Thermodynamic Processes — A/L Physics

What must I remember about Thermodynamic Processes?

• First Law of Thermodynamics: Conservation of energy applied to thermodynamic systems: ΔQ = ΔU + ΔW, where ΔQ is heat supplied to system, ΔU is change in internal energy, and ΔW is work done by system (ΔW = P ΔV for constant pressure).
• Internal Energy of Ideal Gas: Depends purely on absolute temperature T: ΔU = n C_v ΔT; for a complete cyclic process, ΔU_cycle = 0, so Q_net = W_net.
• Standard Thermodynamic Processes: Isothermal (constant T, ΔU = 0, Q = W = nRT ln(V2/V1)); Isobaric (constant P, W = P(V2 - V1), Q = n C_p ΔT); Isochoric/Isometric (constant V, W = 0, Q = ΔU = n C_v ΔT); Adiabatic (zero heat exchange Q = 0, W = -ΔU, P V^γ = Constant).
• Molar Heat Capacities: Mayer's Relation: C_p - C_v = R; Ratio of specific heats γ = C_p / C_v > 1 (γ = 5/3 for monatomic, γ = 7/5 for diatomic gas).

Test yourself (1 minute)

1. P-V Indicator Diagrams

   Work done during any process equals the area under the curve on a P-V diagram; for a cyclic process, net work done equals enclosed area (positive for clockwise/engine cycle, negative for anticlockwise/refrigerator).

2. Adiabatic vs Isothermal Slopes

   The slope of an adiabatic curve on a P-V diagram is steeper than an isothermal curve by a factor of γ: (dP/dV)_adiab = γ (dP/dV)_isotherm.

3. Second Law of Thermodynamics (Kelvin-Planck & Clausius)

   Heat cannot spontaneously flow from cold to hot body without external work; No heat engine can be 100% efficient (Carnot efficiency η = 1 - T_cold / T_hot).

Practise Thermodynamic Processes questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 4: Thermal Physics

What should I study first?

Next in the syllabus

Where does Thermodynamic Processes fit in the syllabus?

Unit 4.8 · Year 1 · Term 2