Q.Derive the expression for the work done in a volume change in a thermodynamic system.

A PV diagram plots a gas's pressure against its volume to represent its thermodynamic state and the process it undergoes; the area under the curve equals the work done.

Every equilibrium state of a fixed quantity of gas can be represented as a single point on a graph with volume V along the x-axis and pressure P along the y-axis -- this is called a PV diagram (or indicator diagram).

As a gas undergoes a thermodynamic process (isothermal, isobaric, isochoric, adiabatic, or a full cycle as in a heat engine), the state point moves along a path (curve) on this diagram, showing exactly how P and V change together at every instant of the process.

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A P-V (pressure-volume) diagram graphs a gas's pressure against its volume during a process; the area under the curve represents the work done.

A P-V diagram is a graphical representation of the state of a gas (or any thermodynamic system) as it changes, with pressure P plotted on the vertical axis and volume V plotted on the horizontal axis.

Each point on the diagram represents a particular state (P, V) of the gas. As the gas undergoes a process (e.g. isothermal, isobaric, isochoric, or adiabatic), the state traces out a curve on the diagram.

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