Đáp án:

 a.

$\begin{array}{l}
{I_1} = {I_3} = 1,17\left( A \right)\\
{I_2} = {I_4} = 0,78\left( A \right)
\end{array}$

b.${U_{AB}} = 7,02\left( V \right)$

c,

$\begin{array}{l}
{P_{nguon}} = 15,21\left( {\rm{w}} \right)\\
{P_{AB}} = 13,689\left( {\rm{w}} \right)
\end{array}$

Giải thích các bước giải:

$\begin{array}{l}
a.\left( {{R_1}nt{R_3}} \right)//\left( {{R_2}nt{R_4}} \right)\\
{R_{13}} = {R_1} + {R_3} = 6\\
{R_{24}} = {R_2} + {R_4} = 9\\
{R_{AB}} = \frac{{{R_{13}}{R_{24}}}}{{{R_{13}} + {R_{24}}}} = 3,6\\
I = \frac{\xi }{{r + {R_{AB}}}} = \frac{{7,8}}{{0,4 + 3,6}} = 1,95\\
{U_{AB}} = {U_{13}} = {U_{24}} = I.{R_{AB}} = 7,02\\
{I_{13}} = {I_1} = {I_3} = \frac{{{U_{13}}}}{{{R_{13}}}} = \frac{{7,02}}{6} = 1,17\left( A \right)\\
{I_{24}} = {I_2} = {I_4} = \frac{{{U_{24}}}}{{{R_{24}}}} = \frac{{7,02}}{9} = 0,78\left( A \right)\\
b,{U_{AB}} = 7,02\left( V \right)\\
c.{P_{nguon}} = \xi I = 7,8.1,95 = 15,21\left( {\rm{w}} \right)\\
{P_{AB}} = {U_{AB}}I = 7,02.1,95 = 13,689\left( {\rm{w}} \right)
\end{array}$