如图,根据 KVL 绕行一圈:
Us - (is + u /2) * R1 - u - 2u = 0
u = 2/3 V
Uab = 2u = 4/3 V
a、b 端口是受控电压源,不能短路求电流,用外加电源法求网络内阻:
2 * u = 5 * I1 (1)
I1 = - u / 2 (2)
由(2)代入(1)得:
2 * u = 5 *(- u / 2)
u = 0
R0 = Uab / Is
= 2 * u / Is
= 0
等效电路:
受控源只是输出参数受激励源控制的理想电源.本题受控电压源与网络端口并联,可以直接得出内阻为零,