如右圖所示,電源電流I的值為何?

A9.12∠15.48°
B10.78∠16.67°
C11.55∠17.96°正確答案
D12.63∠18.16°
答案與詳解

支路1: Z1=3-j4Ω → I1=40/(3-j4)=40(3+j4)/25=4.8+j6.4A;支路2: Z2=5+j12Ω → I2=40/(5+j12)=40(5-j12)/169≈1.183-j2.840A;支路3: Z3=8Ω → I3=40/8=5+j0A;總I=(4.8+1.183+5)+j(6.4-2.840)=10.983+j3.56≈11.55∠17.96°
