Đặt vào hai đầu đoạn mạch RLC mắc nối tiếp một đi...

C

- Hướng dẫn giải

Đáp án C

\(\begin{array}{l}{U_C} = \frac{{U{Z_C}}}{{\sqrt {{R^2} + {{\left( {{Z_{{L_1}}} - {Z_C}} \right)}^2}} }} = \frac{{U{Z_C}}}{{\sqrt {{R^2} + {{\left( {{Z_{{L_2}}} - {Z_C}} \right)}^2}} }}\\ \Rightarrow {Z_C} = \frac{{{Z_{{L_1}}} + {Z_{{L_2}}}}}{2} = \frac{{\omega \left( {{L_1} + {L_2}} \right)}}{2} = \omega .0,4\\{U_L} = \frac{{U{Z_L}}}{{\sqrt {{R^2} + {{\left( {{Z_L} - {Z_C}} \right)}^2}} }}\end{array}\)

L tới vô cùng  \({U_L} \approx U = {U_1}\) .

\(\begin{array}{l}{U_{{L_3}}} = {U_{{L_4}}} = \frac{{U{Z_{{L_3}}}}}{{\sqrt {{R^2} + {{\left( {{Z_{{L_3}}} - {Z_C}} \right)}^2}} }} = \frac{{U{Z_{{L_4}}}}}{{\sqrt {{R^2} + {{\left( {{Z_{{L_4}}} - {Z_C}} \right)}^2}} }} = 1,5U\\ \Rightarrow 1,{5^2}\left[ {{R^2} + {{\left( {{Z_{{L_3}}} - {Z_C}} \right)}^2}} \right] - Z_{{L_3}}^2 = 1,{5^2}\left[ {{R^2} + {{\left( {{Z_{{L_4}}} - {Z_C}} \right)}^2}} \right] - Z_{{L_4}}^2 = 0\\ \Rightarrow {Z_{{L_3}}} + {Z_{{L_4}}} = \frac{{1,{5^2}.2.{Z_C}}}{{1,{5^2} - 1}}\\ \Rightarrow {L_3} + {L_4} = \frac{{1,{5^2}.2.0,4}}{{1,{5^2} - 1}} = 1,44\left( H \right)\end{array}\)