单项选择题
A.sine B.cosine C.tangent D.cotangent
With a purely resistance load the voltage and current a...
单项选择题With a purely resistance load the voltage and current are in phase, giving a power factor of （）.
A.one B.less than one C.more than one D.negative one
The alternating current generator supplying a load has ...
单项选择题The alternating current generator supplying a load has a voltage drop resulted from the loadWhen the load has a lagging power factor this voltage drop （）.
A.is small B.may be neglected C.is useful D.is considerable
After the trouble of the automatic control system has b...
单项选择题After the trouble of the automatic control system has been completely eliminated, assistance is （） required.
A.remained B.still C.no longer D.much mere
