If two AC generators are to be operated in parallel, the load is distributed evenly by（）

单项选择题If a voltmeter is connected across a line, it must be protected with a（）

A.shunt
B.high-resistance coil in the armature circuit
C.low-resistance coil in the armature circuit
D.shunt and a coil of high resistance

单项选择题When current and voltage reach maximum values at the same time, the power factor is（）

A.minimum
B.maximum
C.leading
D.lagging

单项选择题Which is an acceptable means of correcting high mica between commutator bars?（）

单项选择题Generator brushes are staggered to（）

A.reduce current pulsations
B.reduce brush chatter
C.prevent uneven commutator wear
D.allow greater power generation

单项选择题The voltage output of an AC generator is controlled by（）

A.varying the DC exciter voltage
B.varying the reluctance of the air gap
C.regulating the speed of the prime mover
D.shorting out part of the armature windings