The device shown in Figure CQ22.7, called a thermoelectric converter, uses a series of semiconductor cells to transform internal energy to electric potential energy, which we will study in Chapter 25. In the photograph on the left, both legs of the device are at the same temperature and no electric potential energy is produced. When one leg is at a higher temperature than the other as shown in the photograph on the right, however, electric potential energy is produced as the device extracts energy from the hot reservoir and drives a small electric motor. (a) Why is the difference in temperature necessary to produce electric potential energy in this demonstration? (b) In what sense does this intriguing experiment demonstrate the second law of thermodynamics ?
The device shown in Figure CQ22.7, called a thermoelectric converter, uses a series of semiconductor cells to transform internal energy to electric potential energy, which we will study in Chapter 25. In the photograph on the left, both legs of the device are at the same temperature and no electric potential energy is produced. When one leg is at a higher temperature than the other as shown in the photograph on the right, however, electric potential energy is produced as the device extracts energy from the hot reservoir and drives a small electric motor. (a) Why is the difference in temperature necessary to produce electric potential energy in this demonstration? (b) In what sense does this intriguing experiment demonstrate the second law of thermodynamics ?
Solution Summary: The author explains the second law of thermodynamics, which states that heat flows from high temperature to law temperature, and the direction of the potential difference changes with the change in energy flow.
The device shown in Figure CQ22.7, called a thermoelectric converter, uses a series of semiconductor cells to transform internal energy to electric potential energy, which we will study in Chapter 25. In the photograph on the left, both legs of the device are at the same temperature and no electric potential energy is produced. When one leg is at a higher temperature than the other as shown in the photograph on the right, however, electric potential energy is produced as the device extracts energy from the hot reservoir and drives a small electric motor. (a) Why is the difference in temperature necessary to produce electric potential energy in this demonstration? (b) In what sense does this intriguing experiment demonstrate the second law of thermodynamics?
Science that deals with the amount of energy transferred from one equilibrium state to another equilibrium state.
At a certain location, the solar power per unit area reaching Earth's surface is 200 W/ m^2, averaged over a 24-hour day. If the average power requirement in your home is 3 kW and you can convert solar power to electric power with 10 % efficiency, how large a collector area will you need to meet all your household energy requirements from solar energy? (Will a collector fit in your yard or on your roof? ).
An electric hot plate raises its own internal energy and the internal energy of a cup of water by 15000 J, and there is at the same time
2900 J transferred to the cooler air (that is, Q = -2900 J). How much energy was transferred to the hot plate in the form of
electricity?
electric energy input =
i
Question 7: Certain areas in Arizona, Nevada, California and Texas can have up to 4000 sunny hours a
year. The fact that these vast lands are less populated and agriculturally not suitable makes them ideal
for solar power plants. Though most commercial solar panels have efficiencies from 15% to 20%,
researchers have now developed solar cells with efficiencies approaching 50%. If you are asked to plant
a solar energy system in these areas using the newest technology, how much land do you need to
produce enough energy for the US.
Make the conservative assumptions that the average light energy landing to the Earth' surface is 1.0
cal/(cm2 min).
An estimate for the US energy consumption by major sources is given below.
U.S. primary energy consumption by major sources, 1950-2019
quadrillion British thermal units
110
100
90
80
70
60
50
40
30
20
10
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
renewables
nuclear
petroleum
natural gas
coal
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