Carnot Engine Question: Efficiency & Work/Heat Rejected

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Discussion Overview

The discussion revolves around a homework problem involving a Carnot heat engine, specifically focusing on calculating its efficiency, work done, and heat rejected based on given temperatures and absorbed heat. The scope includes theoretical understanding and application of thermodynamic principles.

Discussion Character

  • Homework-related
  • Technical explanation

Main Points Raised

  • The efficiency of the Carnot engine is calculated using the formula e = (T2-T1)/T2, leading to a result of approximately 0.6666.
  • The participant calculates the work done as 1600 J and the heat rejected as 800 J based on the total energy absorbed from the high-temperature reservoir.
  • Some participants express affirmation of the calculations, suggesting that the reasoning is sound and indicating an understanding of the material.

Areas of Agreement / Disagreement

Participants generally agree with the calculations presented, with no significant disagreement noted in the responses.

Contextual Notes

The discussion does not address potential limitations or assumptions in the calculations, such as the ideal nature of the Carnot engine or the implications of real-world factors.

Who May Find This Useful

Students studying thermodynamics, particularly those learning about heat engines and efficiency calculations.

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Homework Statement



A Carnot heat engine absorbs heat form a high-temp reservoir at 1200K and concerts some of it into useful work and rejects the rest to a low-temp reservoir at 400K. A) What is the efficiency of the engine? b) If the engine absorbs 2400J per cycle from the high-temp reservoir at 1200K, what is the amount of work done, and how much heat is rejected to the low-temp reservoir at 400K?

Homework Equations



A) e = (T2-T1)/T2
ΔU=Q-W

The Attempt at a Solution



For part a, I got (1200-400)/1200= 0.6666...

For part b, my logic is that Total energy = work + heat rejected, based on ΔU formula above.
Therefore, work done should be 2400J*0.66 = 1600 J and heat rejected should be the rest, aka 2400*0.33 = 800J.

These answers seems to easy, especially for part b. Am I doing something wrong?
 
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Everything is fine, nothing to worry...
Regards
 
Well done. Sometimes physics is easy - with that reasoning it sounds like you have understood the material.
 
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Simon Bridge said:
Well done. Sometimes physics is easy - with that reasoning it sounds like you have understood the material.

Thanks for the confirmation.
 

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