單項(xiàng)選擇題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


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1.單項(xiàng)選擇題When current and voltage reach maximum values at the same time, the power factor is()

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

2.單項(xiàng)選擇題Which is an acceptable means of correcting high mica between commutator bars?()

A.undercutting
B.sanding
C.burnishing
D.filing

3.單項(xiàng)選擇題Generator brushes are staggered to()

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

4.單項(xiàng)選擇題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

5.單項(xiàng)選擇題If two AC generators are operated in parallel, the load is distributed evenly by()

A.a rheostat
B.a balancing coil
C.changing field excitation
D.adjusting the governor settings