Quiz

QUIZ

1. According to the first law of thermodynamics, what is the change of internal energy of a system determined by?

a. The net work done by the system b. The net heat output of the system c. The change in its temperature before and after work is done d. The difference between the heat put in and the work output of the system

Answer: d. The change in internal energy of a system is the difference between the heat put in and the work output of the system.

2. What is the internal energy of a given system?

a. The potential energy of the system b. The difference between the potential energy and the kinetic energy of a system c. The sum of the potential energy and the kinetic energy of a system d. The kinetic energy of the system

Answer: c. The internal energy of a given system is the sum of the potential energy and kinetic energy of a system. It is independent of how the energy gets into the system.

3. Which of these biological processes is not considered a one-way energy process in that it is reversible rather than being irreversible?

a. Photosynthesis b. Glucose metabolism c. Fat storage d. Exercise

Answer: c. Fat storage and the loss of fat are reversible processes that change the potential energy of the system. The other biological processes are considered irreversible processes.

4. Under what circumstances in a traditional heat engine will the heat output be zero?

a. When the work output is at its maximum potential b. When the system has low friction c. When the heat input is less than the work output d. There is no situation in a heat engine where the heat output is zero

Answer: d. There is no situation in a heat engine where the heat output is zero. Anytime the heat engine is running there will be some inefficiency and there will be some heat output.

5. According to the second law of thermodynamics, what is the case?

a. Heat always goes from hot to cold areas in a system. b. Heat output will always exceed work output. c. Heat engines are imperfect systems. d. Work output will always exceed heat output.

Answer: a. According to the second law of thermodynamics, heat always goes from hot to cold areas in a system. Heat and work output will be different with different systems with more efficient systems putting out more work than heat but this is not always the case.

6. In a heat engine, the efficiency will be related to what?

a. The work put in minus the work put out. b. The work put out minus the work put in. c. The heat put out minus the heat put in divided by work. d. The work output divided by the heat put in.

Answer: d. Ideally, the work output should be equal to the heat put in so that the efficiency will be 100 percent. The efficiency, however, will be the work output divided by the heat input, which will be less than 100 percent.

7. In a four-stroke engine, what does the intake involve?

a. The increase in pressure when the gas-air mixture is added. b. The decrease in volume when the piston is pressed on. c. The ignition of the spark plugs and increase in pressure. d. The release of gases to the outside.

Answer: a. The intake involves the increase in pressure when the gasair mixture is added to the system. This mixture gets ignited under great pressure after compression, which leads to great power exerted.

8. What happens during the exhaust phase of the four-stroke engine?

a. Q intake is increased. b. Q is held the same. c. Q intake is decreased. d. Q output is increased.

Answer: d. The exhaust portion of the four-stroke engine happens at the same time as the intake phase but actually involves the output of heat in the release of exhaust from the engine. The intake of gas is at a colder temperature but, because this is not ignited, the intake part adds to the potential energy of the system and not to the Q intake.

9. What example represents a Carnot engine?

a. A nuclear reactor b. A propane-powered engine c. A diesel-powered engine d. None of these is a Carnot engine

Answer: d. A Carnot engine is just a theoretical engine that has only reversible processes. These types of processes cannot be reversible and heat will be lost so that heat energy must continually be added in order to drive the engine.

10. Under what conditions does a heat pump work better to heat indoor air when compared to the outdoor air?

a. When the temperature difference isn’t very great. b. When the fuel system involved is propane versus gasoline. c. When the outdoor air temperature is at its lowest. d. When there is a great difference between the outdoor temperature and the indoor temperature.

Answer: a. These heat pumps work better to heat the indoor air when there is a limited difference between the indoor temperature and the outdoor temperature.