Chapter 15: 20Q (page 412)
Question: Living organisms, as they grow, convert relatively simple food molecules into complex structures. Is this a violation of the second law of thermodynamics? Explain your answer.
No, this is not a violation of the second law of thermodynamics.
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Question: (I) The low temperature of a freezer cooling coil is\({\bf{ - 8^\circ C}}\)and the discharge temperature is\({\bf{33^\circ C}}\). What is the maximum theoretical coefficient of performance?
It has been suggested that a heat engine could be developed that made use of the temperature difference between water at the surface of the ocean and water several hundred meters deep. In the tropics, the temperatures may be 27°C and 4°C, respectively.
(a) What is the maximum efficiency such an engine could have?
(b) Why might such an engine be feasible in spite of the low efficiency?
(c) Can you imagine any adverse environmental effects that might occur?
A Carnot engine operates with\({T_L} = {\bf{20^\circ C}}\)and has an efficiency of 25%. By how many kelvins should the high operating temperature\({T_H}\)be increased to achieve an efficiency of 35%?
Question: Which is possible: converting (i) 100 J of work entirely into 100 J of heat, (ii) 100 J of heat entirely into 100 J of work?
(a) Only (i) is possible.
(b) Only (ii) is possible.
(c) Both (i) and (ii) are possible.
(d) Neither (i) nor (ii) is possible.
(I) An ideal gas expands isothermally, performing\({\bf{4}}{\bf{.30 \times 1}}{{\bf{0}}^{\bf{3}}}\;{\bf{J}}\) of work in the process. Calculate (a) the change in internal energy of the gas, and (b) the heat absorbed during this expansion.
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