# Heat Extracted and Delivered to Reservoirs in a Heat Engine

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1. May 13, 2016

### Willfrid Somogyi

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?

Last edited by a moderator: May 13, 2016
2. May 13, 2016

### Staff: Mentor

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?

3. May 13, 2016

### Willfrid Somogyi

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?

4. May 13, 2016

### Staff: Mentor

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.

5. May 13, 2016

### Willfrid Somogyi

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.

6. May 13, 2016

### Staff: Mentor

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: May 13, 2016
7. May 14, 2016

### Willfrid Somogyi

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 wont 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.

8. May 14, 2016

### Staff: Mentor

How do you define the efficiency of a heat engine?