Lời giải:Ta có: \(\left\{ \begin{array}{*{35}{l}}
{{u}_{(t)}}={{U}_{0}}\cos \left( 100\pi t+\frac{\pi }{3} \right) \\
{{i}_{(t)}}={{I}_{0}}\cos \left( 100\pi t+\frac{\pi }{3}-\frac{\pi }{2} \right)={{I}_{0}}\cos \left( 100\pi t-\frac{\pi }{6} \right) \\
\end{array} \right.\)
\(\Rightarrow {{i}_{\left( t+\frac{T}{4} \right)}}={{I}_{0}}\cos \left( 100\pi \left( t+\frac{T}{4} \right)-\frac{\pi }{6} \right)={{I}_{0}}\cos \left( 100\pi t+\frac{\pi }{3} \right)\)
\(\Rightarrow \frac{{{u}_{(t)}}}{i\left( t+\frac{T}{4} \right)}=\frac{{{U}_{0}}}{{{I}_{0}}}={{Z}_{L}}=\omega L=100\pi \frac{1}{2\pi }=50\Omega \)
Chọn C.
