Question

An ideal gas goes through a reversible cycle $a \rightarrow b \rightarrow c$ $\rightarrow d$ has the V-T diagram shown below. Process $d \rightarrow a$ and $b \rightarrow c$ are adiabatic.
The corresponding $P - V$ diagram for the process is (all figures are schematic and not drawn to scale) :

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

In processes $a \rightarrow b$ and $c \rightarrow d , V \alpha T$, that is pressure is constant.
$P V=n R T \Rightarrow \frac{V}{T}=$ Slope
$=\frac{n R}{P} \Rightarrow $ Slope $\propto \frac{1}{P}$
Since sloped $c d>$ slope ab, $P_{\text {cd }}< P_{\text {ab }}$
For adiabatic process $d \rightarrow a , T V^{r-1}=$ Constant
As $T \uparrow, V \downarrow$ so $P$ has to increase.