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Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 Problem 6 Problem 7 Problem 8 Problem 9 Problem 10 Problem 11 Problem 12 Problem 13 Problem 14 Problem 15 Problem 16 Problem 17 Problem 18 Problem 19 Problem 20 Problem 21 Problem 22 Problem 23 Problem 24 Problem 25 Problem 26 Problem 27 Problem 28 Problem 29 Problem 30 Problem 31 Problem 32 Problem 33 Problem 34 Problem 35 Problem 36 Problem 37 Problem 38 Problem 39 Problem 40 Problem 41 Problem 42 Problem 43 Problem 44 Problem 45 Problem 46 Problem 47 Problem 48 Problem 49 Problem 50 Problem 51 Problem 52 Problem 53 Problem 54 Problem 55 Problem 56 Problem 57 Problem 58 Problem 59 Problem 60 Problem 61

Problem 34 Hard Difficulty

Would you be willing to financially back an inventor who is marketing a device that she claims has 25 kJ of heat transfer at 600 K, has heat transfer to the environment at 300 K, and does 12 kJ of work? Explain your answer.

Answer

The actual efficiency is 96$\%$ of the Carnot efficiency, which is much higher than the best-
ever achieved of about $70 \%,$ so her scheme is likely to be fraudulent.

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Physics 101 Mechanics

College Physics for AP® Courses

Chapter 15

Thermodynamics

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The First Law of Thermodynamics

The Second Law of Thermodynamics

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Problem 16
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Video Transcript

his problem 34 Chapter 15 and were asked, Would you be willing to financially back an investor who is marketing a device that she claims has 25 killer jewels of heat transfer at 600 degrees? Kelvin has he transferred to the environment at 300 Degrees column and does 12 killer jewels of work? We're supposed to explain her answer. And so here is tthe E formula for the efficiency of a perfect heat engine, where efficiency is equal to one minus the temperature of the cold reservoir over the temperature of the hot reservoir on. Then we also have the heat transfer. Uh, which is Q C is equal to qh minus w. And so, using this equation here, we can go ahead and find our heat transfer. And so do you see? It's gonna be equal to substitute 25 killer Jules minus 12. Killer Jules on this is gonna be equal to 13 killer Jules on. We can go ahead and calculate the actual efficiency using this equation here, where efficiency is equal to one minus to see over. Qh on. So we have this value so we can go ahead and substitute. Listen so our efficiency is gonna be equal to one minus 13. Killer Jules over 25 killed Jules on. This is gonna be equal to 0.48 which is our efficiency on. Then we can go ahead and solve for our other efficiency. So this is gonna be NC is equal to one minus 300 degrees Kelvin over 600. Did you discover I was just gonna be equal to 0.5 on DSO For an actual Karna engine? We actually have an efficiency of 96% which is much higher than the best ever achieved, which is about 70%. Um, so because of these values, you can actually know that this scheme is gonna be fraudulent.

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