Question

During an adiabatic expansion, the increase in volume is associated with which of the following possibilities $w.r.t$. pressure and temperature?

Pressure		Temperature
a	increase	increase
b	decrease	decrease
c	increase	decrease
d	decrease	increase

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (B)

According to first law of thermodynamics
$\Delta Q=\Delta U+\Delta W$
For an adiabatic process
$\Delta Q=0$
$\therefore \Delta U=-W$
In adiabatic process
$p \propto \frac{1}{V^{\gamma}}$ and $T \propto \frac{1}{V^{\gamma-1}}$
$\gamma>1$, because volume increases.
Then, $p$ and $T$ will decrease.