638_Physics ProblemsTechnical Physics

# 638_Physics ProblemsTechnical Physics - 640 P22.21 Heat...

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640 Heat Engines, Entropy, and the Second Law of Thermodynamics P22.21 For the Carnot engine, e T T c c h =− =− = 11 300 0600 K 750 K .. Also, e W Q c h = eng . so Q W e h c === eng J J 150 250 . . and QQW ch =− = = eng J J 250 150 100 . FIG. P22.21 (a) Q W e h S eng J 0.700 J 150 214 = = eng J J 214 150 64 3 . (b) Q h , . net J J =−= 214 250 35 7 Q c , net J J = 64 3 100 35 7 The net flow of energy by heat from the cold to the hot reservoir without work input, is impossible. FIG. P22.21(b) (c) For engine S : W e W S = eng eng eng . so W Q c e S eng J J = = = 0700 1 100 1 233 . . and QQ W hc =+ = + = eng J J 233 100 333 . (d) Q h , . net J J 333 250 83 3 W net J J 233 150 83 3 . Q c ,net = 0 The output of 83.3 J of energy from the heat engine by work in a cyclic process without any exhaust by
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