Câu hỏi 23

Theo đề 

${I_{01}} = {I_{02}} \Rightarrow {Z_{RL}} = {Z_{RC}} \Rightarrow \left\{ \matrix{
{{\rm{\varphi }}_{\rm{1}}}{\rm{ = - }}{{\rm{\varphi }}_{\rm{2}}}\left( 1 \right) \hfill \cr
{Z_L} = {Z_C} \hfill \cr} \right.$

Mặt khác 

$\left. \matrix{
{{\rm{\varphi }}_{\rm{u}}}{\rm{ - }}{{\rm{\varphi }}_{{i_1}}}{\rm{ = }}{{\rm{\varphi }}_{\rm{1}}}\left( 2 \right) \hfill \cr
{{\rm{\varphi }}_{\rm{u}}}{\rm{ - }}{{\rm{\varphi }}_{{i_2}}}{\rm{ = }}{{\rm{\varphi }}_{\rm{2}}} \hfill \cr} \right\}\mathop \Rightarrow \limits^{\left( 1 \right)} {{\rm{\varphi }}_{\rm{u}}} = {{{{\rm{\varphi }}_{{i_1}}} + {{\rm{\varphi }}_{{i_2}}}} \over 2} = {{\rm{\pi }} \over {\rm{4}}}\left( 3 \right)$

Từ $\left( 2 \right),\left( 3 \right) \Rightarrow {{\rm{\varphi }}_{\rm{1}}} = {{\rm{\pi }} \over {\rm{3}}} \Rightarrow {{{Z_L}} \over R} = \sqrt 3  \Rightarrow {Z_L} = 60\sqrt 3 \left( {\rm{\Omega }} \right)$

$ \Rightarrow {U_0} = {I_{01}}{Z_{RL}} = 120\sqrt 2 \left( V \right)$

Khi $RL{C_{}}nt \to $cộng hưởng: \(i = {{{U_0}} \over R}\cos \left( {100\pi t + {\varphi _u}} \right) = 2\sqrt 2 \cos \left( {100\pi t + {\pi  \over 4}} \right)\)