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Câu hỏi: Đặt điện áp $u={{U}_{0}}\cos \omega t\left( \text{V} \right)$ vào hai đầu cuộn cảm thuần có độ tự cảm L thì cường độ dòng điện qua cuộn cảm là
A. $i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t+\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
B. $i=\dfrac{{{U}_{0}}}{\omega L\sqrt{2}}\cos \left( \omega t+\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
C. $i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
D. $i=\dfrac{{{U}_{0}}}{\omega L\sqrt{2}}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
A. $i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t+\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
B. $i=\dfrac{{{U}_{0}}}{\omega L\sqrt{2}}\cos \left( \omega t+\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
C. $i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
D. $i=\dfrac{{{U}_{0}}}{\omega L\sqrt{2}}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
Có ${{I}_{0}}=\dfrac{{{U}_{0}}}{{{Z}_{L}}}=\dfrac{{{U}_{0}}}{\omega L};{{\varphi }_{{}^{{{u}_{L}}}/{}_{i}}}=\dfrac{\pi }{2}\Rightarrow {{\varphi }_{i}}={{\varphi }_{{{u}_{L}}}}-\dfrac{\pi }{2}=-\dfrac{\pi }{2}\left( \text{rad} \right)$
$\Rightarrow i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
$\Rightarrow i=\dfrac{{{U}_{0}}}{\omega L}\cos \left( \omega t-\dfrac{\pi }{2} \right)\left( \text{A} \right)$.
Đáp án C.