Question

Assertion : During an adiabatic process, heat energy is not exchanged between system and its surroundings.
Reason : The temperature of a gas increases when it undergoes an adiabatic expansion.

• A. If both assertion and reason are true and reason is a correct explanation of the assertion
• B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
• C. If the assertion is true but the reason is false
• D. If both the assertion and reason are false

Answer 1

Answer: (C)

In adiabatic process, no heat enters or leaves the system. The system is completely insulated from its surroundings. From first law of thermodynamics, change in internal energy,

$\Delta E=q-W=0-W=-W$.

Since the work is done at the expense of internal energy, therefore internal energy of the system decreases and hence temperature of the gas falls.