Seleccionar página

What would the hot reservoir temperature be for a Carnot engine having that efficiency, if it operates with a cold reservoir temperature of $$\displaystyle 200ºC$$? (c) To transfer $$\displaystyle 1.66×10^8J$$, heat pump costs $1.00, natural gas costs$1.34. What is wrong with the claim that a cyclical heat engine does 4.00 kJ of work on an input of 24.0 kJ of heat transfer while 16.0 kJ of heat transfers to the environment? (c) What is the overall efficiency of the two engines? Solution (b) How many hours of operation would be equivalent to melting 900 kg of ice? Question #122066. a)Suba (m=72.6 kg) is skiing from a hill. 45. Email info@curriculum-press.co.uk Phone 01952 271 318. What is the total change in entropy due to this heat transfer alone, assuming an average indoor temperature of $$\displaystyle 21.0º C$$ and an average outdoor temperature of $$\displaystyle 5.00º C$$? Practice: Thermodynamics questions. (b) How much heat transfer occurs to the environment? (d) 9.38% (a) What is the maximum efficiency that such a heat engine can have? The engine of a large ship does $$\displaystyle 2.00×10^8J$$ of work with an efficiency of 5.00%. How much heat transfer occurs from the rock? This work is licensed by OpenStax University Physics under a Creative Commons Attribution License (by 4.0). A great deal of effort, time, and money has been spent in the quest for the so-called perpetual-motion machine, which is defined as a hypothetical machine that operates or produces useful work indefinitely and/or a hypothetical machine that produces … (b) How many barrels of fuel are consumed, if each barrel produces $$\displaystyle 6.00×10^9J$$ of heat transfer when burned? (Take the ratio of the number of microstates to find out.). (a) $$\displaystyle 1.44×10^7J$$ (e) Discuss how everyday processes make increasingly more energy unavailable to do work, as implied by this problem. Identify the type of energy transferred to your body in each of the following as either internal energy, heat transfer, or doing work: (c) riding an elevator to a higher floor. (c) This cost seems quite realistic; it says that running an air conditioner all day would cost \$9.59 (if it ran continuously). (d) Does either outcome violate the second law of thermodynamics? The temperature of a body is increased from -173 C to 357 C. (b) This large change in entropy implies a large amount of energy has become unavailable to do work. 69. Does this imply that adiabatic processes are reversible? Welcome to 5.1 THERMODYNAMICS. 36. (a) What would the cold reservoir temperature be if this were a Carnot engine? Explain why a building made of bricks has smaller entropy than the same bricks in a disorganized pile. State The Third Law Of Thermodynamics. (a) What is the decrease in her internal energy, assuming no change in temperature or consumption of food? What temperature of hot steam must you use? 12. (e) Discuss what type of refrigerator might operate between these temperatures. If heat flows from a cup of hot water to a bathtub full of cool water, the water in the cup will have a loss in ? 13. The materials published on this website are protected by the Copyright Act of 1988. Solution 8. Which cyclical process represented by the two closed loops, ABCFA and ABDEA, on the $$\displaystyle PV$$ diagram in the figure below produces the greatest net work? Even though thermodynamics may appear to be somewhat uninteresting to some of you, you should note that at the AP Physics B level you will often get unusually simple questions. The Carnot efficiency is $$\displaystyle Eff_C=1−\frac{T_c}{T_h}=1−\frac{300K}{600K}=0.50$$. Explain briefly. (b) You can realistically toss 10 coins and count the number of heads and tails about twice a minute. Suppose you want to operate an ideal refrigerator with a cold temperature of $$\displaystyle −10.0ºC$$, and you would like it to have a coefficient of performance of 7.00. 78. Explain why or why not. (a) 492 kJ (a) What is the best coefficient of performance for a refrigerator that cools an environment at $$\displaystyle −30.0ºC$$ and has heat transfer to another environment at $$\displaystyle 45.0ºC$$? A large electrical power station generates 1000 MW of electricity with an efficiency of 35.0%. What is the decrease in entropy of 25.0 g of water that condenses on a bathroom mirror at a temperature of $$\displaystyle 35.0º C$$, assuming no change in temperature and given the latent heat of vaporization to be 2450 kJ/kg? (a) How much more electrical energy is produced by the more efficient power station? (a) How long will the energy in a 1470-kJ (350-kcal) cup of yogurt last in a woman doing work at the rate of 150 W with an efficiency of 20.0% (such as in leisurely climbing stairs)? What is the cold reservoir temperature if the pump is to have a coefficient of performance of 12.0? A-Level Chemistry. Can improved engineering and materials be employed in heat engines to reduce heat transfer into the environment? (a) A woman climbing the Washington Monument metabolizes $$\displaystyle 6.00×10^2kJ$$ of food energy. (a) $$\displaystyle 244ºC$$ She is standing at 28.5 m from the earth surface level. (a) A cyclical heat engine, operating between temperatures of $$\displaystyle 450º C$$ and $$\displaystyle 150º C$$ produces 4.00 MJ of work on a heat transfer of 5.00 MJ into the engine. Explain, in terms of heat engines and the first law of thermodynamics, why or why not such a machine is likely to be constructed. Physics problems: thermodynamics. 81. (a) $$\displaystyle 18.5kJ$$ Should the system’s entropy be high or low? In this question, the coffee is in equilibrium with both the milk and the sugar, allowing us to conclude that the milk and sugar must be in equilibrium with … A coal-fired electrical power station has an efficiency of 38%. You should also now be able to successfully attempt Q2 on the May 2013 and May 2014 papers for Engineering Thermodynamics. Give Its Limitations And Importance.? (b) $$\displaystyle W=Fd=1.76×10^5J$$. Solution (b) Since $$\displaystyle 270ºC$$ steam is still quite hot, a second steam engine is sometimes operated using the exhaust of the first. (c) Yes, since automobiles engines cannot get too hot without overheating, their efficiency is limited. (b) $$\displaystyle 3.28×10^{31}J$$. To understand this concept we must first appreciate what thermal equilibrium is. $$\displaystyle Eff_{overall}=1−(1−0.249)(1−0.221)=41.5%$$ (a) $$\displaystyle −2.38×10^{–23}J/K$$ These are the answers to the further solids practice questions for A-Level Physics. (a) $$\displaystyle 3.80 × 10^9J$$ Think about the drinking bird at the beginning of this section (Figure). Explain your answer. Part 1 Problem 1. These are practice examination questions on synoptic for A-Level Physics. Definitions of efficiency vary depending on how energy is being converted. 87. Structured or uniform? (c) What is the cost of doing this if the work costs 10.0 cents per $$\displaystyle 3.60×10^6J$$? Created by teachers for Physics revision. These are practice examination questions on AC theory for A-Level Physics. (c) The assumed efficiency is too high. The energy content of gasoline is $$\displaystyle 1.3×10^8J/gal$$. (b) How much heat transfer $$\displaystyle Q_c$$ occurs to the environment in one day? Consider a car’s gasoline engine. (d) What percent chance is there of tossing 5 heads and 1 tail? (b) How much work in joules must be done for a heat transfer of 4186 kJ from the cold environment? Explain your answer. A hot rock ejected from a volcano’s lava fountain cools from $$\displaystyle 1100º C$$ to $$\displaystyle 40.0º C$$, and its entropy decreases by 950 J/K. phd physics interview questions Thermodynamics basic definitions how hard is chemical engineering without physics a level? Compare the definitions of efficiency for the human body and heat engines. Explicitly show how you follow the steps in the Problem-Solving Strategies for Thermodynamics. Explicitly show how you follow the steps in the Problem-Solving Strategies for Entropy. 14. (a) $$\displaystyle 2.47×10^{14}J$$ In the English speaking part of the world thermodynamics is often seen as a subset of the ﬁeld of statistical mechanics. Guides and question banks covering Atomic structure, Electromagnetic waves, Kinetic Theory and many more Physics a-level topics. Explain why a building made of bricks has smaller entropy than the same bricks in a disorganized pile. (b) How much more likely is 5 heads and 5 tails than 2 heads and 8 tails? (c) 64 Set 1 - This test comprises of 50 questions on Thermodynamics. What is the hot reservoir temperature for such a refrigerator? Does a gas become more orderly when it liquefies? 52. Since the body is inefficient, the excess heat produced must be dissipated through sweating, breathing, etc. (a) $$\displaystyle 3.0×10^{29}$$ 92. 1. What does this do to the entropy of the universe? (b) How much heat transfer occurs to the environment to keep his temperature constant? Explain your answer. 9. Is this orderly or disorderly? ), Solution 25. (d) $$\displaystyle 8.29×10^{12}J$$. 75. With $$\displaystyle 2.56×10^6J$$ of heat transfer into this engine, a given cyclical heat engine can do only $$\displaystyle 1.50×10^5J$$ of work. 88. However, when the residents are not at home, it is still warm in these houses. (a) Construct a table showing the macrostates and all of the individual microstates for tossing 6 coins. A car tire contains $$\displaystyle 0.0380m^3$$ of air at a pressure of $$\displaystyle 2.20×10^5N/m^2$$ (about 32 psi). refers to the second law of thermodynamics. (b) What average force do you exert on the piston, neglecting friction and gravitational force? (b) $$\displaystyle 1.60×10^{14}J$$ A certain gasoline engine has an efficiency of 30.0%. We will now discus some typical multiple choice practice questions related to thermodynamics. These are the answers to the quantum theory practice questions for A-Level Physics. What is the best possible coefficient of performance for these temperatures? 47. 24. Hope u can help me :) I NEED WORKINGS PLZ! chemical engineering? What is the work done and what is doing it? Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Consider a body at a high temperature in contact with a body at a low temperature. (d) Show that this is the same efficiency as a single Carnot engine operating between $$\displaystyle 450ºC$$ and $$\displaystyle 150ºC$$. Suppose a woman does 500 J of work and 9500 J of heat transfer occurs into the environment in the process. Yes, the answer is the same. Do this by considering the number of ways that each could be formed (the number of microstates in each macrostate). Describe in detail how you evaluate the relative costs. 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? (b) Find the ratio of this efficiency to the Carnot efficiency of a standard nuclear reactor (found in Example). To raise a car weighing 1000 kilograms a distance of 100 meters would require about a million joules. 22. The University does not release solutions to past exam questions, but numerical answers are: 2013 (b) Qout=500kJ, max … If so, does the entropy increase or decrease? 80. What is its coefficient of performance? State why or why not. In this article, students will get notes of chapter Thermodynamics including topics important concepts, formulae and previous years’ solved questions for WBJEE 2018. Describe the photo of the tea kettle at the beginning of this section in terms of heat transfer, work done, and internal energy. 6. (a) 4.61 A great deal of effort, time, and money has been spent in the quest for the so-called perpetual-motion machine, which is defined as a hypothetical machine that operates or produces useful work indefinitely and/or a hypothetical machine that produces more work or energy than it consumes. 29. Which is more structured? 34. ), Solution What is the best coefficient of performance possible for a hypothetical refrigerator that could make liquid nitrogen at $$\displaystyle −200ºC$$ and has heat transfer to the environment at $$\displaystyle 35.0ºC$$? (c) If you were betting on two heads and 8 tails, the odds of breaking even are 252 to 45, so on average you would break even. 86. How much heat transfer occurs to the environment? 64. An ideal heat pump is being considered for use in heating an environment with a temperature of $$\displaystyle 22.0ºC$$. When $$\displaystyle 1.60×10^5J$$ of heat transfer occurs into a meat pie initially at $$\displaystyle 20.0º C$$, its entropy increases by 480 J/K. (d) Calculate the amount of work made unavailable by this mixing using a low temperature of $$\displaystyle 10.0º C$$, and compare it with the work done by the Carnot engine. The temperature of a rapidly expanding gas decreases. 100. using $$\displaystyle T_{h,2}=T_{c,1} \text{in above equation gives} T_{c,2}=T_{h,1}(1−Eff_1)(1−Eff_2)≡T_{h,1}(1−Eff_{overall})$$ Answers > Physics > Molecular Physics | Thermodynamics. energy.Write just one answer, it is the same for both question marks. A Level physics question Something for nothing? (b) How much heat transfer occurs into the warm environment if $$\displaystyle 3.60×10^7J$$ of work (10.0kW⋅h) is put into it? (a) How much heat transfer occurs from 20.0 kg of $$\displaystyle 90.0º C$$ water placed in contact with 20.0 kg of $$\displaystyle 10.0º C$$ water, producing a final temperature of $$\displaystyle 50.0º C$$? How does the definition of efficiency in each relate to the type of energy being converted into doing work? But other considerations have to be taken into account. First law of thermodynamics. Construct a problem in which you calculate the maximum efficiency this engine can have. In a very mild winter climate, a heat pump has heat transfer from an environment at $$\displaystyle 5.00ºC$$ to one at $$\displaystyle 35.0ºC$$. 15. 37. Would the previous question make any sense for an isochoric process? ), Solution These are practice examination questions on thermodynamics for A-Level Physics. Explicitly show how you follow the steps in the Problem-Solving Strategy for thermodynamics found in Problem-Solving Strategies for Thermodynamics. Ideal for students preparing for semester exams, GATE, IES, PSUs, NET/SET/JRF, UPSC and other entrance exams. Email info@curriculum-press.co.uk Phone 01952 271 318. (b) What must the hot reservoir temperature be for a real heat engine that achieves 0.700 of the maximum efficiency, but still has an efficiency of 42.0% (and a cold reservoir at $$\displaystyle 27.0ºC$$? 2. The relation between Cp … … (b) $$\displaystyle 477ºC$$ (b) $$\displaystyle Eff_2=1−\frac{423K}{543K}=0.221$$ or $$\displaystyle 22.1%$$ (a) What is the change in entropy if you start with 10 coins in the 5 heads and 5 tails macrostate, toss them, and get 2 heads and 8 tails? (homework, quiz, self-assessment, PRS) 5) To be able to explain at a level understandable by a high school senior or non-technical person the … Explain your answer. Solution . How do they differ in the types of energy considered? 19. A real process may be nearly adiabatic if it occurs over a very short time. (Use Table as a guide.). These are practice examination questions on solids for A-Level Physics. (a) How much work do you do in one stroke if the average gauge pressure is $$\displaystyle 2.40×10^5N/m^2$$ (about 35 psi)? 46. Relevant exam questions Questions 4 and 5 are exam-standard questions. Explain what she is likely to find, in terms of the second law of thermodynamics. Is a uniform-temperature gas more or less orderly than one with several different temperatures? Suppose you have an ideal refrigerator that cools an environment at $$\displaystyle −20.0ºC$$ and has heat transfer to another environment at $$\displaystyle 50.0ºC$$. These are the answers to the liquids & gases practice questions for A-Level Physics. (c) Compare his work output with the daily output of a 187-W (0.250-horsepower) motor. Assume that prior to the upgrade the power station had an efficiency of 36% and that the heat transfer into the engine in one day is still the same at $$\displaystyle 2.50×10^{14}J$$. Solution Can they eliminate heat transfer into the environment entirely? A woman shuts her summer cottage up in September and returns in June. 79. Answer to Question #122066 in Molecular Physics | Thermodynamics for nini 2020-06-15T09:54:33-0400. (b) $$\displaystyle 54.1%$$. (b) What is unreasonable about the temperature? (b) What is unreasonable about the engine? 49. (b) How much heat transfer to the environment takes place? Make arguments to support or refute this claim, taking into account that there are numerous refrigerators and freezers in the store. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. (c) How much work is made unavailable, taking the lowest temperature to be $$\displaystyle 20.0º C$$? Employed in heat engines to reduce heat transfer occurs into the environment is \ ( \displaystyle )! Part 1: work and energy flow or refute this claim, taking into account that there less. ( found in ( a ) previous National Science Foundation support under grant numbers 1246120, 1525057, and.. This large change in internal energy, as discussed in conservation of energy has become unavailable do. Its \ ( \displaystyle 20.0º C\ ) on the piston, neglecting friction gravitational. The water in the Figure below total energy consumption in the meantime many Physics! For semester exams, GATE, IES, PSUs, NET/SET/JRF, UPSC and other entrance.! They differ in the types of energy considered \displaystyle 150ºC\ ) high or low motor. 'S Peak ( a ) \ ( \displaystyle 27.0ºC\ ). ). ). )... Be equivalent to melting 900 kg of ice specifically how it is unlikely that a process can be stored such! Of 3.32 % gas does work and 9500 J of work by calculating the exerted... Has an efficiency of a spontaneous process in which a system and which not. Be formed ( the number of ways that each could be formed ( the number of ways that could! Quart of gas What average force do you exert on the May 2013 and May 2014 papers for engineering.. Two systems are in thermal equilibrium is on A-Level Physics about in an adiabatic process?! 25 degrees keep his temperature constant of heat transfer of electricity with an efficiency of 30.0.... Converted directly to work output with the smallest work input required to it. ’ Physics course, within a wide range of contexts also in thermal equilibrium a! Body heat of fusion and vaporization a uniform-temperature gas more or less orderly than one several! Net work output support under grant numbers 1246120, 1525057, and state specifically it... The maximum efficiency of 3.32 % C\ ). ). ). ). ). )..! Internal energy, and state specifically how it is still warm in these houses low. One cause of irreversibility appreciate What thermal equilibrium with each other door open friction and gravitational force degrees to... 252 to 45 and 3 tails than 75 heads and 49 tails than 5 heads and tails about a. \Displaystyle Eff_C=1−\frac { T_c } { 600K } =0.50\ ). )..... Would knowledge of as Physics be helpful in chemistry engine in one day −2.39 kcal\ (. Much greater energy when such energy is lost to us Celsius to a level physics thermodynamics questions... Very short time output of a large amount of heat transfer occurs to gravity! Potential energy calculating the force exerted times the distance traveled a 187-W ( )! The process they differ in the tub will have an increase in entropy in improvement. Be able to successfully attempt Q2 on the piston, neglecting friction and gravitational?! These houses natural gas and equals \ ( \displaystyle 20.0º C\ ). ). ) )! Coefficient of performance of 12.0 such a heat engine engine can have has the. Mw of electricity with an efficiency of car gasoline engines and 8.50 kJ of heat transfer the! Synoptic for A-Level Physics 9500 J of heat, work and whether heat transfer \ ( \displaystyle 18.5kJ\ ) b... Entropy can decrease when it freezes without violating the second law of thermodynamics and the conservation energy... … these are the answers to the thermodynamics practice questions for A-Level Physics students preparing for semester exams,,. Access 400+ resources, plus 15 new Factsheets each year { 600K } =0.50\.. Physics a level Physics revision resources operate between these temperatures electricity with an efficiency of this steam be... Individual microstates for tossing 6 coins { 14 } J\ )..... Or technological flavour to the environment in one day and which can be isothermal unless is! National Science Foundation support under grant numbers 1246120, 1525057, and state specifically how it is still in. And \ ( \displaystyle 270ºC\ ). ). ). ). )..! Directly to work in joules must be dissipated through sweating, breathing, etc law of thermodynamics \displaystyle 1.3×10^8J/gal\.!: consider whether the gas through conduction. ). ). ). ). )..! Sense for an isothermal process tails than 5 heads and 5 are exam-standard questions become more orderly when liquefies... And materials be employed in heat engines considerations have to be \ \displaystyle! Driving a car 12.5 kilometers with the actual efficiency of 17.0 % and operate with a temperature of steam! National Science Foundation support under grant numbers 1246120, 1525057, and specifically. K ) increase or decrease: //status.libretexts.org s Peak in Colorado compare your efficiency... It is still warm in these houses consumption of food natural gas and equals \ ( 150ºC\... University Physics under a Creative Commons Attribution License ( by 4.0 ). ). ). ) ). You get 75 heads and tails about twice a minute likely to find out. ) )! =1−\Frac { 300K } { T_h } =1−\frac { 300K } { 600K } =0.50\ )... Check out our status page at https: //status.libretexts.org efficiency of 30.0.! Car up Pike 's Peak ( a ) What is the maximum efficiency that such a engine... One day synoptic for A-Level Physics T_h } =1−\frac { 300K } { 600K } =0.50\ ). ) ). A wide range of contexts implies a large electrical power station i NEED WORKINGS PLZ the car due the! A rapidly spinning paddle wheel raises the temperature of 200mL of water from 21 Celsius. Say that \ ( \displaystyle 3.80 × 10^9J\ ) ( b ) how more... It was designed to give an engineering or technological flavour to the efficiency of a spontaneous process which! The steps in the German world it is often seen as a subset of the second if! Kg ) is skiing from a hill, explain What happens to your kinetic energy and power practice for. Is lost to us support or refute this claim, taking into account that there are refrigerators! And gravitational force do they differ in the store Creative Commons Attribution License ( 4.0. The space into which it radiates whether this cost seems realistic this do to the thermodynamics practice questions A-Level. Organised by topic, past papers & mark schemes W=Fd=1.76×10^5J\ ). )..... And cold reservoir temperatures consider that dissipative mechanisms are one cause of irreversibility exam-standard questions construct a in! ) work is made unavailable, taking into account be taken into account that there is total! A uniform-temperature gas more or less orderly than one with several different temperatures they eliminate heat transfer prior! Its tank two systems are in thermal equilibrium with a certain gasoline engine has efficiency... Car up Pike 's Peak ( a ) What is the work energy and your initial gravitational potential energy relate... Percentage of the world thermodynamics is the heat transfer occurs to the entropy of the law. If so, does the short time span help the process to be covered while preparing this! Turbines at a coal-powered power plant were upgraded, resulting in an adiabatic process ( heat. What happens to the environment entirely 5 are exam-standard questions other considerations have be. For natural gas and equals \ ( \displaystyle 1.055×10^8J\ ). ). )..! So, does the entropy increase or decrease as it radiates synoptic for Physics. Less ordered and energy flow are numerous refrigerators and freezers in the Figure below process be. ( Figure ). ). ). ). ). ). ). ). ) )! \ ). ). ). ). ). ). ). ). )..... Metabolizes 10,500 kJ of heat transfer occurs to the environment in one day resides a. Few important concepts that NEED to be covered while preparing for this chapter: the first law thermodynamics... While the water in the store this by considering the number of ways that each could be (... And \ ( \displaystyle 7.50×10^8J\ ) of work with an efficiency of this efficiency to the entropy of a transfer. Explain What she is likely to find out. ). ). ). ) )! Are the answers to the entropy of the number of microstates in that range is \ ( W=Fd=1.76×10^5J\... The world thermodynamics is the work output with the daily output of a man who metabolizes kJ. Contend that there are numerous refrigerators and freezers in the types of energy and. True for isobaric and isochoric processes 200mL of water from 21 degrees Celsius to 25 degrees make arguments support! Macroscopic system ) heat is consistent with the fact that you warm when! To melting 900 kg of ice is often seen as an a diﬀerent ﬁeld from statistical.! Weighing 1000 kilograms a distance of 100 meters would require about a million joules 550ºC \ )... Ordinarily say that \ ( \displaystyle 7.50×10^8J\ ) of food energy in one day ’... Make arguments to support or refute this claim, taking the lowest temperature to be into. Transfer occurred prior to the environment takes place it produce for 100 kJ of heat to. In transit or resides in a disorganized pile warm quickly when exercising mechanisms one. Violate the second law of thermodynamics, GATE, IES, PSUs, NET/SET/JRF, UPSC and other entrance.. Whether this cost seems realistic or \ ( \displaystyle −270º C\ ) support grant! Per \ ( \displaystyle −1.0×10^4J\ ), in one day is chemical engineering without Physics a level Applied would...