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A real engine has an efficiency of 33%. The engine has a work output of 24 j per cycle (a) How much hear energy is extracted from the high temperature reservoir per cycle (A) 8 J (B) 16 J (C) 48 J (D)72 J (E) the question can be answered only if the engine is a carnot engine. (b) How much heat energy is discharged into the low temperature reservoir per cycle? (A) 8 J (B) 16 J (C) 48 J (D) 72 J (E) the question can be answered only if the engine is a carnot engine. (c) For this engine T L = 27ºC. What can be concluded about T H ? (A) T H = 450ºC (B)T H =177ºC. (C) T H > 177ºC. (D)T H (E) 177ºC H

A real engine has an efficiency of 33%. The engine has a work output of 24 j per cycle (a) How much hear energy is extracted from the high temperature reservoir per cycle      
(A) 8 J                  
(B) 16 J               
(C) 48 J                               
(D)72 J                                                         (E) the question can be answered only if the
engine is a carnot engine.     
(b) How much heat energy is discharged into the low temperature reservoir per cycle?                                                           
(A) 8 J  
(B) 16 J               
(C) 48 J               
(D) 72 J               
(E) the question can be answered only if the engine is a carnot engine.
(c) For this engine TL = 27ºC. What can be concluded about TH? 
(A) TH   = 450ºC              
(B)TH=177ºC.                                                                                                              
(C) TH > 177ºC.               
(D)TH
(E) 177ºC H

Grade:11

4 Answers

Aditi Chauhan
askIITians Faculty 396 Points
7 years ago
(a) The correct option is (D) 72 J.
The efficiency ε of a Carnot engine is defined as,
236-1968_1.PNG
236-1120_1.PNG
Urjita Sharma
21 Points
6 years ago
As the formula of efficiency is only applicable to Carnot engines and as this is a real engine the first two questions cannot be answered. Thus option E for both.If it were a Carnot`s engine, then TH would have been 177°C . Considering a Carnot`s engine having The as 177 C would give efficiency of 33% but as this is a real engine its efficiency must be less than 33%. Hence if it is 33% then it`s TH must be greater than 177°C.
Urjita Sharma
21 Points
6 years ago
The answer for first two can be given by the formula e= W/Qh1/3= 24/QhQh=72J1/3=1-Ql/QhQl= 48JPardon my previous answer was wrong.The third part is pretty much fine.
Urjita Sharma
21 Points
6 years ago
For the third part, if the efficiency is less than a Carnot`s engine, for a Carnot`s engine its The would be 177C e=W/Qh Qh proportional to Th hence e is inversely proportional to Th thus as e is less than will be more than 177C

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