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【单选题】
直接变换的结构,让本地振荡频率等于 () 使中频为零,也称为零中频结构A.
载波
B.
调制信号
C.
直流信号
D.
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举一反三
【简答题】 图 2 电路中,若列写回路电流方程,回路电流的参考方向如图所示,则回路 1 的电流 i1为 ( ) , 回路 2 的电流i2为 ( ) , 回路 3 的电流i3为 ( )。 图2
【简答题】Tobacco is the second major cause of death in the world. It is responsible for the death of one in ten s worldwide (about 5 million deaths each year). If current smoking patterns continue, it wil...
【单选题】What Is Death? People in the past did not question the difference between life and death. They could see that a person died when his heart stopped beating. People have learned, however, that the body ...
A.
was easy to tell
B.
did not exist
C.
lay in the brain
D.
was open to debate
【单选题】--Don’t you think that was a ______ night? --Yes, we were almost ______ to death by the shaking of the earth.
A.
frightened; frightened
B.
frightening; frightening
C.
frightening; frightened
D.
frightened; frightening
【单选题】如图所示电路中,假设绕行方向为逆时针方向,则可列回路电压方程为( )。
A.
I3R3-E2+I2R2-I1R1+E1=0
B.
I1R3-E2+I2R2+I1R1-E=0
C.
-I3R3+E1-I1R1+I2R2-E2=0
D.
-I3R3-E1+I1R1-I2R2+E2=0
【单选题】如图所示电路abda回路中,设定顺时针为绕行方向,则正确的KVL方程为( )
A.
I1R1+I3R3-V1=0
B.
R1+R3-V1=0
C.
I1R1+I3R3+V1=0
D.
I1R1-I3R3-V1=0
【单选题】What Is Death? People in the past did not question the difference between life and death. They could see that a person died when his heart stopped beating. People have learned, however, that the body ...
A.
did not exist.
B.
was easy to tell.
C.
lay in the brain.
D.
was open to debate.
【单选题】What Is Death? People in the past did not question the difference between life and death. They could see that a person died when his heart stopped beating. People have learned, however, that the body ...
A.
did not exist.
B.
was easy to tell.
C.
lay in the brain.
D.
was open to debate.
【单选题】在如图所示的电路中,假设绕行方向为逆时针方向,则可列出回路电压方程为( )
A.
I3R3 - E2 + I2R2 - I1R1 + E1 = 0
B.
I3R3 - E2 + I2R2 + I1R1 - E1 = 0
C.
-I3R3 + E1 - I1R1 + I2R2 + E2 = 0
D.
-I3R3 - E1 + I1R1 - I2R2 + E2 = 0
【单选题】如图所示电路中的bcdb回路中,以逆时针为绕行方向,正确的KVL方程为( )
A.
I2R2+I3R3+V2=0
B.
I2R2-I3R3+V2=0
C.
I2R2-I3R3-V2=0
D.
I2R2+I3R3=V2
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