Đáp án:
b.
\[\begin{array}{l}
U = 21,67\left( V \right)\\
{U_3} = 15\left( V \right)\\
{U_1} = {U_2} = 6,67\left( V \right)
\end{array}\]
c,
\[\begin{array}{l}
.{I_1} = 0,3335\left( A \right)\\
{I_2} = 0,17\left( A \right)\\
{I_3} = 0,5\left( A \right)\\
d.Q = 13000\left( J \right)
\end{array}\]
Giải thích các bước giải:
\[\begin{array}{l}
b.{R_3}nt\left( {{R_1}//{R_2}} \right)\\
{R_{12}} = \frac{{{R_1}{R_2}}}{{{R_1} + {R_2}}} = \frac{{20.40}}{{20 + 40}} = \frac{{40}}{3}\\
{R_{123}} = {R_{12}} + {R_3} = \frac{{40}}{3} + 30 = \frac{{130}}{3}\\
U = I.{R_{123}} = 0,5.\frac{{130}}{3} = 21,67\left( V \right)\\
I = {I_3} = {I_{12}}\\
{U_3} = {I_3}{R_3} = 0,5.30 = 15\left( V \right)\\
{U_{12}} = {U_1} = {U_2} = {I_{12}}{R_{12}} = 0,5.\frac{{40}}{3} = 6,67\left( V \right)\\
c.{I_1} = \frac{{{U_1}}}{{{R_1}}} = \frac{{6,67}}{{20}} = 0,3335\left( A \right)\\
{I_2} = \frac{{{U_2}}}{{{R_2}}} = \frac{{6,67}}{{40}} = 0,17\left( A \right)\\
d.Q = {I^2}{R_{123}}t = 0,{5^2}.\frac{{130}}{3}.20.60 = 13000\left( J \right)
\end{array}\]
