2. These questions explore moving boundary work and polytropic processes in closed systems: (a) Explain the concept of "moving boundary work" (Wb) in a closed system.
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Step 1: Define the system and boundary In a closed system, the mass remains constant, but the volume can change due to the movement of the system boundary, such as a piston or a diaphragm. Show more…
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A closed system consists of an ideal gas with mass $m$ and constant specific heat ratio $k$. If kinetic and potential energy changes are negligible, (a) show that for any adiabatic process the work is $$ W=\frac{m R\left(T_{2}-T_{1}\right)}{1-k} $$ (b) show that an adiabatic polytropic process in which work is done only at a moving boundary is described by $p V^{k}=$ constant.
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For the expression pdv to represent the work, which of the following conditions should apply? (a) The system is a closed one and the process takes place in a non-flow system (b) The process is non-quasi-static (c) The boundary of the system should not move in order for work to be transferred (d) If the system is an open one, it should be non-reversible.
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Problem 1: Answer the following concept-related questions: (a) When is the energy crossing the boundaries of a closed system heat and when is it work? (b) For a cycle, is the net work necessarily zero? For what kind of systems will this be the case? (c) If the pressure of a substance is increased during a boiling process, will the temperature also increase or will it remain constant? Why? (d) When pressure and the specific volume of a pure substance (e.g., water) are given, the state of the pure substance can always be determined. Is it true or false? Why?
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