Question

（戴维南定理）US1=30V,R1=20,R2=10,US2=18V,R3=5,R4=10,R=10,试用戴维南定理求R两端的电压

Answer 1

R1 * (I1+I2) + R2 * I1 = Us1

R1 * (I1+I2) + (R+R3) * I2 = （Us1 - Us2）

解得：

I1 = 0.754 A

I2 = - 0.369 A

Uab = R3 * I2 + Us2

       = 16.155 V

Rab = (R + R1 // R2) // R3

       = 3.846 Ω

I = Uab / (Rab + R4)

  = 16.155 / 13.846

 = 1.167 A

追问

额，不是求电流....

追答

Va = 30 * 10 / (10+20) = 10 V

Vb = 18 * 10 / (10+5) = 12 V

Uab = Va - Vb = - 2 V

Rab = 20 // 10 + 5 // 10 = 10 Ω

Iab = Uab / (Rab + R) = - 2 / 20 = - 0.1 A

 UR = Iab * R = - 0.1 * 10 = - 1 V