Question

Two samples A and B are initially kept in the same state. Sample A is expanded through an adiabatic process and the sample B through an isothermal process. The final volumes of the samples are the same. The final pressures in A and B are pA and pB respectively.
(a) pA > pB
(b) pA = pB
(c) pA < pB
(d) The relation between pA and pB cannot be deduced.

Answer 1

The correct answer is (c), which is pA < pB.

Explanation:

• Samples A and B have the initial states denoted as i. These samples have the final states as f and f’, respectively.
• Let us consider that the final volumes of both the samples is Vo. Using an adiabatic process, sample A is expanded and, in the p-V diagram, its curve becomes sharper than that of sample B, which is extended via an isothermal process.
• So, it is concluded from the p-V diagram that pA < pB.