3) a Hydroelectric Dam Has a Head of 75M
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Physics 207 Exam #3 Spring 2005
Name:______1) What two regions of the United States have the largest concentrations of hydroelectric dams? (2 ponts)
2) Approximately what percentage of electricity generated in the United States comes from hydroelectricity? (2 points)
3) A hydroelectric dam has a head of 75m. a) How much potential energy is converted into kinetic energy when 1liter of water falls through the dam? (Hint: 1 liter of water has a mass of 1 kg.) (2 points)
b) If the turbines convert the kinetic energy of the water into electricity with an efficiency of 85%, how much electricity can we generate with a flow of 50,000 liters/second? ( 3 points)
4) What State has the highest potential for wind energy when factoring in such things as environmental and land use restrictions? (2 points)
5) What country is currently the world leader in the production of wind energy? (2 points)
6) Approximately what percentage of the total US electricity production would it be desirable to have come from wind power? (2 points) 7) A particular wind turbine is rated at 10,000 W when the wind is blowing at 20 mi/hr. How much power would we expect it to generate when the wind speed is only 10 mi/hr? (4 points)
8) Approximately what percentage of the sun’s energy that reached the earth’s surface is converted into wind energy? (2 points)
9) An Ocean Thermal Energy Conversion (OTEC) plant is being designed to operate in the tropics where the surface temperature is 22C and the deep water temperature is 2C. What is the maximum theoretical efficiency of the plant? (4 points)
10) The Bay of Fundy has tidal the largest tidal variations in the world at 53 ft. These large variations make it a potentially attractive location to place a tidal energy plant. Where is the Bay of Fundy located. (2 points)
11) Burning garbage is one potential source of electricity that has been developed in some communities. How does the energy content in garbage compare to the energy content is good coal? (2 points)
12) Ethanol is a biomass fuel that is of particular interest in Illinois. In the list below, place an E on the line if it describes Ethanol or a G on the line if it describes Gasoline. ( 1 pt. each) ______Higher Octane Rating
______Higher energy content per gallon.
______Less expensive per gallon.
______Cleaner burning
______More corrosive 13) What is meant by the term solar insolation? (2 points)
14) The solar constant, i.e. the power density coming from the sun at the location of the earth, is 2 2cal/mincm . The power density averaged over the surface of the earth during the course of a day is only about 0.25cal/mincm2. What causes the difference in the two numbers. (Hint there are three separate effects that each reduce the average by a factor of 2.) (3 points)
15) What is the difference between an active and a passive solar heating system? (3 points)
16) In the United States, (or anywhere else in the Northern Hemisphere) which way should we face a stationary solar collector (North, South, East or West) (2 points)
17) In class, we discussed two basic methods for using solar energy to generate electricity. Give a brief description of each. (4 points)
18) As a general rule, a watt of electricity generated using photovoltaic cells cost more than a watt of electricity generated using more traditional techniques, (i.e. coal/nuclear/hydro). What kinds of situations make it economically favorable to use photovoltaic cells. (2 points) 19) What is the difference between Fusion and Fission. (4 points)
20) During the course of a year, a 1GW power plant produces 9.51016J of energy. If this energy is produced by nuclear fission, how many kilograms of mass is converted into energy (3 points)
21) What is the dominant source of radiation that most people will be exposed to during the course of their lives? (2 points)
22) What is the difference between an isotope and an ion? (2 points)
23) For heavy elements, i.e. those with Z>20, what is generally true about the number of neutrons as compared to the number of protons in the nucleus? (2 points)
24) Strontium 90 has a half-life of approximately 30 years. If we start out with 1 curie of Strontium 90, how many curies would be left after 300 years? (4 points) 25) What are the two major roles of water in the operation of US nuclear reactors? (4 points)
26) What are the two major roles of the Uranium in the operation of US nuclear reactors? (3 points)
27) What is the function of the control rods in a nuclear reactor? (2 points)
28) It is probable that a long term storage facility for high level nuclear waste will be built in the tuff (a type of volcanic rock) in Yucca Mountain. What state is Yucca Mountain located in. (2 points)
29) According to our discussions in class, approximately how long should radioactive waste be stored in order that the majority of the radioactivity has dissipated? ( 2 points)
30) What state has the largest number of nuclear power plants within its boarders? ( 2 points) 31) Approximately what percentage of the electricity generated in the Illinois comes from nuclear power? (2 points)
32) Why is it impossible for a nuclear reactor to explode like a nuclear bomb? ( 2 points)
235 33) If 92U undergoes an alpha decay, what is the atomic mass and the atomic number of the new atom? (4 points)
137 34) If 55Cs undergoes a beta minus decay, what is the atomic mass and the atomic number of the new atom? (4 points)
35) On the lines below, indicate which type of radiation (alpha, beta, gamma) that is described. ( 1 points each)
_____ same as a Helium nucleus
_____same as an electron
_____ high energy electromagnetic radiation
_____ most penetrating type of radiation
_____ highest Quality Factor when measuring radiation amounts in units of rems _____ least penetrating type of radiation Potentially Useful Equations
Doubling time Thermal Energy 70% Q mCT DT rate
Newton’s 2nd Law If we know Fahrenheit and want Celsius F ma 5 C F 32 9 Definition of momentum If we know Celsius and want Fahrenheit p mv 9 F C 32 5 Kinetic Energy If we know Celsius and want Kelvin 1 K C 273 KE mv 2 2
Gravitational Potential Energy Conservation of Energy PE mgh KE PE const.
If constant acceleration Electric Currents, Power, Voltage Resistance v at V IR 1 x at 2 P IV 2 P I 2 R Heat Engine Forces on cars
QH Qc W Fa ma W F mgs e h QH Fr C r mv
Qc 1 2 e 1 Fad CD Af v QH 370
TC ecarnt 1 TH
Light and Waves Radioactive Decay c ( frequncy)x(wavelength) A A4 4 (alpha)Z X z2Y 2 4 P eAT A A 0 (beta)Z X Z1Y 1 mT 2900m K 8 A A 0 c 3x10 m / s (beta)Z X Z1Y 1
A * A 0 (gamma)Z X Z X 0 Wind Power P const. v3 E mc2