谐波导致损耗增加和设备寿命缩短。()倍次谐波即使在负载平衡的情况下也会使中线带电流,并且此电流有可能等于甚至大于相电流。
A.3
B.5
C.7
D.8
参考答案:A
密度为ρ=0.5×103kg/m3的小木球,从离水面高h=5m处由静止开始自由下落,然后落入足够深的水池中,如图5-3-19所示,若不计空气阻力和水的黏滞阻力,球在与水面撞击时无机械能损失.求:小木球在水中能下沉多深?
There a panda and two lions in yesterday’s film.
A. were B. was C. had