(d) Does either outcome violate the second law of thermodynamics? phd physics interview questions Thermodynamics basic definitions how hard is chemical engineering without physics a level? Explain why. How much heat transfer occurs from the rock? (b) How much less heat transfer occurs to the environment by the more efficient power station? 88. (d) Show that this is the same efficiency as a single Carnot engine operating between \(\displaystyle 450ºC\) and \(\displaystyle 150ºC\). 69. However, when the residents are not at home, it is still warm in these houses. (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? What happens to the system’s entropy in this process? 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? A rapidly spinning paddle wheel raises the temperature of 200mL of water from 21 degrees Celsius to 25 degrees. Thermodynamics to a system of thermodynamic components (heaters, coolers, pumps, turbines, pistons, etc.) (c) If you were betting on 2 heads and 8 tails would you accept odds of 252 to 45? (a) \(\displaystyle 18.5kJ\) ), Solution Does a gas become more orderly when it liquefies? (a) \(\displaystyle 2.47×10^{14}J\) 84. If you run down some stairs and stop, what happens to your kinetic energy and your initial gravitational potential energy? (b) How much heat transfer to the environment takes place? (a) What would the cold reservoir temperature be if this were a Carnot engine? Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. 28. Start with the definitions of the \(\displaystyle COP\) s and the conservation of energy relationship between \(\displaystyle Q_h, Q_c,\) and \(\displaystyle W\). (b) You can realistically toss 10 coins and count the number of heads and tails about twice a minute. 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. Created by teachers for Physics revision. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. 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 practice examination questions on solids for A-Level Physics. (b) This large change in entropy implies a large amount of energy has become unavailable to do work. \(\displaystyle W\) is not equal to the difference between the heat input and the heat output. Answers For Thermodynamics Problems Answer for Problem # 1 Since the containers are insulated, no heat transfer occurs between the gas and the external environment, and since the gas expands freely into container B there is no resistance "pushing" against it, which means no work is done on the gas as it expands. (a) In reaching equilibrium, how much heat transfer occurs from 1.00 kg of water at \(\displaystyle 40.0º C\) when it is placed in contact with 1.00 kg of \(\displaystyle 20.0º C\) water in reaching equilibrium? (b) 0.667 barrels. Explicitly show how you follow the steps in the Problem-Solving Strategies for Thermodynamics. Set 1 - This test comprises of 50 questions on Thermodynamics. The University does not release solutions to past exam questions, but numerical answers are: 2013 (b) Qout=500kJ, max … 63. Explicitly show how you follow the steps in the Problem-Solving Strategies for Entropy. Explain your responses. Solution (b) \(\displaystyle 1.66×10^8J\) or \(\displaystyle 3.97×10^4kcal\) Question #122066. a)Suba (m=72.6 kg) is skiing from a hill. (a) How much food energy will a man metabolize in the process of doing 35.0 kJ of work with an efficiency of 5.00%? (b) \(\displaystyle –8.30 × 10^{12}J\), where the negative sign indicates a reduction in heat transfer to the environment. 83. The first law of thermodynamics and the conservation of energy, as discussed in Conservation of Energy, are clearly related. 15. Specifically, explain what happens to the entropy of its surroundings. Explain, in terms of efficiency, what factors may keep you from realizing your ideal energy use on this trip. 31. (b) What is the cost of doing this if the work costs 10.0 cents per \(\displaystyle 3.60×10^6J \) (one kilowatt-hour)? If her efficiency is 18.0%, how much heat transfer occurs to the environment to keep her temperature constant? 8. 82. A system does \(\displaystyle 1.80×10^8J\) of work while \(\displaystyle 7.50×10^8J\) of heat transfer occurs to the environment. (a) How much heat transfer occurs to the environment by an electrical power station that uses \(\displaystyle 1.25×10^{14}J\) of heat transfer into the engine with an efficiency of 42.0%? The energy content of gasoline is \(\displaystyle 1.3×10^8J/gal\). energy while the water in the tub will have an increase in ? A coal-fired electrical power station has an efficiency of 38%. A hand-driven tire pump has a piston with a 2.50-cm diameter and a maximum stroke of 30.0 cm. 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. The Carnot efficiency is \(\displaystyle Eff_C=1−\frac{T_c}{T_h}=1−\frac{300K}{600K}=0.50\). (c) \(\displaystyle 2.85×10^{10}J/K\) A car tire contains \(\displaystyle 0.0380m^3\) of air at a pressure of \(\displaystyle 2.20×10^5N/m^2\) (about 32 psi). This is the currently selected item. (c) Work done by the motor is \(\displaystyle 1.61×10^7\); thus the motor produces 7.67 times the work done by the man. Do this by considering the number of ways that each could be formed (the number of microstates in each macrostate). (c) This cost seems quite realistic; it says that running an air conditioner all day would cost $9.59 (if it ran continuously). 33. (a) \(\displaystyle W=PΔV=1.76×10^5J\) Hi. 20. What temperature of hot steam must you use? One method of converting heat transfer into doing work is for heat transfer into a gas to take place, which expands, doing work on a piston, as shown in the figure below. Driving up Pike's Peak (a mere 3000-meter climb) should consume a little less than a quart of gas. Disorganized pile make increasingly more energy unavailable to do work, as implied by this.. 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