(b) What is unreasonable about the temperature? Email info@curriculum-press.co.uk Phone 01952 271 318. 101. Give an example of a spontaneous process in which a system becomes less ordered and energy becomes less available to do work. These are practice examination questions on synoptic for A-Level Physics. 18. How do they differ in the types of energy considered? What is the net work output of a heat engine that follows path ABDA in the figure above, with a straight line from B to D? Give an explanation of how food energy (calories) can be viewed as molecular potential energy (consistent with the atomic and molecular definition of internal energy). These are the answers to the liquids & gases practice questions for A-Level Physics. The second law of thermodynamics. (b) \(\displaystyle 54.1%\). Solution 54. 11. Solution (a) What is the work output of a cyclical heat engine having a 22.0% efficiency and \(\displaystyle 6.00×10^9J\) of heat transfer into the engine? 26. (b) Now find the amount of work by calculating the force exerted times the distance traveled. It was designed to give an engineering or technological flavour to the students’ physics course, within a wide range of contexts. What is the maximum efficiency of the second engine if its exhaust has a temperature of \(\displaystyle 150ºC\)? (a) –56.3ºC What is the change in entropy in an adiabatic process? First law of thermodynamics. Imagine you are driving a car up Pike’s Peak in Colorado. Created by teachers for Physics revision. (d) Does either outcome violate the second law of thermodynamics? Have questions or comments? In which can heat transfer result in work done without heat transfer from another system? (d) How many kJ of heat transfer occurs into the warm environment? A certain heat engine does 10.0 kJ of work and 8.50 kJ of heat transfer occurs to the environment in a cyclical process. (Consult Table.). 41. These are practice examination questions on thermodynamics for A-Level Physics. (a) If tossing 100 coins, how many ways (microstates) are there to get the three most likely macrostates of 49 heads and 51 tails, 50 heads and 50 tails, and 51 heads and 49 tails? Solution These are practice examination questions on thermodynamics for A-Level Physics. (c) To transfer \(\displaystyle 1.66×10^8J\), heat pump costs $1.00, natural gas costs $1.34. (a) How much heat transfer occurs to the environment? 49. (c) Compare his work output with the daily output of a 187-W (0.250-horsepower) motor. Resources About Services Blog Contact Resources About Services Blog What is its coefficient of performance? (b) \(\displaystyle –8.30 × 10^{12}J\), where the negative sign indicates a reduction in heat transfer to the environment. A helium-filled toy balloon has a gauge pressure of 0.200 atm and a volume of 10.0 L. How much greater is the internal energy of the helium in the balloon than it would be at zero gauge pressure? Start with the definitions of the \(\displaystyle COP\) s and the conservation of energy relationship between \(\displaystyle Q_h, Q_c,\) and \(\displaystyle W\). 96. Explain your answer. 25. If you run down some stairs and stop, what happens to your kinetic energy and your initial gravitational potential energy? 36. Specifically, explain what happens to the entropy of its surroundings. (d) Show that this is the same efficiency as a single Carnot engine operating between \(\displaystyle 450ºC\) and \(\displaystyle 150ºC\). Would the previous question make any sense for an isochoric process? (c) What is the total number of microstates? Solution (a) What is the maximum efficiency of a heat engine operating between these temperatures? How do heat transfer and internal energy differ? 71. First law of thermodynamics problem solving. State why or why not. 82. The total number of microstates in that range is \(\displaystyle 1.22×10^{30}\). (Assume the temperature of the environment is \(\displaystyle 20ºC\).). The Sun radiates energy at the rate of \(\displaystyle 3.80×10^{26}W\) from its \(\displaystyle 5500º C\) surface into dark empty space (a negligible fraction radiates onto Earth and the other planets). (b) How many hours of operation would be equivalent to melting 900 kg of ice? 97. The energy content of gasoline is \(\displaystyle 1.3×10^8J/gal\). (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? Since the body is inefficient, the excess heat produced must be dissipated through sweating, breathing, etc. What is the increase in entropy of the car due to this heat transfer alone? Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. (a) What is the change in entropy if you start with 100 coins in the 45 heads and 55 tails macrostate, toss them, and get 51 heads and 49 tails? Can improved engineering and materials be employed in heat engines to reduce heat transfer into the environment? Consider a system with a certain energy content, from which we wish to extract as much work as possible. (a) What is the efficiency of a cyclical heat engine in which 75.0 kJ of heat transfer occurs to the environment for every 95.0 kJ of heat transfer into the engine? (c) The assumed efficiency is too high. (a) \(\displaystyle 9.78×10^4J/K\) (Take the ratio of the number of microstates to find out.). NEET Physics - Mini Question Bank Thermodynamics questions & solutions with PDF and difficulty level energy.Write just one answer, it is the same for both question marks. Welcome to 5.1 THERMODYNAMICS. 76. (b) How much more likely is 5 heads and 5 tails than 2 heads and 8 tails? In this article, students will get notes of chapter Thermodynamics including topics important concepts, formulae and previous years’ solved questions for WBJEE 2018. State The Third Law Of Thermodynamics. Suppose a woman does 500 J of work and 9500 J of heat transfer occurs into the environment in the process. Explain your answer. 81. (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 \(\displaystyle 45.0ºC\)? The heat transfer to the cold reservoir is \(\displaystyle Q_c=Q_h−W=25kJ−12kJ=13kJ\), so the efficiency is \(\displaystyle Eff=1−\frac{Q_c}{Q_h}=1−\frac{13kJ}{25kJ}=0.48\). 40. Set 1 - This test comprises of 50 questions on Thermodynamics. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. (a) 122 W (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. Should the system’s entropy be high or low? 69. (a) Construct a table showing the macrostates and all of the individual microstates for tossing 6 coins. Solution These are the answers to the further kinetic theory of gases practice questions for A-Level Physics. 19. Explain, in terms of efficiency, what factors may keep you from realizing your ideal energy use on this trip. Ideal for students preparing for semester exams, GATE, IES, PSUs, NET/SET/JRF, UPSC and other entrance exams. 44. A system does \(\displaystyle 1.80×10^8J\) of work while \(\displaystyle 7.50×10^8J\) of heat transfer occurs to the environment. Driving up Pike's Peak (a mere 3000-meter climb) should consume a little less than a quart of gas. 63. 68. A-Level Chemistry. 33. What is the cold reservoir temperature if the pump is to have a coefficient of performance of 12.0? (a) What is the maximum efficiency that such a heat engine can have? Is the same true for isobaric and isochoric processes? The engine of a large ship does \(\displaystyle 2.00×10^8J\) of work with an efficiency of 5.00%. 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? But other considerations have to be taken into account. PV diagrams - part 1: Work and isobaric … (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 \(\displaystyle 50.0º C\)? (b) In order to gain more energy, we must generate it from things within the house, like a heat pump, human bodies, and other appliances. 39. Answers > Physics > Molecular Physics | Thermodynamics. 50. What is the coefficient of performance of an ideal heat pump that has heat transfer from a cold temperature of \(\displaystyle −25.0ºC\) to a hot temperature of \(\displaystyle 40.0ºC\)? (Use Table as a guide.). (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)? (d) 9.38% (b) How much work does it produce for 100 kJ of heat transfer into the engine? (b) Find the ratio of this efficiency to the Carnot efficiency of a standard nuclear reactor (found in Example). (b) How much heat transfer occurs to the environment to keep his temperature constant? (a) \(\displaystyle 2.47×10^{14}J\) using \(\displaystyle T_{h,2}=T_{c,1} \text{in above equation gives} T_{c,2}=T_{h,1}(1−Eff_1)(1−Eff_2)≡T_{h,1}(1−Eff_{overall})\) (a) How much more electrical energy is produced due to the upgrade? So, no, you wouldn’t bet on odds of 252 to 45. (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? (A therm is a common unit of energy for natural gas and equals \(\displaystyle 1.055×10^8J\).). 6. Note that the energy efficiency rating (\(\displaystyle EER\)) of an air conditioner or refrigerator is defined to be the number of British thermal units of heat transfer from a cold environment per hour divided by the watts of power input. 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. (d) \(\displaystyle Eff_{overall}=1−\frac{423K}{723K}=0.415\) or \(\displaystyle 41.5%\), 70. The Engineering Physics optional unit gives students the opportunity to use their knowledge and understanding of dynamics and thermal physics gained in sections 3.4.1 and 3.6.2. ΔU=Q in −W Work done by the system Example: expanding gas pushes a piston Work done on the system Example: … A hand-driven tire pump has a piston with a 2.50-cm diameter and a maximum stroke of 30.0 cm. Explain why. 37. Construct a problem in which you calculate the overall efficiency of the car for the trip as a ratio of kinetic and potential energy gained to fuel consumed. Steam locomotives have an efficiency of 17.0% and operate with a hot steam temperature of \(\displaystyle 425ºC\). (a) \(\displaystyle 3.0×10^{29}\) I have some questions on Thermodynamics on A-level physics. Describe in detail how you evaluate the relative costs. Suppose both have the same heat transfer into the engine in one day, \(\displaystyle 2.50×10^{14}J\). 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 \(\displaystyle 2.50×10^{14}J\). Consider that dissipative mechanisms are one cause of irreversibility. (b) How much less heat transfer occurs to the environment due to the upgrade? Practice: Thermodynamics questions. 4/17/14 Physics 115 11 • st1 Law of Thermodynamics: The change in internal energy of a system equals the heat transfer into the system plus the work done by the system. (a) \(\displaystyle −1.0×10^4J\), or \(\displaystyle −2.39 kcal\) Solution 2. However, when the residents are not at home, it is still warm in these houses. (b) What average force do you exert on the piston, neglecting friction and gravitational force? (Note that the temperatures of the cycle employed are crucial to its \(\displaystyle COP\).). (b) \(\displaystyle 2.10×10^6J\) Make arguments to support or refute this claim, taking into account that there are numerous refrigerators and freezers in the store. 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? Solution Why—other than the fact that the second law of thermodynamics says reversible engines are the most efficient—should heat engines employing reversible processes be more efficient than those employing irreversible processes? (c) Yes, since automobiles engines cannot get too hot without overheating, their efficiency is limited. Can you cool a kitchen by leaving the refrigerator door open? (Hint: Consider whether the gas does work and whether heat transfer occurs rapidly into the gas through conduction.). 89. 9. (c) What is the overall efficiency of the two engines? 24. Explicitly show how you follow the steps in the Problem-Solving Strategies for Thermodynamics. \(\displaystyle ∴(1−Eff_{overall})=(1−Eff_1)(1−Eff_2)\) In an air conditioner, 12.65 MJ of heat transfer occurs from a cold environment in 1.00 h. (a) What mass of ice melting would involve the same heat transfer? 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 ? (a) 4.61 (c) \(\displaystyle Eff_1=1−\frac{T_{c,1}}{T_{h,1}}⇒T_{c,1}=T_{h,1}(1,−,eff_1)\) similarly, \(\displaystyle T_{c,2}=T_{h,2}(1−Eff_2)\) In the German world it is often seen as an a different field from statistical mechanics. 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. (b) 40 cents Does a gas become more orderly when it liquefies? Solution No one has entered the cottage in the meantime. 94. Part 1 Problem 1. Specific heat and latent heat of fusion and vaporization. ... at sea level (b) at the center of the earth (c) when molecular momentum of the system becomes zero (d) under vacuum conditions 67. (a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of \(\displaystyle 50.0ºC\) and a cold reservoir temperature of \(\displaystyle −20.0ºC\)? (b) What percent of the total possibilities is this? (b) \(\displaystyle 1.60×10^{14}J\) (b) How much work could a Carnot engine do with this heat transfer, assuming it operates between two reservoirs at constant temperatures of \(\displaystyle 90.0º C\) and \(\displaystyle 10.0º C\)? In particular, which can be stored as such in a system and which cannot? Compare your calculated efficiency with the actual efficiency of car engines. Solution 29. (Essentially: conservation of energy). A gas-cooled nuclear reactor operates between hot and cold reservoir temperatures of \(\displaystyle 700ºC\) and \(\displaystyle 27.0ºC\). Upgraded, resulting in an isobaric process, or \ ( \displaystyle 1.22×10^ 30. 21 degrees Celsius to 25 degrees 550ºC \ ). ). ). ) )... 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For A-Level Physics some stairs and stop, What factors May keep you from realizing your ideal energy on! Temperature if the pump is to have a coefficient of performance for these temperatures the law! Transferred in this process in a cyclical process its cold reservoir temperature for a... Ship does \ ( \displaystyle 1.055×10^8J\ ). ). ). ). )... Problem-Solving Strategies for entropy is \ ( \displaystyle 1.32 × 10^9J\ ) ( b 0.667! Cyclical process woman shuts her summer cottage up in September and returns in June work! Best possible coefficient of performance for these temperatures are being built without heating systems of type. Appreciate What thermal equilibrium with each other few important concepts that NEED to be into!