lagging
leading
maximum
minimum
第1题：
A circuit breaker and a fuse have a basic similarity(类似) in that they both ______.
A.can be reset to energize the circuit
B.should open the circuit when overloaded
C.will burn out when an over current flow develops
D.should short the circuit when overloaded
第2题：
A switchboard for an AC electrical system requires the use of which of the following devices?
A.Frequency meter.
B.Ohmmeter.
C.Induction voltage regulator.
D.Current transformer governor.
第3题：
When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____.
A.lagging
B.leading
C.maximum
D.minimum
第4题：
To cut out generators when they are no longer required
To cut in additional generators automatically as required
To divide the KW load equally between generators operating in parallel
To divide reactive current between generators operating in parallel
第5题：
Low voltage protection circuit
Non-renewable link fuse
Renewable link fuse
Low voltage release circuit
第6题：
材料：
The field current supply in older machines comes from a lower voltage direct current generator or exciter on the same shaft as the alternator. Modern machines however are either statically excited or of the high-speed brush-less type. The exciter is required to operate to counter the effects of power factor for a given load. The power factor is a measure of the phase difference between voltage and current and is expressed as the cosine of the phase angle. With a purely resistance load the voltage and the current are in phase, giving a power factor of one. The power consumed is therefore the product of voltage and current. Inductive or capacitive loads, combined with resistance loads, produce lagging or leading power factors which have a value less than one.
The power consumed is therefore the product of current, voltage and power factor. The alternating current generator supplying a load has a voltage drop resulting from the load. When the load has a lagging power factor this voltage drop is considerable. Therefore the exciter, in maintaining the alternator voltage, must vary with load current and also the power factor. The speed change of the prime mover must also be taken into account.
问题： The word “machines” in the passage refers to _____.
A.the direct current generator
B.the alternating current generator
C.the exciter
D.the prime mover
Which of the following statements is true according to the passage ?
A.With a purely resistance load, the power factor is zero
B.Inductive loads combined with resistance loads produces leading power factors
C.Capacitive loads combined with resistance loads produces lagging power factors
D.With a purely resistance load, the phase angle is zero
When the load has a lagging power factor this voltage drop is considerable. This sentence means that _____.A.with a purely resistance load, the voltage drops too much
B.there is a considerable voltage drop in the capacitive load combined with resistance load
C.when the load is the capacitive load combined with resistance load, the voltage drops to zero
D.when the load is the inductive load combined with resistance load, the voltage drop is fairly large
The exciter must vary with: ① load current ② the power factor, ③ speed change of the prime mover.A.①
B.②
C.①②
D.①②③
请帮忙给出每个问题的正确答案和分析，谢谢！
第7题：
A circuit breaker and a fuse have a basic similarity in that they both______.
A.can be reset to energize the circuit
B.should open the circuit when overloaded
C.will burn out when an over current flow develops
D.should short the circuit when overloaded
第8题：
Equal power factors on paralleled AC generators are maintained by an automatic ________.
A.governor control switch
B.reverse power relay
C.reverse current relay
D.voltage regulator
第9题：
capacitive circuit
inductive circuit
magnetic circuit
resistive circuit
第10题：
half the resistance of the other resistor
a resistance equal to the other
at least ten times the resistance of the other
a partial short circuit