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# Thermodynamics ## 1st Law of Thermodynamics $\Delta U = Q - W$ Where: * $\Delta U$ = Change in internal energy * $Q$ = Heat added to the system * $W$ = Work done by the system **Note:** These variables MUST have proper sign conventions * $Q > 0$ Heat added to the system * $W > 0$ Wor...

# Thermodynamics ## 1st Law of Thermodynamics $\Delta U = Q - W$ Where: * $\Delta U$ = Change in internal energy * $Q$ = Heat added to the system * $W$ = Work done by the system **Note:** These variables MUST have proper sign conventions * $Q > 0$ Heat added to the system * $W > 0$ Work done by the system ### Types of Thermodynamic Processes #### Isobaric * Constant Pressure * $W = P\Delta V$ * $\Delta U = Q - P\Delta V$ #### Isochoric * Constant Volume * $W = 0$ * $\Delta U = Q$ #### Isothermal * Constant Temperature * $\Delta U = 0$ * $Q = W$ #### Adiabatic * No Heat Exchange * $Q = 0$ * $\Delta U = -W$ ## 2nd Law of Thermodynamics ### Entropy * Measure of disorder * $\Delta S = \frac{Q}{T}$ * 2nd Law: the entropy of an isolated system can only increase ### Heat Engines * Convert heat into mechanical work * $W = Q_H - Q_C$ * Efficiency: $e = \frac{W}{Q_H} = \frac{Q_H - Q_C}{Q_H}$ ### Carnot Engine * Theoretical engine with maximum possible efficiency * $e_{max} = \frac{T_H - T_C}{T_H}$ * All steps are reversible ### Heat Pumps / Refrigerators * Use work to transfer heat from cold to hot * Coefficient of Performance: $COP = \frac{Q_C}{W}$