Đặt điện á...

A

- Hướng dẫn giải

Ta có:

\(\begin{array}{l}{\omega ^2}LC = 3 \Rightarrow {Z_L} = 3{Z_C} \Rightarrow {u_C} = - \frac{{{u_L}}}{3}\\\left\{ \begin{array}{l}{u_{AN}} = {u_L} + {u_X}\\{u_{MB}} = {u_X} + {u_C}\end{array} \right. \Rightarrow {u_{AN}} - {u_{MB}} = {u_L} - {u_C} = {u_L} - \left( { - \frac{{{u_L}}}{3}} \right) = \frac{4}{3}{u_L}\\{u_X} = {u_{AN}} - {u_L} = \left( {60\sqrt 2 \angle 60} \right) - 45\sqrt 6 \angle 150 \approx 15\sqrt {86} \angle 7,6\\ \Rightarrow {U_{MN}} = {U_X} = \frac{{{U_{0X}}}}{{\sqrt 2 }} = \frac{{\left( {15\sqrt {86} } \right)}}{{\sqrt 2 }} \approx 98\end{array}\)