatic.



The corresponding P - V diagram for the process is (all figures are schematic and not drawn to scale) :

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Answer: (A)

Is an adiabatic process

TVγ−1=const⇒VT1γ−1=constT{V}^{\gamma -1}=const\Rightarrow V{T}^{\dfrac{1}{\gamma -1}}=const

⇒\Rightarrow as T increase V decreases at non-uniform rate

In process
a→ba\rightarrow b P = constant as V∝TV\propto T

In process
c→dc\rightarrow d P′={P}^{'}= constant s V∝TV\propto T

But since slope of V - T graph
∝1P\propto \dfrac{1}{P}

since slope of ab < slope of cd


⇒Pab>Pcd\Rightarrow {P}_{ab}\gt {P}_{cd}

Also in adiabatic process
d→ad\rightarrow a as T is increasing V in decreasing

⇒\Rightarrow P is increasing, so P - V diagram is as below

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