I live in a faraway village. There is no wireless network or telephone signals. I am a farmer. I work hard, but I only get 2000 dollars a year. If I want to contact my friends in Shanghai, I will ________ .
【简答题】单回路电路(串联电路)如图1.29所示,已知Us1 =15 V,Us2 = 5 V,R1 = 1Ω,R2 = 3Ω,R3 = 4Ω,R4 = 2Ω,求回路电流I和电压Uab。 单回路电路(串联电路)如图 1.29 所示,已知 U s1 =15 V , U s2 = 5 V , R 1 = 1Ω , R 2 = 3Ω , R 3 = 4Ω , R 4 = 2Ω ,求回路电流 I 和电压 U ab 。