[Lí 9] Cần Gấp

N

naruto_evil

Ta quy ước chiều dòng điện chạy từ M đến N ta có:
$\Large I_1=I_2=I_{12}=\frac{U_{MN}}{R_{12}}=\frac{40}{5+15}=2A$
$\Rightarrow U_1=I_1.R_1=2.5=10V$
$\Rightarrow U_2=I_2.R_2=2.15=30V$

$\Large I_3=I_4=I_5=I_{345}=\frac{U_{AB}}{R_{345}}=\frac{40}{4+6+10}=2A$
$\Rightarrow U_3=I_3.R_3=2.4=8V$
$\Rightarrow U_4=I_4.R_4=2.6=12V$
$\Rightarrow U_5=I_5.R_5=2.10=20V$

☼$U_{AB}=U_{AM}+U_{MB}=-U_{MA}+U_{MB}=-U_1+U_3=-10+8=-2V$
☼$U_{AC}=U_{AN}+U_{NC}=U_{AN}-U_{CN}=30-20=10V$
 
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