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The following physics responses are provided by a student and, as such, should be considered in that context. While every effort is made for accuracy, absolute correctness cannot be fully guaranteed.
| C | I | Question | Answer |
|---|---|---|---|
| 12 | A system is acted on by its surroundings in such a way that it receives 50 J of heat while simultaneously doing 20 J of work. What is its net change in internal energy? | 30 J | |
| 12 | A thermodynamic process that happens very quickly tends to be: | adiabatic. | |
| 12 | A turbine takes in 1000-K steam and exhausts the steam at a temperature of 500 K. What is the maximum theoretical efficiency of this system? | 50% | |
| 12 | According to the first law of thermodynamics, for any process that may occur within an isolated system, which of the following choices applies? 1) entropy remains constant 2) entropy increases 3) entropy decreases 4) None of the above choices apply. | 4) None of the above choices apply. | |
| 12 | According to the first law of thermodynamics, the sum of the heat gained by a system and the work done on that same system is equivalent to which of the following? 1) entropy change 2) internal energy change 3) temperature change 4) specific heat 5) both choices A and B are valid. | internal energy change | |
| 12 | According to the second law of thermodynamics, which of the following applies to the heat received from a high temperature reservoir by a heat engine operating in a complete cycle? 1) must be completely converted to work 2) equals the entropy increase 3) converted completely into internal energy 4) cannot be completely converted to work 5) equals the entropy decrease | cannot be completely converted to work | |
| 12 | An 800-MW electric power plant has an efficiency of 30%. It loses its waste heat in large cooling towers. Approximately how much waste heat (in MJ) is discharged to the atmosphere per second? | 1900 MJ | |
| 12 | An adiabatic expansion refers to the fact that: 1) no heat is transferred between a system and its surroundings. 2) the pressure remains constant. 3) the temperature remains constant. 4) the volume remains constant. 5) both choices A and B are valid. | no heat is transferred between a system and its surroundings. | |
| 12 | An avalanche of ice and snow of mass 1 800 kg slides a vertical distance of 160 m down a mountainside. If the temperature of the ice, snow, mountain and surrounding air are all at 0°C, what is the change in entropy of the universe? | 10000 J/K | |
| 12 | An electrical generating plant operates at a boiler temperature of 220°C and exhausts the unused heat into a nearby river at 18°C. What is the maximum theoretical efficiency of the plant? (0°C = 273 K) | 41% | |
| 12 | An electrical generating plant operates at a boiler temperature of 220°C and exhausts the unused heat into a nearby river at 19°C. If the generating plant has a power output of 800 megawatts (MW) and if the actual efficiency is 3/4 the theoretical efficiency, how much heat per second must be delivered to the boiler? (0°C = 273 K) | 2620 MW | |
| 12 | An electrical power plant manages to send 88% of the heat produced in the burning of fossil fuel into the water-to-steam conversion. Of the heat carried by the steam, 40% is converted to the mechanical energy of the spinning turbine. Which of the following choices best describes the overall efficiency of the heat-to-work conversion in the plant (as a percentage)? 1) greater than 88% 2) 64% 3) less than 40% 4) 40% 5) 53% | less than 40% | |
| 12 | An ideal gas at pressure, volume, and temperature, P0, V0, and T0, respectively, is heated to point A, allowed to expand to point B also at A's temperature 2T0, and then returned to the original condition. The internal energy decreases by 3P0V0/2 going from point B to point T0. How much heat left the gas from point B to point T0? 1) 0 2) P0V0/2 3) 3P0V0/2 4) 5P0V0/2 5) 3 P0V0 | 5P0V0/25P0V0/2 | |
| 12 | An ideal gas at pressure, volume, and temperature, P0, V0, and T0, respectively, is heated to point A, allowed to expand to point B also at A's temperature 2T0, and then returned to the original condition. The internal energy decreases by 3P0V0/2 going from point B to point T0. In going around this cycle once, which quantity equals zero?An ideal gas at pressure, volume, and temperature, P0, V0, and T0, respectively, is heated to point A, allowed to expand to point B also at A's temperature 2T0, and then returned to the original condition. The internal energy decreases by 3P0V0/2 going from point B to point T0. In going around this cycle once, which quantity equals zero? 1) the net change in internal energy of the gas 2) the net work done by the gas 3) the net heat added to the gas 4) All three are zero. 5) None of the above. | the net change in internal energy of the gas | |
| 12 | An ideal gas at pressure, volume, and temperature, P0, V0, and T0, respectively, is heated to point A, allowed to expand to point B also at A's temperature 2T0, and then returned to the original condition. The internal energy increases by 3P0V0/2 going from point T0 to point A. How much heat entered the gas from point T0 to point A? | 3 P0V0/2 |
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