Conceptual thermodynamics question

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SUMMARY

The forum discussion centers on understanding the differences between various types of heat engines, specifically in the context of Carnot engines. The user queries the nature of questions 16, 17, and 18 from a practice set, noting that all options lead to the conclusion that the engines are "a hoax" due to thermal efficiencies being less than 1. The user expresses confusion regarding the concept of reversibility in Carnot engines, which are ideally designed to avoid irreversible processes. The discussion emphasizes the importance of grasping the fundamental principles of thermodynamics to accurately interpret these questions.

PREREQUISITES
  • Understanding of Carnot heat engines and their theoretical foundations.
  • Familiarity with the concept of thermal efficiency in thermodynamic cycles.
  • Knowledge of reversible and irreversible processes in thermodynamics.
  • Basic grasp of heat transfer between reservoirs.
NEXT STEPS
  • Study the principles of Carnot efficiency and its implications on real-world heat engines.
  • Explore the differences between reversible and irreversible thermodynamic processes.
  • Investigate the concept of thermal efficiency and how it is calculated for various heat engines.
  • Review practice problems related to heat engines to reinforce understanding of these concepts.
USEFUL FOR

Students of thermodynamics, physics educators, and anyone seeking to deepen their understanding of heat engine efficiency and the principles governing thermodynamic cycles.

kuahji
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http://wps.prenhall.com/esm_giancoli_physicsppa_6/0,8713,1115091-,00.html (under practice questions)

On questions 16,17, & 18 I'm trying to figure what is the difference between them (Clearly Tc is different, but how does that change the problem?). The question asks
The heat engine shown above is

a) a reversible (Carnot) heat engine.
b) an irreversible (Carnot) heat engine.
c) a hoax.
d) none of the above.

I'm guessing I just don't understand the concepts, as I thought a Carnot engine was suppose to avoid irreversible processes, like an idealization. Anyway, the answer to 17 & 18 are "a hoax." They all seem to have thermal efficiencies of less than 1, so how should I look at these questions?
 
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Hi kuahji,

kuahji said:
http://wps.prenhall.com/esm_giancoli_physicsppa_6/0,8713,1115091-,00.html (under practice questions)

On questions 16,17, & 18 I'm trying to figure what is the difference between them (Clearly Tc is different, but how does that change the problem?). The question asks
The heat engine shown above is

a) a reversible (Carnot) heat engine.
b) an irreversible (Carnot) heat engine.
c) a hoax.
d) none of the above.

I'm guessing I just don't understand the concepts, as I thought a Carnot engine was suppose to avoid irreversible processes, like an idealization. Anyway, the answer to 17 & 18 are "a hoax." They all seem to have thermal efficiencies of less than 1, so how should I look at these questions?


For a heat engine operating between two heat reservoirs, what is the maximum efficiency possible?
 

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