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When the sun is high in the sky, it delivers approximately
Chapter 3, Problem 13P(choose chapter or problem)
Problem 13P
When the sun is high in the sky, it delivers approximately 1000 watts of power to each square meter of earth’s surface. The temperature of the surface of the sun is about 6000 K, while that of the earth is about 300 K.
(a) Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth.
(b) Suppose you plant grass on this square meter of earth. Some people might argue that the growth of the grass (or of any other living thing) violates the second law of thermodynamics, because disorderly nutrients are converted into an orderly life form. How would you respond?
Questions & Answers
QUESTION:
Problem 13P
When the sun is high in the sky, it delivers approximately 1000 watts of power to each square meter of earth’s surface. The temperature of the surface of the sun is about 6000 K, while that of the earth is about 300 K.
(a) Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth.
(b) Suppose you plant grass on this square meter of earth. Some people might argue that the growth of the grass (or of any other living thing) violates the second law of thermodynamics, because disorderly nutrients are converted into an orderly life form. How would you respond?
ANSWER:
Solution to 13P
Step 1
We need to find the entropy created in one year by the flow of solar heat onto 1 square meter of the earth.
The maximum solar flux entering the earth is 1361W/m2
1 year=365x24x60=5.256x105s
Consider that the solar energy is maximum during the day time, thus the time period at which the earth receives solar energy is,
Time =0.5x5.256x105s=2.628x105s
Surface temperature of earth=300K
Total energy received by earth in one year
Q=2.628x105sx 1361=3.57x108J