Question

A sample of gas was first compressed from V1 to V2 at a constant pressure of P1. The sample was then cooled so that the pressure went from P1 to P2 while the volume remained constant at V2. Finally the sample was allowed to expand from V2 back to V1 while the pressure increased from P2 back to P1 as shown in the diagram. Which of the following statements is correct?

(A) The area A represents the energy that is lost by the gas in this cycle.

(B) The area A + B represents the energy gained by the gas in this cycle.

(C) The area A + C represents the energy gained by the gas in this cycle.

(D) The area B + D represents the energy gained by the gas in this cycle.

(E) There was no energy lost or gained by the gas in this cycle.

Answer 1

Correct option (A) The area A represents the energy that is lost by the gas in this cycle.

Explanation:

The “energy” lost or gained would be the sum of the work done on the gas and the net heat added to the gas, which is the change in internal energy of the gas. Since the gas returns to its original state, ∆U = 0.