Đáp án:
$\left[ \begin{array}{l}
R = 80\left( \Omega \right)\\
R = 45\left( \Omega \right)
\end{array} \right.$
Giải thích các bước giải:
$\begin{array}{l}
{Z_L} = L\omega = \frac{{1,4}}{\pi }.100\pi = 140\\
{Z_C} = \frac{1}{{\omega C}} = \frac{1}{{100\pi .\frac{{{{10}^{ - 4}}}}{{2\pi }}}} = 200\\
P = \frac{{{U^2}}}{{{{\left( {{Z_L} - {Z_C}} \right)}^2} + R}^2}R\\
\Rightarrow 320 = \frac{{{{200}^2}}}{{{{\left( {140 - 200} \right)}^2} + {R^2}}}R\\
\Rightarrow \left[ \begin{array}{l}
R = 80\left( \Omega \right)\\
R = 45\left( \Omega \right)
\end{array} \right.
\end{array}$
