homework_21.1_sol - Homework#3 Solution 12.5 q I JV J D2 Ix...

Unformatted text preview: Homework #3 Solution 12.5 q I JV J D2 Ix J J J J AJ 2 At A x 4 JJ V 3 4Ix 42 10 A2 10000m J D2 2 J 2 1.09762 102 3 m 2 2 C2 2 JJJ V 2 2 2 2 5.82 107 2 2 2J 2s 2m 22 200V 2 2 2 2 J electron J 2 J D J 3.31cm The required wire diameter is about 3.31 cm. 12.6 J diffusion J M JC J J At x 2 J J M JD 2 C J J J t 4x 1.772 102 9 m2 kg 2 2 2 1m 2 2 2 0.00042 2 02 3 s m 2 5.842 102 11 kg 42 0.01m s The rate at which carbon dioxide diffuse to the algae is kg 5.842 102 11 s 2 12.7 (a) Series: R S = R1 + R 2 = 5 + 10 = 15 (b) Parellel: 1 1 10 RP = = = 3.33 1 1 1 1 3 + + R1 R 2 5 10 12.8 R equiv = 12.13 1 1 1 + R1 R 2 + R3 = 1 1 1 + 20 10 + 5 = 20 35 + 5 = 11.67 3 3 . Let assume the heat resistance of each panel is the same, and denoted as R. Case I: uniformly covered with three layers R panel = 3R, J heat = 1000TApanel T T = , Qheat ,total ,1 = 1000 Apanel J heat = R panel 3R 3R Case II: half covered with four layers and half two layers R panel ,a = 2 R, J heat , a = R panel ,b = 4 R, J heat ,b = T R panel ,a T R panel ,b = = 250TApanel T , Qheat ,total , a = 500 Apanel J heat , a = 2R R 125TApanel T , Qheat ,total ,b = 500 Apanel J heat ,b = 4R R 375TApanel R Because 1000/3 < 375, so the first case, i.e., uniformly covering, will result in less energy consumption. Qheat ,total ,2 = Qheat ,total ,a + Qheat ,total ,b = ...
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