I = 32 / (1 + 15) = 2 A
Uab = 8 * 2 - 10 = 6 V
Rab = 8 // 8 + 2 = 6 Ω
http://wenku.baidu.com/view/1a26938d8762caaedd33d4bc.html
开路电压Uab=16V-10V=6V，等效内阻：把电压源看成导线，Rab=8//8+2=6Ω
