Question

Find the currents $I_1$ and $I_2$ for the circuit shown in given figure.

• A. $I_1=-6A$ and $I_2=9A$
• B. $I_1=6A$ and $I_2=9A$
• C. $I_1=-6A$ and $I_2=-9A$
• D. $I_1=-9A$ and $I_2=6A$

Answer 1

The correct option is A $I_1=-6A$ and $I_2=9A$

Consider node $a$, using Kirchhoff's current law

(using $+$ for $I_{in}$ $-$ for $I_{out}$)

$\sum I_{atanode}=0$

$-3+2+I_{ab}=0$

$I_{ab}=1A$

Consider node $b$,

$I_{ba}+7+I_1=0$ ($I_{ab}=-I_{ba}$)

$-1-7+I_1=0$

$I_1=-6A$

Consider node $d$ ,

$I_{dc}+4-1=0$

$I_{dc}=-3A$

Consider node $c$,

$-I_2+6+I_{cd}=0$

$-I_2+6+3=0$

$I_2=9A$

$optionAiscorrect$