Question

A gas undergoes a cyclic process as shown in the $P-V$ diagram. For one complete cycle, choose the correct option among the following.

• A. Change in internal energy = 0, heat supplied < 0
• B. Change in internal energy = 0, heat supplied > 0
• C. Change in internal energy > 0, heat supplied < 0
• D. Change in internal energy < 0, heat supplied > 0

Answer 1

The correct option is A Change in internal energy = 0, heat supplied < 0

After one complete cycle, initial and final states of the gas are same
$\therefore$ Change in internal energy $\Delta U=0$
Hence, options (c) and (d) are wrong.

From the given $P-V$ graph, we know that the given cyclic process is anticlockwise.
$\therefore$Work done in one complete cycle is negative ($W<0$)
From the first law of thermodynamics, $\Delta Q=\Delta U+W=W$
So, we can conclude that heat supplied will also be negative.
i.e. heat supplied $\left(\Delta Q\right)<0$.
Thus, option (a) is the correct answer.