final physics
Which of the following is a "secondary pollutant" produced by photochemical reactions with primary pollutants?
Ozone The others come straight out of the tailpipe. Ozone is a result of sunlight reacting with NO2.
A cyclone device is used to remove what type of pollution from the exhaust of a fossil fuel plant?
Particulates
Which is a more energy efficient way to heat a home?
Passive solar heating is more efficient than using solar photovoltaic cells. Solar PV cells have only 15-20% efficiency in converting solar energy into electricity, and then that electricity would have to be used to power a heater which would also involve some losses. However, with passive solar heating, virtually 100% of the solar energy is used to heat something up.
Warming of the Earth causes ice to melt. Liquid water has a lower albedo than ice. What kind of feedback effect on the climate does melting ice have?
Positive feedback Warmer makes it darker which makes it warmer which makes it darker.
Consider the amount of electrical energy used by a typical home that gets its electricity from a standard fossil-fuel power generator. Is that energy greater using end-use accounting, or primary energy accounting?
Primary energy accounting The amount of energy that makes it to end use from a standard power generator is less than the amount of energy in the fuel (primary energy) going into the generator.
Which of the following is responsible for producing acid rain?
SO2 It forms sulfuric acid droplets. CO2, which occurs naturally, also makes rain acidic. NO compounds also make rain acidic, but I did not include that in the list of options.
Ethanol can be derived from multiple plant sources. Which of these has the largest net energy gain (energy in the ethanol divided by the amount of energy needed to produce it)?
Sugar Cane
(T/F) A solar photovoltaic system generates electricity by individual photons causing electrons to flow through a circuit.
TRUE
(T/F) X-rays, visible light, and radio waves are all forms of light that have different frequencies.
TRUE
(T/F) When a Uranium nucleus splits, the sum of the masses of everything it splits into is less than the mass of the original nucleus.
TRUE That's where the nuclear energy is stored. The reduction in mass is accompanied by a release in energy given by E=mc^2 where m is the amount of mass converted to energy.
How has Earth's global temperature varied over the history of the planet?
The Earth's global temperature has changed a lot, including some rapid changes and some long periods of time with minimal changes.
The specific heat capacity of liquid water is 4,184 J/kg/K, and the specific heat capacity of water ice is 2,030 J/kg/K. If the same amount of energy is put into 1 kg of water ice at 200 K and into 1 kg of liquid water at 300 K, which one will have a greater change of temperature? Assume there are no state changes.
The water ice Liquid water has a higher specific heat capacity. It takes over 4000 J to change the temperature of a kg of water by 1 K, but it only takes about 2000 J to change the temperature of a kg of ice by 1 K. So if I put 4000 J into each, the water will heat by about 1 K, while the ice will heat up by 2 K.
Why is acid rain more prevalent in the northeastern part of the United States?
There are more coal-burning power plants in the northeast and midwest whose exhaust blows into the northeast.
An electric power generator in a nuclear plant works by
Using the heat energy from radioactive decay products to boil water and produce steam to turn a generator.
Which would make a better thermal insulating material?
Water, with a thermal conductivity of 0.6 W/m/K. Thermal conductivity is a measure of how fast energy is conducted through a material, so to insulate we don't want energy conducted quickly, but slowly, so we want a smaller conductivity.
A pumped storage facility stores energy by pumping water to a reservoir at some height above a generator. What is the energy density in Megajoules per kilogram for water stored at a height of 200 m? 1 Megajoule = 106joules
0.00196 Energy = m*g*h, where in this case h = 200m and m = 1 kg. g = 9.8 m/s^2 on Earth. That gives 200*1*9.8 = 1960J= 0.00196 MJ.
The nuclear advantage refers to the greater amount of energy available from nuclear fission per kg of fuel compared to that available from burning fossil fuels. Roughly how many times more fuel comes from a kg of Uranium compared to a kg of coal?
10 million This is the ratio of the energy per kg available from nuclear fission divided by the energy per kg available from burning coal or any other fossil fuel
If our energy consumption grows at a modest rate of 2% each year, how many years will it take for our energy consumption to double from its current amount?
35 years You can work this out in detail using the equation at the end of the test, or you could remember that the time to double is 70 divided by the growth rate. 70/2 = 35.
Consider two solar heating systems. In system A, pipes are run across the roof of a house in a glass enclosure with a black backing with an antifreeze solution flowing through the pipes. The fluid is then run through pipes surrounded by water, heating the water through conduction. In system B, water runs through pipes across the roof without any enclosure and is heated directly by the Sun. Which system gives hotter water?
A System A is active heating that prevents heat from leaving the system and lets the fluid get hotter.
Which of the following has more energy?
A photon of violet light. The shortest wavelength has the most energy.
Which of the following slabs would make a better insulator, assuming they all have the same surface area, but different thicknesses as indicated in the question.
A piece of wood(k=0.11) 8 inches thick. The R-value of a piece of insulation tells us how good an insulator it is, and R=d/k. Calculate d/k for each selection.
Hubbert's Peak, sometimes referred to as Peak Oil, refers to the time when world production of oil (extraction from the ground) reaches a peak value. At that time, what fraction of the world's oil reserves will have been used?
About half
An electric power generator in a fossil fuel plant works by
Boiling water, and using the steam to turn many loops of wire in the presence of a strong magnetic field, generating current in the wire.
Which of the following is a more efficient use of energy to heat a building?
Bringing natural gas into the building and burning it to heat water that is piped through radiators in the building. Using electricity to make heat is very inefficient because that electricity had to be produced in an inefficient process in the first place in a power plant. So it wastes energy to use thermal energy to make "high quality energy"and then just turn that high quality energy around to make low quality thermal energy.
Catalytic converters reduce the amount of what pollutant in car exhaust?
CO Catalytic converters cause CO to react with oxygen in the atmosphere to form CO2.
What gas is an inevitable product of burning a fossil fuel?
CO2 Burning something means to chemically react oxygen with it. Fossil fuels are hydrocarbons made of carbon and hydrogen, and when they react with water they produce CO2 and H2O. CO can also be produced, but that is incomplete combustion. The others are produced due to contaminants in the fuel, but would not be produced with a pure hydrocarbon fuel.
What does a transformer do? This question could have more than one correct answer. Bubble in all correct answers to receive credit.
Changes the voltage in a circuit Changes the current in a circuit
What type of fuel leads to more acid rain?
Coal Sulfur is an abundant contaminant in coal.
Any warm opaque object (such as a person, a planet, or an incandescent light bulb filament) emits what kind of light spectrum?
Continuous (all colors)
Which type of engine has a greater thermodynamic efficiency
Diesel automobile engine Diesel engines operate at higher temperatures, so they have a greater thermodynamic efficiency. That's the reason anyone would want to use them. But they produce more particulate pollutants, are noisy, and are heavier.
Consider two atomic nuclei, A and B. A has 92 protons and 146 neutrons, while B has 94 protons and 150 neutrons?A and B are
Different elements.
Which is the greater supply of energy?
Direct solar energy (converting sunlight to electricity through photovoltaics or solar thermal plants).
How much more power is available from wind when the wind speed doubles? Ignore any changes in windmill efficiency with different wind speed for this question.
Eight times as much
Solar concentrating power plants are used to make
Electricity The term "power plant"gives it away. These concentrate sunlight to make temperatures high enough to boil water, and once you do that you can have steam turn a turbine to turn a generator and make electricity.
(T/F) Most of the energy from the Sun that hits the Earth goes into photosynthesis by plants and algae, providing biomass energy.
FALSE
(T/F) The largest single source of radiation on people in the United States is radioactive waste from nuclear power plants.
FALSE
(T/F) Typical efficiencies for solar photovoltaic panels to convert sunlight hitting them into electricity are less than 1%.
FALSE Efficiencies are typically 10-20%.
(T/F) It's theoretically possible to make a windmill that extracts 90% of the energy from the wind.
FALSE Highest efficiency is 59%.
(T/F) Hydroelectric power plants run at about the same efficiency as coal-fired and natural gas-fired plants
FALSE Hydroelectric power plants are converting gravitational potential energy (water up high) into kinetic energy (water moving through a turbine) and then into electricity. Coal-fired and natural-gas-fired plants have to convert thermal energy (burning fossil fuel to heat water to make steam) into kinetic energy (steam turns turbine) and then into electricity. Converting thermal energy has a theoretical limit on efficiency that means they are much less efficient than the other which has no theoretical limit.
(T/F) The Earth's atmosphere has had a fairly constant concentration of Oxygen since the planet formed.
FALSE Oxygen started rising only a couple of billion years ago after respiration by bacteria for more than a billion years.
The Earth's climate has been basically constant over the history of the solar system, with a gradual warming as the Sun has gotten gradually brighter.
FALSE The climate has changed dramatically on multiple occasions in the past.
(T/F) Natural variations in the output of the Sun due to sunspots and the Sun's natural 11-year solar cycle results in a fluctuation of energy input to the Earth that is about as large as the warming effect of carbon dioxide.
FALSE The current amount of forcing from CO2 is about 2 W/m^2. The forcing due to solar variations is a fraction of 1 W/m^2.
(T/F) Although the current level of CO2 in the atmosphere is higher than it was 100 years ago, it has been this high several times in the last 100 thousand years.
FALSE The last time it was this high was several million years ago.
(T/F) The maximum efficiency of a windmill is about the same as that of a hydroelectric power plant.
FALSE The maximum efficiency of a windmill is 59%. This is because the air must still be moving when it passes through the windmill. While hydroelectric power also comes from kinetic energy of a flowing substance through a mill (water instead of air, but the principle is the same), but for a hydroelectric plant, the water's kinetic energy is supplied by the gravitational potential energy of the water behind the dam. It is essentially falling through the turbine, so virtually 100% of that gravitational potential energy can be extracted. The water is actually flowing slowly on both sides, but is being pushed through by the weight of the water above it. For wind, it is blowing and its kinetic energy is removed by the windmill. If 100% of the energy were removed by the windmill, the air would literally stop and that would mean there is no room for the new wind to move into!
(T/F) If we could eliminate friction, we could make a power plant that is 100% efficient. However, we can never totally eliminate friction.
FALSE The second law of thermodynamics states that there is a fundamental limit on efficiency based on the temperature of the cold side of a power plant.
(T/F) Due to radiation and various accidents at nuclear power plants, nuclear power plants are responsible for more deaths per unit of energy generated than fossil fuel power plants.
FALSE There have been more deaths from fossil fuel mining, transportation and pollution than from nuclear power plants.
(T/F) The power output of a windmill is always the highest when the wind is blowing fastest, as long as it is below the "cut-out speed" for the windmill (the speed when it is too fast for the windmill to safely operate).
FALSE There is a peak output at the rated speed, and it is lower at all other speeds. There's a figure in the book showing this.
(T/F) A solar thermal concentrator generates electricity by individual photons causing electrons to flow through a circuit.
FALSE This time of primary solar electric generator heats a substance using sunlight, making it heat water to produce steam and drive a turbine, just like a fossil fuel plant, but using sunlight for heat instead of coal fire.
(T/F) If you start with a block of water ice at -50 degrees C and apply heat to it at a constant rate, its temperature will rise at a constant rate as long as you continue heating it.
FALSE When it reaches 0 C the temperature will stop increasing and energy instead will go into melting the ice.
(T/F) The Earth currently has a negligible warming (less than 10 Kelvins) greenhouse effect.
FALSE Current greenhouse warming on Earth is about 33C = 33K. See the table in the book on greenhouse effect on Mars, Venus and Earth.
(T/F) Nuclear power plants produce just as much CO2 as fossil fuel power plants per unit of energy generated
FALSE Nuclear power plants don't burn anything chemically, so zero CO2 is produced.
What conditions lead to the build up of smog in urban areas
Increasing atmospheric temperature with altitude that inhibits convection
What is the main reason Venus is so much warmer than the Earth?
It has a thick atmosphere of carbon dioxide It has a very large greenhouse effect, much larger than the effect of its distance from the Sun.
What is special about a greenhouse gas molecule that makes it a greenhouse gas?
It has more than one type of atom in it and has lots of vibrational and rotational energy states to absorb infrared radiation.
A block is given a shove so that it slides across the horizontal floor. When it first starts moving it has kinetic energy, but then it slows to a stop. What happened to that kinetic energy?
It was converted to thermal energy by work done on the box by the force of friction. The natural state for the box is to keep moving at a constant speed (Newton's first law), and a force is required to make it stop. That force is friction. A force acting on something does work which changes the energy. The box initially has kinetic energy, but after it stops it does not have kinetic energy. It has been converted to thermal energy (heat).
Which of the following statements does not make physical sense?
My house uses 10 kW every day, on average. Kilowatts are a unit of power, measuring the rate of energy usage. Statement B would be akin to saying "I drive 30 miles per hour every hour."40 kWh is an amount of energy, so statement A makes sense. 150 W is power, or a rate of energy usage, so statement C makes sense. Chocolate cake has stored chemical potential energy, and 10 minutes gives a time range for consuming that energy, so that could conceivably be a rate of 10 kW, an amount of power.
How do we get gasoline?
Oil is super-heated producing vapor, and gasoline condenses out of that vapor
To sustain a nuclear chain reaction in a nuclear fission power plant, the splitting of each nucleus of uranium must produce .
On average one neutron that strikes another uranium nucleus. If there's more than one neutron causing a split, then there is a runaway reaction leading to a nuclear explosion.
Considering a concentrating thermal power plant, what type of material would be best as a heat transfer fluid?
One with a high heat capacity. A fluid is needed that can store a lot of energy per kg so that it takes it a long time to cool off. That's what heat capacity measures.
The specific heat capacity of granite is 840 J/kg/K, and the specific heat capacity of concrete is 880 J/kg/K. Assuming you have one slab of each, and each one absorbs the same amount of energy from sunlight shining through the window each day, and each slab has the same mass, which one would get hotter (higher temperature) over the course of a day?
granite If they both have the same mass and get the same amount of energy, then the granite will get hotter: it only takes 840 J to heat up one kg of granite by 1K, for example, but it takes 880 J to heat up one kg of concrete by 1K.
Most of the radiated energy from the Earth to space is in what part of the electromagnetic spectrum?
infrared
The Earth's atmosphere radiates energy primarily in what part of the spectrum?
infrared
The Earth's surface radiates energy primarily in what part of the spectrum?
infrared
Evapotranspiration refers to the energy needed to evaporate water from the oceans and also evaporating from plants that pull the water from the ground through their roots. What would happen to the temperature of the Earth if evapotranspiration did not occur?
it would rise If less energy leaves the Earth by this process, then that energy is still in the planet causing it to reach a higher equilibrium temperature.
Which of the following is not a unit of energy?
watt A Watt is a unit of power (1 Joule/second).
