• id: JTHERM-01-N06
• title: Isothermal Process — Constant Temperature
• tags: isothermal, constant-T, boyle

Condition: temperature constant, $\Delta T = 0$, so $\Delta U = 0$. First Law: $Q = W$. The equation PV = nRT = constant gives Boyle's law: $P_1V_1 = P_2V_2$. Work: $W = nRT\ln(V_2/V_1)$. On P-V diagram: rectangular hyperbola. Isothermal requires slow process (quasi-static) and thermal contact with a reservoir. The system absorbs heat from the reservoir to maintain constant T during expansion. For an isothermal process, specific heat is effectively infinite: $C_T = Q/(n\Delta T) = Q/0 \to \infty$.