Question

In an adiabatic expansion of as gas, its temperature:

• A. always increase
• B. always diminishes
• C. remains constant
• D. none of these

Answer 1

The correct option is D none of these

In an adiabatic expansion of a gas, its temperature decreases.

From 1st law of thermodynamics,

$dU=dQ-dW$

For adiabatic process, $dQ=0$

Hence, $dU=-dW$

Gas gas expansion, $dW>0$ (positive)

Therefore, $dU$ is less than 0, and thus internal energy decreases.

This decrease in internal energy manifest itself as a decrease in temperature T. So, the temperature decreases in an adiabatic expansion of a gas.