11/19/2012PHY 113 A Fall Lecture 321 PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 32: Chapter 22: Heat engines 1.Thermodynamic cycles; work and heat efficiency 2.Carnot cycle 3.Otto cycle; diesel cycle 4.Note – in this class, we will not focus on entropy and the second law of thermodynamics

11/19/2012 PHY 113 A Fall Lecture 322

11/19/2012PHY 113 A Fall Lecture 323 Thermodynamic cycles for designing ideal engines and heat pumps P (1.013 x 10 5 ) Pa ViVi VfVf PiPi PfPf A BC D Engine process:

11/19/2012PHY 113 A Fall Lecture 324 P (1.013 x 10 5 ) Pa ViVi VfVf PiPi PfPf A BC D Examples process by an ideal gas: ABABBCBCCDCDDADA Q W0-P f (V f -V i )0P i (V f -V i )  E int

11/19/2012PHY 113 A Fall Lecture 325 Example from homework

11/19/2012PHY 113 A Fall Lecture 326 Most efficient thermodynamic cycle -- Carnot Sadi Carnot

11/19/2012PHY 113 A Fall Lecture 327 Carnot cycle: A  B Isothermal at T h B  C Adiabatic C  D Isothermal at T c D  A Adiabatic

11/19/2012PHY 113 A Fall Lecture 328 iclicker exercise: We discussed the efficiency of an engine as Is this result A.Special to the Carnot cycle B.General to all ideal thermodynamic cycles iclicker exercise: We discussed the efficiency of an engine running with hot and cold reservoirs as Is this result A.Special to the Carnot cycle B.General to all ideal thermodynamic cycles

11/19/2012PHY 113 A Fall Lecture 329

11/19/2012PHY 113 A Fall Lecture 3210 iclicker exercise: Why should we care about the Carnot cycle? A.We shouldn’t B.It approximately models some heating and cooling technologies C.It provides insight into another thermodynamic variable -- entropy

11/19/2012PHY 113 A Fall Lecture 3211 The Otto cycle

11/19/2012PHY 113 A Fall Lecture 3212 The Diesel cycle

11/19/2012PHY 113 A Fall Lecture 3213

11/19/2012PHY 113 A Fall Lecture 3214 Engine vs heating/cooling designs