තාපගති විද්‍යාත්මක ක්‍රියාවලි — උ/පෙළ භෞතික විද්‍යාව

Thermodynamic Process A change in the state of a system (defined by pressure, volume, and temperature) from an initial equilibrium state to a final equilibrium state. Each process follows a specific path on a P-V diagram, and the work done, heat exchanged, and internal energy change depend on the path. For example, compressing a gas in a piston-cylinder assembly slowly (quasi-statically) allows the gas to remain in equilibrium throughout.

Isothermal Process A process occurring at constant temperature (ΔT = 0). For an ideal gas, internal energy depends only on temperature, so ΔU = 0. By the First Law (ΔU = Q – W), the heat added equals the work done by the gas. Real-world example: a gas expanding slowly in a cylinder immersed in a constant-temperature water bath, so heat flows in to keep temperature constant.