2. AP Physics Chapter 15 The Laws of Thermodynamics Thermodynamics is the study of processes in which energy is transferred as heat and as work. A system is an object or set of objects to be considered. A closed system is where no mass enters or leaves a system. Open systems can lose or gain mass to the environment. An isolated system is a closed system where no energy crosses the system boundary.

3. 15-1 The First Law of Thermodynamics D U=Q – W The first law of thermodynamics is a statement of the conservation of energy law. See Example 15-1 p444

4. 15-2 First Law of Thermodynmics Applied to Some Simple Systems An isothermal process that is conducted with a constant temperature. Isotherms are lines of equal temperature… see page 445. A heat reservoir is a location of heat so large that it provides a isothermal environment. Adiabatic processes allow no heat energy to flow into or out of the system.

5. 15-2 (cont’d) An isobaric process is one in which pressure is kept constant. An Isochoric or isovolumetric process is one in which volume is held constant. See Conceptual Examples 15-2 and 15-3 p447. See Example 15-4, 15-5, and 15-6 p448.

6. 15-3 Human metabolism… the 1 st Law Metabolism is the name given to the energy producing and using reactions in living things. D U=Q – W See Example 15-7

7. The 2 nd Law of Thermodynamics …Heat flows from a hot object to a cold object; heat will not flow spontaneously from a cold object to a hot object. A heat engine is any device that changes thermal energy into mechanical work.

8. 15-5 Heat Engines Q H =W + Q L …where Q H is the heat input, W is work, and Q L is heat exhausted… all positive in value. (See diagram p 451) Temperature difference is required to run an engine. Effieciency… e=W/Q H =(Q H -Q L )/Q H = 1-(Q L /Q H ) See Example 15-8 p453

9. 15-5 (cont’d) Sadi Carnot (1796-1832) examined the ideal engine, now called a Carnot engine…the process of heat addition and exhaust were done reversibly, so that the process was considered a series of equilibrium states… real processes are actually irreversible. e ideal = (T H -T L )/T H = 1- (T L /T H ) See Example 15-9 p 454

10. HOMEWORK… P471 pr#1-3, 5-8, 14-16, 17-20 due next BOP