【单选题】已知 u 1 =60sin(314t+90°)V , u 2 =80sin(314t)V ,则 u 1 - u 2 = ( )。
A.
u 1 - u 2 =20sin(314t)V
B.
u 1 - u 2 =-20sin(314t)V
C.
u 1 - u 2 =100sin(314t+143.1°)V
D.
u 1 - u 2 =-20sin(314t-143.1°)V
【单选题】已知u1=20sin sin (314t + )V ,u2=40sin (314t - )V ,则( )。
【简答题】名词复数练习题 一、填入所给名词的正确形式。 1. I have two (knife)______. 2. There are many (box)______here . 3. There are many(bus)______ on the road. 4. A few(boy) _____are drawing on the wall. 5. The(child)____are playi...
【简答题】习题11-11图示电路,已知u 1 =400+100sin(3×314t)-20sin(6×314t)V,求电压u 2 。
【判断题】奥斯特洛夫斯基:“批评,这是正常的血液循环,没有它就不免有停滞和生病的现象。”
【单选题】广告效果评价中,( )指所有消费者中看到了所投放广告的人群比例,是第一重要指标。
【简答题】已知一RLC串联电路的端口电压和电流为 u(t)=[100cos(314t)+50cos(942t-30°)]V i(t)=[10cos(314t)+1.755cos(942t+θ 3 )]A 试求: 电压u的有效值,i的有效值以及电路的有功功率为
【简答题】已知u=220sin( 314t + 20°) V , i=10sin( 314t - 30°) A, u (超前/滞后)i。
【单选题】已知 u 1 =60sin(314t+90°)V , u 2 =80sin(314t)V ,则 u 1 + u 2 = ( )。
A.
u 1 + u 2 =140sin(314t)V
B.
u 1 + u 2 =100sin(314t)V
C.
u 1 + u 2 =100sin(314t+36.9°)V
D.
u 1 + u 2 =140sin(314t-36.9°)V