单项选择题
A.Alternators B.Wave guides C.Exciters D.Amplidynes
If the length of a wire is halved and the cross-section...
单项选择题If the length of a wire is halved and the cross-sectional area is doubled, the resistance will be （）
A.quartered B.unchanged C.doubled D.quadrupled
AC and DC generators are similar in that they （）A.both ...
单项选择题AC and DC generators are similar in that they （）
A.both generate alternating voltages B.both rectify the voltage before delivery C.are constructed at the same physical size for the same kilowatt rating D.both supply three-phase power
To increase the frequency of an operating AC generator,...
单项选择题To increase the frequency of an operating AC generator, you should （）
A.increase the field excitation B.decrease the field excitation C.increase the number of magnetic poles D.increase the speed of the prime mover
