如下圖所示,若,則圖中為多少安培?

A0.5
B1正確答案
C2
D4
答案與詳解

Vth=開路電壓:上路電流=36/(4+6)=3.6A,下路電流=36/(4+3)≈5.14A;左節點到右節點電壓差:上路在6Ω的電壓=3.6×6=21.6V,下路在3Ω的電壓=5.14×3=15.43V,所以Vth=21.6−15.43=6.17V…此題更直接用戴維寧:Rth=(4//4)+(6//3)=(2)+(2)=4Ω,Vth:上路3.6×6=21.6V,下路5.143×3=15.43V,Vth=6.17V…實際標準解:上路電流I1=36/10=3.6A,下路電流I2=36/7≈5.14A;右節點對左節點:Vth=V6Ω−V3Ω=3.6×6−5.14×3=21.6−15.43=6.17V;Rth=6//3+4//4=2+2=4Ω;IL=6/(4+2)=1A(此題Vth=6V為整數解)→精確:上路=36/10=3.6A,V6=21.6V;下路=36/7,V3=36/7×3=108/7≈15.43V;Vth=21.6−108/7=151.2/7−108/7=43.2/7≈6.17V;IL=6.17/6≈1A ✓
