【单选题】关于功率因数, 下列说法不正确的是( )。
B.
一端口网络的功率因数角是端口电压与电流的相位差
C.
无源一端口网络的功率因数角是其 等效阻抗的阻抗角
D.
一端口网络的功率因数是端口电压与电流相位差的正弦值
【单选题】He made his final __________ last winter and__________ from then on.
B.
appearance; disappeared
C.
disappearance; appeared
【多选题】随着我国在科研方面的投入,在相关领域取得了可观的成果,下列属于我国成果的是: ( )
【简答题】Henry Adams was an 1. _______ (America)businessman. He had his own boat. One day when he was sailing out of the bay, he found himself 2. _______ (carry)out to sea by a strong wind. He did not know 3. ...
【单选题】功率因数主要是用来衡量对系统电源的利用率,其中关于功率因数角 的说法正确的是( )
【简答题】Henry Adams was an 1. _______ (America)businessman. He had his own boat. One day when he was sailing out of the bay, he found himself 2. _______ (carry)out to sea by a strong wind. He did not know 3. ...
【简答题】发育毒性作用表现主要哪几种?各自的作用特点是什么?
【单选题】It can be concluded from the passage that______.
A.
people think too much of their appearance
B.
there is not a sure way of losing weight as yet
C.
surgery is the fastest way of losing weight
D.
going on diet is a safe way of losing weight
【简答题】书面表达。 以My best friend为题,用所给信息,写一篇短文. 1. Who is your best friend? 2. general appearance 3.personalities and abilities 4. future plans 注意: 1)使用正确的时态. 2)短文必须包括所有要点. 3) 80词左右,可适当增补细节. My best friend _____...
【单选题】关于功率因数的计算,()是正确的。
A.
功率因数角等于有功功率除以无功功率的反正铉值
B.
功率因数角等于有功功率除以无功功率的反余弦值
C.
功率因数角等于有功功率除以无功功率的反正切值
D.
功率因数角等于有功功率除以无功功率的反余切值