Question

A fixed mass 'm' of a gas is subjected to transformation of states from K to L to M to N and back to K as shown in the figure.

The succeding operation that enable this transformation of states are

• A. Heating, cooling, heating, cooling
• B. Cooling, heating, cooling, heating
• C. Heating, cooling, cooling, heating
• D. Cooling, heating, heating, cooling

Answer 1

The correct option is C Heating, cooling, cooling, heating

To reiterate the operations follow the path K, L. M, N. We simply need to use the ideal gas law here to get an idea what happens. The ideal gas law states that:

$PV=nRT$.

Since there is only a transformation of states number of moles (n) remains constant. Looking at these processes, in each of the steps either the pressure of the volume is constant. So using this law its pretty easy to figure out what happens..

Clearly - K to L would be heating since volume is increasing (P is constant). L to M is interesting, since P decreases keeping V constant. Now, this is possible only if cooling happens (i.e. T falls) . This is a direct consequence of the ideal gas law.
Similarly, in steps M - N cooling happens : P is constant, V decreases which means that T must fall. And lastly, N - K heating has to happen since V is constant, and P increases.