802_Physics ProblemsTechnical Physics

802_Physics ProblemsTechnical Physics - 142 P28.27 Direct...

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142 Direct Current Circuits P28.27 Using Kirchhoff’s rules, 12 0 0 010 0 0 060 0 0 10 0 1 00 0 060 0 13 23 .. . . −−= +− = bg afa f II 0 and III 123 =+ 12 0 0 010 0 070 0 10 0 1 00 0 060 0 0 . . = 0 0 af FIG. P28.27 Solving simultaneously, I 2 0283 = . A downward in the dead battery and I 3 171 = A downward in the starter. The currents are forward in the live battery and in the starter, relative to normal starting operation. The current is backward in the dead battery, tending to charge it up. P28.28 VII I VI I I I I ab ab ab =++− + =− + 100 500 300 11 2 12 1 2 2 ... afaf a f a f a f a f a f Let I = . A , Ix 1 = , and Iy 2 = . Then, the three equations become: Vx y ab 200 . , or yx V ab . y ab + + 400 600 and y ab + 800 800 . . Substituting the first into the last two gives: 700 800 . ab and 6 00 2 00 8 00 . ab . Solving these simultaneously yields V ab = 27 17 V. Then,
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