全波整流、滤波电路如图所示,如果输入信号ui=10sin(t+30°)V,则开关S闭合前,输出电压u为()V。
A.0
B.7.64
C.10
D.12
参考答案:C
We should have in ourselves and we will make it if we have a try. [ ]
A. success
B. confidence
C. progress
蒸馏塔中部出现阻塞,可造成()。
A.塔顶温度升高
B.塔底压力升高
C.塔底压力降低