the same as
much larger than
less than
equals
第1题：
In an operating diesel engine, which of the following conditions is an indication of a leaking air starting valve?
A.Noise coming from that air starting valve
B.Continuous operation of the starting air compressor
C.Zero air pressure in the air starting system
D.Overheated starting air pipe to the cylinder head
第2题：
If the Shipowner agrees to the voyage originally ordered by the Charterer，he is entitled to be paid hire ______ for the excess period．
A.at a higher rate decided by the owner
B.at a lower rate decided by the charterer
C.at a reasonable rate
D.at the current market rate
第3题：
Why did Sturgeon's electromagnet could support nine pounds of iron?
A. Because the iron rod was bent into the shape of a “horseshoe”.
B. Because the rod was coated with varnish.
C. Because a layer of copper wire was wrapped around the rod.
D. Because the rod was made magnetic by the passing current.
第4题：
第5题：
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：
If an attempt is made to hoist a load that exceeds the capacity of an electric winch，an overload safety device causes a circuit breaker to cut off the current to the winch motor ______．
A.when the line pull reaches the rated winch capacity
B.after the line pull exceeds the rated winch capacity
C.after a short build-up of torque
D.immediately
第8题：
A.much initial current
B.direct current
C.little initial current
D.constant current
第9题：
第10题：
额定转速（rated speed）