Ch1b09Lecture12

# Ch1b09Lecture12 - MidTerm Review 7 p.m. Thursday evening...

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1 MidTerm Review 7 p.m. Thursday evening Sorry we can’t have two review sessions Get a friend to videotape

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2 The Carnot Cycle P Volume A B C D -work net Efficiency = work out /q in isothermal isothermal a d i b t c How efficient can this engine be? We need to calculate how much work we can get out of this system for a given amount of heat input
3 The Carnot Cycle Volume A B C D -work net Efficiency = work out /q in isothermal isothermal a d i b t c How efficient can this engine be? Clicker Question The adiabatic processes must be considered when calculating the efficiency True False

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4 The Carnot Cycle P Volume A B C D -work net Work out the various pathways first Isothermal Temp - T H How efficient? A Æ B = = A B H AB AB V V nRT q w ln
5 The Carnot Cycle P Volume A B C D -work net Work out the various pathways first Isothermal Temp - T H How efficient? B Æ C ( ) H L V BC BC T T nc w U = = q=0 Adiabatic T = T H Æ T L

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6 The Carnot Cycle P Volume A B C D -work net Work out the various pathways first Isothermal Temp - T H How efficient? Skipping to D Æ A ( ) L H V DA DA T T nc w U = = q=0 Adiabatic T = T L Æ T H ( ) DA H L V BC BC w T T nc w E = = = Note that this exactly cancels out w BC
7 The Carnot Cycle P Volume A B C D -work net pathway C Æ D Isothermal Temp - T L How efficient? = = C D L CD CD V V nRT q w ln Since w BC = -w DA , all work is along pathways A Æ B and C Æ D Thus , w BC +w DA = 0 i.e. all work is along pathways A Æ B and C Æ D

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8 The Carnot Cycle P Volume A B C D -work net How efficient? + = D C L A B H total V V nRT V V nRT w ln ln Why don’t we worry about w BC +w DA contributions? = = C D L CD CD V V nRT q w ln = = A B H AB AB V V nRT q w ln