Đáp án:
${R_2} = 3,6\left( \Omega \right)$
${R_3} = 2\left( \Omega \right)$
Giải thích các bước giải:
k mở:
$\begin{array}{l}
{I_1} = \frac{U}{{{R_1} + {R_3}}}\\
\Rightarrow 1,2 = \frac{6}{{3 + {R_3}}} \Rightarrow {R_3} = 2\left( \Omega \right)
\end{array}$
K đóng
$\begin{array}{l}
{R_1}nt\left( {{R_2}//{R_3}} \right)\\
{R_{23}} = \frac{{{R_2}{R_3}}}{{{R_2} + {R_3}}} = \frac{{2{R_2}}}{{2 + {R_2}}}\\
{R_{123}} = {R_1} + {R_{23}} = 3 + {R_{23}}\\
{I_2} = 0,5 \Rightarrow {U_2} = {U_{23}} = {I_2}.{R_2} = 0,5{R_2}\\
I = \frac{{{U_{23}}}}{{{R_{23}}}} = \frac{{0,5{R_2}}}{{{R_{23}}}}\\
U = I.{R_{123}} = \frac{{0,5{R_2}}}{{{R_{23}}}}.\left( {3 + {R_{23}}} \right)\\
\Rightarrow 6 = \frac{{1,5{R_2}}}{{{R_{23}}}} + 0,5{R_2}\\
\Rightarrow 6 = \frac{{1,5{R_2}}}{{\frac{{2{R_2}}}{{2 + {R_2}}}}} + 0,5{R_2}
\end{array}$
$ \Rightarrow {R_2} = 3,6\left( \Omega \right)$
