Chapter 19: Problem 6
Your power company claims that electric heat is \(100 \%\) efficient. Discuss.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chapter 19: Problem 6
Your power company claims that electric heat is \(100 \%\) efficient. Discuss.
These are the key concepts you need to understand to accurately answer the question.
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Get started for freeA Carnot engine extracts \(890 \mathrm{J}\) from a \(550 \mathrm{K}\) reservoir during each cycle and rejects \(470 \mathrm{J}\) to a cooler reservoir. It operates at 22 cycles per second. Find (a) the work done during each cycle, (b) its efficiency, (c) the temperature of the cool reservoir, and (d) its mechanical power output.
An ideal gas undergoes a process that takes it from pressure \(p_{1}\) and volume \(V_{1}\) to \(p_{2}\) and \(V_{2},\) such that \(p_{1} V_{1}^{\gamma}=p_{2} V_{2}^{\gamma},\) where \(\gamma\) is the specific heat ratio. Find the entropy change if the process consists of constant-pressure and constant-volume segments. Why does your result make sense?
A shallow pond contains 94 Mg of water. In winter, it's entirely frozen. By how much does the entropy of the pond increase when the ice, already at \(0^{\circ} \mathrm{C},\) melts and then heats to its summer temperature of \(15^{\circ} \mathrm{C} ?\)
Use appropriate energy-flow diagrams to analyze the situation in Got It? \(19.2 ;\) that is, show that using a refrigerator to cool the lowtemperature reservoir can't increase the overall efficiency of a Carnot engine when the work input to the refrigerator is included.
A refrigerator maintains an interior temperature of \(4^{\circ} \mathrm{C}\) while its exhaust temperature is \(30^{\circ} \mathrm{C} .\) The refrigerator's insulation is imperfect, and heat leaks in at the rate of 340 W. Assuming the refrigerator is reversible, at what rate must it consume electrical energy to maintain a constant \(4^{\circ} \mathrm{C}\) interior?
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