increases by the square of the original value
increases
remains the same
decreases
第1题：
ENCRYPT_TS is an encrypted tablespace that contains tables with data. Which statement is true regarding the effect of queries and data manipulation language (DML) statements on the encrypted data in the tables?（）
A. The data is decrypted during SORT and JOIN operations.
B. The data remains encrypted when it is read into memory.
C. The data remains encrypted when it is stored in the redo logs.
D. The data remains encrypted in the UNDO tablespace provided that the UNDO tablespace was created with the encryption option enabled.
第2题：
In the Northern Hemisphere a wind is said to veer when the wind ______.
A.changes direction clockwise, as from north to east, etc
B.changes direction counterclockwise, as from south to east, etc
C.changes direction violently and erratically
D.remains constant in direction and speed
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：
(1) only
(2) only
either (1) or (2)
neither (1) or (2)
第5题：
When replacing a power supply， what MUST the technician observe？（）
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：
According to Ohm’s Law， which of the following is correct？（）
第8题：
A.voltage step-up
B.current step-down
C.current step-up
D.resistance
第9题：
As long as
As far as
As well as
Unless
第10题：
Low voltage protection circuit
Non-renewable link fuse
Renewable link fuse
Low voltage release circuit