Question

The temperature of the system decreases in an:

• A. Adiabatic compression
• B. Isothermal compression
• C. Isothermal expansion
• D. Adiabatic expansion

Answer 1

The correct option is D Adiabatic expansion

Work done in an adiabatic process is given as:
$w=△U$
$w=-P△V=n{C}_v△T$
In adiabatic explansion work is done by the system so $w=-ve$ as per sign convention. So,
$n{C}_v△T=-ive$
means $△T=-ive$
so,
final tempearture ($T_2$) is less than initial temperature ($T_1$).
hence, temperature decreases.
In adiabatic compression T increases and in isothermal processes, T remains same.