The pV diagram in (Figure 1) shows the cycle followed by the gas in an ideal-gas refrigerator whose coefficient of performance is 1.5. The work done by the system during two adiabatic processes is shown. Figure P 4 Adiabats 1 of 1 > W₁ = -119 J W, = 79 J V ▼ ✓ Correct Part F What is Win for one cycle of this heat engine? Express your answer with the appropriate units. ►View Available Hint(s) Win = 119 μÅ Submit Previous Answers Request Answer Part G Complete previous part(s) J X Incorrect; Try Again; One attempt remaining Part H Complete previous part(s) Provide Feedback ?

The pV diagram in (Figure 1) shows the cycle followed by the gas in an ideal-gas refrigerator whose coefficient of performance is 1.5. The work done by the system during two adiabatic processes is shown. Figure P 4 Adiabats 1 of 1 > W₁ = -119 J W, = 79 J V ▼ ✓ Correct Part F What is Win for one cycle of this heat engine? Express your answer with the appropriate units. ►View Available Hint(s) Win = 119 μÅ Submit Previous Answers Request Answer Part G Complete previous part(s) J X Incorrect; Try Again; One attempt remaining Part H Complete previous part(s) Provide Feedback ?

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter3: The First Law Of Thermodynamics

Section: Chapter Questions

Problem 79AP: Consider the process shown below. During steps AB and BC, 3600 J and 2400 J of heat, respectively,...

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An ideal gas expands isothermally along AB and does 700 J of work (see below). (a) How much heat does the gas exchange along AB? (b) The gas then expands adiabatically along BC and does 400 J of work. When the gas returns to A along CA, it exhausts 100 J of heat to its surroundings. How much work is done on the gas along this path?
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Consider the process shown below. During steps AB and BC, 3600 J and 2400 J of heat, respectively, are added to the system. (a) Find the work done in each of the processes AB, BC, AD, and DC. (b) Find the internal energy change in processes AB and BC. (c) Find the internal energy difference between states C and A (d) Find the total heat added in the ADC process. (e) From the information given, can you find the heat added in process AD? Why or why not?
Steam locomotives have an efficiency of 17.0% and operate with a hot steam temperature of 425C. (a) What would the cold reservoir temperature be if this were a Carnot engine? (b) What would the maximum eficiency of this steam engine be if its cold reservoir temperature were 150C ?
Consider the processes shown below. In the processes AB and BC, 3600 J and 2400 J of heat are added to the system, respectively. (a) Find the work done in each of the processes AB, BC, AD, and DC. (b) Find the internal energy change in processes AB and BC. (c) Find the internal energy difference between states C and A. (d) Find the total heat added in the ADC process. (e) From the information give, can you find the heat added in process AD? Why or why not?
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The gasoline internal combustion engine operates in a cycle consisting of six parts. Four of these parts involve, among other things, friction, heat exchange through finite temperature differences, and accelerations of the piston; it is irreversible. Nevertheless, it is represented by the ideal reversible Otto cycle, which is illustrated below. The working substance of the cycle is assumed to be air. The six steps of the Otto cycle ale as follows: i. Isobaric intake stroke (OA). A mixture of gasoline and air is drawn into the combustion chamber at atmospheric pressure P0 as the piston expands, increasing the volume of the cylinder from zero to VA . ii. Adiabatic compression stroke (AB). The temperature of the mixture rises as the piston compresses it adiabatically from a volume VA to VB . iii. Ignition at constant volume (BC). The mixture is ignited by a spark. The combustion happens so fast that there is essentially no motion of the piston. During this process, the added heat Q1 causes the pressure to increase from pB to pc at the constant volume VB(=Vc) . iv. Adiabatic expansion (CD). The heated mixture of gasoline and air expands against the piston, increasing the volume from VC to VD . This is called the power stroke, as it is the part of the cycle that delivers most of the power to the crankshaft. v. Constant-volume exhaust (DA). When the exhaust valve opens, some of the combustion products escape. There is almost no movement of the piston during this part of the cycle, so the volume remains constant at VA(=VD) . Most of the available energy is lost here, as represented by the heat exhaust Q2 . vi. Isobaric compression (AO). The exhaust valve remains open, and the compression from VA to zero drives out the remaining combustion products. (a). Using (i)e=W/Q1; (ii)w=Q1Q2; and (iii)Q1=nCv(TCTB),Q2=nCv(TDTA), Show that e=1TDTATCTB. (b). Use the fact that steps (ii) and (iv) are adiabatic to show that e=11r1 where r=VA/VB . The quantity r is called the compression ratio of the engine. (c) In practice, r is kept less than around 7. For larger values, the gasoline-air mixture is compressed to temperatures so high that it explodes before the finely timed spark is delivered. This preignition causes engine knock and loss of power. Show that for r=6 and =1.4 (the value for air), e=0.51 , or an efficiency of 51%. Because of the many irreversible processes, an actual internal combustion engine has an efficiency much less than this ideal value. A typical efficiency for a tuned engine is about 25% to 30%.
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