Question

An ideal gas goes through a reversible cycle $a\to b\to c$ $\to d$ has the V-T diagram shown below. Process $d\to a$ and $b\to c$ 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 $a\to b$ and $c\to d,V\alpha T$, that is pressure is constant.
$PV=nRT\Rightarrow \frac{V}{T}=$ Slope
$=\frac{nR}{P}\Rightarrow$ Slope $\propto \frac{1}{P}$
Since sloped $cd>$ slope ab, $P_{\text{cd }}<P_{\text{ab }}$
For adiabatic process $d\to a,T{V}^{r-1}=$ Constant
As $T\uparrow ,V\downarrow$ so $P$ has to increase.