Good photovoltaic cells have an efficiency of approximately ________

Good photovoltaic cells have an efficiency of approximately ________ Question 1 options: a) 2-6%
b) 28-38%
c) 14-17%
d) 38-58% Save Question 2 (1 point)
Hydroelectric power in the U.S. currently represents about ______ % of the total U.S. electricity. Question 2 options:
a) less than 1 b) 40 c) 1 d) 7 Save Question 3 (1 point)
A windmill system which produces 9 kW of electrical power when the wind is blowing at 4 m/s, will produce ______ kilowatts when the wind is blowing 8 m/s? Question 3 options:
a) 72
b) 36
c) 24 d)
18 Save Question 4 (1 point)
Radioactivity refers to ________. Question 4 options: a) conversion of mass within the nucleus to energy b) decay of nuclei induced with neutrons
c) thespontanious decay of atomic nuclei into lighter, more stable nuclei d) decay of nuclei which must involve a neutrino or an antineutrino Save Question 5 (1 point)
The Solar Constant, 2 calories per square centimeter per minute, is _______. Question 5 options: a) the average solar intensity at ground level
b) the annual amount of solar energy available at the top of the earth’s atmophere c) the solar power density at 93 million miles from the sun d) extremely variable Save Question 6 (1 point)
In 2003 the wind energy generating capacity in the U.S. was about _______. Question 6 options:
a) 6.4 GW
b) 6.4 MW
c) 6.4 kW
d) 6.4 TW Save Question 7 (1 point)
The spectrum of solar radiation above the earth’s atmosphere has its maximum in intensity _______. Question 7 options:
a) at a wavelength higher than does the spectrum reaching the surface of the earth
b) at the same wavelength as does the spectrum reaching the surface of the earth
c) at a wavelength lower than does the spectrum reaching the surface of the earth
d) is not related to the maximum in the spectrum reaching the surface of the earth Save Question 8 (1 point)
Your cottage foundation is made up of 800 cubic feet of concrete while the floor is made up of 200 cubic feet of oak. About how many Btu are required to raise the temperature of the foundation and floor by 30 degrees F? Given: 22 Btu per cubic feet per degree F for concrete and 25 Btu per cubic feet per degree F for wood. Question 8 options: a) 678,000 b) 150,000 c) 528,000
d) 1,500,000 Save Question 9 (1 point)
What is a thermal neutron? Question 9 options: a) a neutron with kinetic energy about 1/40 of an eV. b) a neutron with a kinetic energy about 5 MeV
c) one of the neutrons which is produced in a typical nuclear fission reaction d) a neutron inside any large nucleus Save
Question 10 (1 point)
Suppose you have a typical flat-plate solar collector with area 64 square feet. What is a reasonable number for the Btu per day collected as heat energy? Assume an efficiency of 50%. Question 10 options:
a) 8,000
b) 64,000
c) 16,000
d) 32,000 Save Question 11 (1 point)
About _______ % of the total energy consumed in the U.S. each year is currently supplied by solar energy. Recall that we use about 98 QBtu per year. Question 11 options: a) 10 b) 6
c) 0.06 d) 1 Save Question 12 (1 point)
What is the base material and the doping material typically used in photovoltaic cells to convert solar radiation into electrical energy? Question 12 options: a) silicon doped with uranium
b) carbon doped with hydrogen c) silicon doped with arsenic
d) antimony doped with silicon
Save Question 13 (1 point)
What is the typical size and voltage output of an individual solar cell? Question 13 options:
a) 2 inches diameter and about 0.5 volt b) 6 inches diameter and about 1 volt
c) 0.5 inch diameter and about 9 volts
d) 1 inch diameter and about 0.1 volts Save Question 14 (1 point)
A parabolic reflector ________ Question 14 options: a) focuses only the direct component of sunlight b) focuses only the diffuse component of sunlight c) focuses both the direct and diffuse components of sunlight
d) can be used for solare collection systems only if the overall efficiency is less than 5 % Save Question 15 (1 point)
The temperature of the surface of the sun is about 5800 K. Using Stefan’s law, find the power per unit area emitted by the sun assuming that the surface emissivity is ideal, i.e. epsilon=1. Question 15 options:
a) 16 MW/square meter
b) 64 MW/square meter
c) 100 MW/square meter
d) 6.4 GW/square meter Save