Heat Extracted and Delivered to Reservoirs in a Heat Engine

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Homework Help Overview

The discussion revolves around a heat engine operating between two temperatures, specifically 500K and 300K, with a focus on calculating the heat extracted from the hot reservoir and the heat delivered to the cold reservoir. The problem also touches on the efficiency of the engine compared to a Carnot engine.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the efficiency of the heat engine and its relation to the Carnot efficiency. Questions are raised about the fractions of heat converted to work and released to the cold reservoir. Some participants express a lack of foundational knowledge regarding heat engines, prompting inquiries about the academic context and available resources.

Discussion Status

The discussion is ongoing, with participants seeking clarification on theoretical concepts related to heat engines. Some guidance has been offered regarding the forum's approach to learning, emphasizing the importance of self-discovery rather than providing complete answers. Participants are encouraged to share their academic context and resources they have consulted.

Contextual Notes

Some participants mention constraints such as a lack of prior instruction on the topic, limited access to textbooks, and difficulties in obtaining responses from their lecturer. The discussion reflects a shared challenge among peers regarding understanding the material.

Willfrid Somogyi
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NO TEMPLATE---MISPLACED HOMEWORK

So it seems like a pretty simple question, and in all likelihood it is, but my lecturer somehow managed to miss this bit in his lecture notes.

A heat engine operates between 500K and 300K with 20% of the efficiency of Carnot engine operating between the same temperatures. If the work done per cycle is 100 kJ, calculate:
(i) The heat extracted from the hot reservoir per cycle.
(ii) The heat delivered to the cold reservoir per cycle

Can anyone help?
 
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For a Carnot engine operating between these temperatures, what fraction of the heat received from the hot reservoir is released to the cold reservoir? What fraction is converted to work? What is the efficiency?
 
Chestermiller said:
For a Carnot engine operating between these temperatures, what fraction of the heat received from the hot reservoir is released to the cold reservoir? What fraction is converted to work? What is the efficiency?
Sorry, to be clear this isn't homework. This is simply a practice question I found elsewhere and I'd like a complete answer if that's possible?
 
Willfrid Somogyi said:
Sorry, to be clear this isn't homework. This is simply a practice question I found elsewhere and I'd like a complete answer if that's possible?
You'd like a complete answer, but that's not how we work here at Physics Forums. We help you get the answer yourself by asking you leading questions and giving you hints. If that's not the way you are willing to proceed, then have a nice day.
 
Well it's going to be a bit of an issue as I've never been taught it, as mentioned in the original post, so I have no knowledge of any of the theory, hence why I asked for a complete answer.
 
Willfrid Somogyi said:
Well it's going to be a bit of an issue as I've never been taught it, as mentioned in the original post, so I have no knowledge of any of the theory, hence why I asked for a complete answer.
Physics Forums is not structured as a venue for providing a complete tutorial on something like this. Maybe, someday, someone will write a Physics Forums Insights article on heat engines, but, as of now, no such article exists.

Tell us more about your situation. What is the academic course that this problem comes from? If heat engines were not covered in your course, are you still expected to be responsible for the material? What textbook are you using in your course, and what other textbooks or online sources have you consulted to develop background for solving this problem?
 
Last edited:
Chestermiller said:
Physics Forums is not structured as a venue for providing a complete tutorial on something like this. Maybe, someday, someone will write a Physics Forums Insights article on heat engines, but, as of now, no such article exists.

Tell us more about your situation. What is the academic course that this problem comes from? If heat engines were not covered in your course, are you still expected to be responsible for the material? What textbook are you using in your course, and what other textbooks or online sources have you consulted to develop background for solving this problem?

It's in the syllabus and a similar question came up in a past paper, I've tried emailing my lecturer but have had no response and being out of term time he won't be available at the University itself. I'm currently on a first year Physics course. I've tried looking in the usual places including this forum, HyperPhysics and a few other online teaching resources but none offered a clear explanation. I don't have access to a textbook as the recommend ones for my course are ~ £160 and I can't afford that. The university library isn't open at the moment or I'd use the textbook there and all my peers are having the same problem as myself.
 
How do you define the efficiency of a heat engine?
 

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