Read Text C and then finish the exercises.a. they invented it b. they practice it a lot c. they do it bettera. a sight of breathtaking beauty __________b. an outstanding achievement __________c. an act of abominable cruelty __________d. an unforgivably stupid misjudgement __________5) Why do most foreigners find the English understatement hard to get?
实验测得某有源二端线性网络的开路电压为10V。当外接3Ω电阻时,其端电压为6V,则该网络的等效电压源的参数为()。
A. US=6V,R0=3Ω
B. US=8V,R0=3Ω
C. US=10V,R0=2Ω
交流电的三要素是指最大值,角频率,( )。
A. 相位
B. 角度
C. 初相位
D. 电压
某正弦电压有效值为380V,频率为50Hz,在t=0时的值u(0)=380V,该正弦电压的表达式为( )
A. u=380sin314tV
B. u=537sin(314t+450)V
C. u=380sin(314t+900)V