Question

Which of the following graphs correctly represent adiabatic expansion?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

$\Rightarrow$Option $\left(a\right)$ is rejected since $T_i=T_f=T_1$, so it represents the isothermal expansion.

In option $\left(c\right)$, initial and final temperatures are not same, apart from that curve is in a shape of hyperbola hence it represents adiabatic process. In an adiabatic process $(Q=0)$expansion occurs at the expense of internal energy of system
i.e $\Delta U=-W...\left(i\right)$
In case of expansion, from Eq$\left(i\right)$, $W\text{is}+ve\&\Delta U\text{is}-ve$
$\Rightarrow \Delta U=T_2-T_1$
Hence temperature of system decreases (i.e $T_1>T_2)$.
$\therefore \left(c\right)$option is correct.