Cornell Notes: Thermodynamic Processes

Cue	Notes
What is constant in an isothermal process?	Temperature (T = const). For ideal gas: $\Delta U$ = 0, so Q = W = nRT ln( $V_{2}$ / $V_{1}$ ). Curve: rectangular hyperbola (PV = const).
What is zero in an adiabatic process?	Heat exchange (Q = 0). W = − $\Delta U$ = nCᵥ( $T_{1}$ − $T_{2}$ ). Curve: steeper hyperbola (PV^γ = const). Gas cools on expansion.
What is zero in an isochoric process?	Work (W = 0, since $\Delta V$ = 0). All heat goes to internal energy: Q = $\Delta U$ = nCᵥ $\Delta T$ . P/T = const. Vertical line on PV diagram.
What is constant in an isobaric process?	Pressure (P = const). W = P $\Delta V$ = nR $\Delta T$ . Q = nCₚ $\Delta T$ . V/T = const. Horizontal line on PV diagram.
Why is adiabatic curve steeper than isothermal?	Adiabatic: PV^γ = const (γ > 1). Isothermal: PV = const. The γ exponent makes adiabatic fall off faster with volume.
What does area under PV curve represent?	Work done by the gas. Positive for clockwise cycle (engine); negative for anticlockwise (refrigerator).