An engine is designed to obtain energy from the temperature gradient of the ocean. What is the thermodynamic efficiency of such an engine if the temperature of the surface of the water is 59°F (15°C) and the temperature well below the surface is 41°F (5°C)?
a. 3.5%
b. 67%
c. 31%
d. 17%
e. 96%
A
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Unpolarized light passes through three ideal polarizing filters. The first filter is oriented with a horizontal transmission axis, the second one has its transmission axis at 30° from the horizontal,
and the third filter has a vertical transmission axis. What percent of the light gets through this combination? A) 9.4% B) 91% C) 50% D) 0% E) 33%
Where is the sun located relative to a planet's orbit about it?
a. at the center of the orbit, which is a circle b. at the center of the orbit, which is an ellipse c. at one focus of the ellipse which forms the orbit d. none of the above
According to modern science, what was the approximate chemical composition of the solar nebula?
A) 98% hydrogen and helium, 2% everything else B) 50% hydrogen and helium, 50% everything else C) 98% hydrogen, 2% helium D) roughly equal proportions of hydrogen, helium, water, and methane
Which of the following is the best answer to the question "Why does the Sun shine?"
A) The Sun initially began generating energy through nuclear fusion as it formed, but today, it generates energy primarily through the sunspot cycle. B) The young Sun became hotter through gravitational contraction. Once the core was hot enough, nuclear fusion began and has kept the Sun shining ever since. C) The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur. D) As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.