问个节点电压方程如图我给出的方程是(1/8+1/2.5+1/4)un1-1/2.5un2-1/4un3 = -7/4(1/2+1/2.5+1/15)un2 - 1/2.5un1-1/15un3 = 0(1/4+1/15)un3 - 1/4un1-1/15un2 = -1.4iaia = (un1-un2)/4解得的结果是un1 = -3.24un2 = -1.39un3 = -0.81ia = 0.46

Question

问个节点电压方程

如图



我给出的方程是

(1/8+1/2.5+1/4)un1-1/2.5un2-1/4un3 = -7/4
(1/2+1/2.5+1/15)un2 - 1/2.5un1-1/15un3 = 0
(1/4+1/15)un3 - 1/4un1-1/15un2 = -1.4ia
ia = (un1-un2)/4


解得的结果是
un1 = -3.24
un2 = -1.39
un3 = -0.81
ia = 0.46


跟标准答案不符啊  书上用回路电流法解得




我的方程错在哪

Answer 1

你的节点电压方程第四个错了!
这个ia = (un1-un2)/4错了,应该是：
ia = (un1-un3)/4