题目内容
（请给出正确答案）
已知某电路元件的电压u(t)=20sin(314t+30°)V，电流I(t)=5cos(314t+30°)A，这个元件是()。
A．电阻
B．电感
C。电容
D．电压源
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更多“已知某电路元件的电压u（t)=20sin（314t+30°)V，电流I（t)=5cos（314t+30°)A，这个元件是（)。 A．电阻 B”相关的问题
A、3∠-53.1°V
B、3∠53.1°V
C、3∠-36.9°V
D、3∠36.9° V
如图所示耦合电感，已知M=
H，i=50sin50t A ，则电压u为（ ）V。
A、2.5cos50t
B、-2.5cos50t
C、2.5sin50t
D、-2.5sin50t
(1)分析电路工作原理和各元件的作用。
(2)调整R2，使加到变容管上的反向偏置电压VQ为6V时，它所呈现的电容CjQ=20pF，试求振荡回路的电感量L2。
(3)试求最大频偏Δfm和调制灵敏度SF=Δf/VΩm。
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|
图示电路中，已知u=10cos(ωt+60º)V，R、L不变，二端网络吸收的有功功率为P。当ω增大时， P的变化情况是（ ）。
A、不能确定
B、减小
C、增大
D、不变
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