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单选题
If a small electric motor is immersed in salt water it should be （） (1) washed in fresh water (2) dried in an oven
A
(1) only
B
(2) only
C
both (1) and (2)
D
neither (1) or (2)
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更多 “单选题If a small electric motor is immersed in salt water it should be （） (1) washed in fresh water (2) dried in an ovenA (1) onlyB (2) onlyC both (1) and (2)D neither (1) or (2)” 相关考题
考题
The word "immersed" in the second paragraph means“______”.A. liftedB. raisedC. roseD. under water
考题
In an AC.synchronous motor electric propulsion plant,propeller speed is controlled by()
A.prime mover speedB.number of energized main motor polesC.propulsion generator field strengthD.electric coupling field strength
考题
The water in an auxiliary boiler should be tested for chloride content to determine ( ).A.total dissolved solidsB.salt contaminationC.water harcnessD.chlorine contamination
考题
请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.
It can be known from the passage that increase in the salinity of ocean water is caused by__________.
查看材料A．melting of sea ice
B．precipitation
C．evaporation
D．supplement of salt
考题
共用题干
Where Has the Salt Come from?Every now and then,we meet a fact about our earth that makes us feel strange and no answer for the fact has yet been found.Such a fact is the existence of salt in the oceans. How did it get there?We simply do not know how the salt got into the ocean!We do know,of course,that salt is water-soluble,and so passes into the oceans with rainwater.The salt of the earth's surface is constantly being dissolved（溶解）and is passing into the ocean.But we do not know whether this can explain the huge quantity of salt in oceans.If all the oceans were dried up,enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator（赤道）!The common salt that we all use is produced from seawater or the water of salt lakes, from salt springs（源泉）and from deposits of rock salt. The concentration（浓度）of salt in seawater ranges from about three percent to three-and-one-half percent. The Dead Sea, which covers an area of about 340 square miles,contains about 11,600,000,000 tons of salt!On the average, a gallon（加仑）of seawater contains about a quarter of a pound of salt.The beds of rock salt that are found in various parts of the world were all originally formed by the evaporation（蒸发）of seawater millions of years ago. It is believed that the thick rock-salt deposits were formed after about nine-tenth of theY volume of seawater had been evaporated.Most commercial salt is obtained from rock salt.The usual method is to drill wells（井） down to the salt beds. Pure water is pumped down（抽进去）through a pipe. The water dissolves the salt and it is forced through another pipe up to the surface.A:Right B:Wrong C:Not mentioned
考题
共用题干
Where Has the Salt Come from?Every now and then,we meet a fact about our earth that makes us feel strange and no answer for the fact has yet been found.Such a fact is the existence of salt in the oceans. How did it get there?We simply do not know how the salt got into the ocean!We do know,of course,that salt is water-soluble,and so passes into the oceans with rainwater.The salt of the earth's surface is constantly being dissolved（溶解）and is passing into the ocean.But we do not know whether this can explain the huge quantity of salt in oceans.If all the oceans were dried up,enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator（赤道）!The common salt that we all use is produced from seawater or the water of salt lakes, from salt springs（源泉）and from deposits of rock salt. The concentration（浓度）of salt in seawater ranges from about three percent to three-and-one-half percent. The Dead Sea, which covers an area of about 340 square miles,contains about 11,600,000,000 tons of salt!On the average, a gallon（加仑）of seawater contains about a quarter of a pound of salt.The beds of rock salt that are found in various parts of the world were all originally formed by the evaporation（蒸发）of seawater millions of years ago. It is believed that the thick rock-salt deposits were formed after about nine-tenth of theY volume of seawater had been evaporated.Most commercial salt is obtained from rock salt.The usual method is to drill wells（井） down to the salt beds. Pure water is pumped down（抽进去）through a pipe. The water dissolves the salt and it is forced through another pipe up to the surface.Beds of rock salt are found in every part of the world.A:Right B:Wrong C:Not mentioned
考题
共用题干
Where Has the Salt Come from?Every now and then,we meet a fact about our earth that makes us feel strange and no answer for the fact has yet been found.Such a fact is the existence of salt in the oceans. How did it get there?We simply do not know how the salt got into the ocean!We do know,of course,that salt is water-soluble,and so passes into the oceans with rainwater.The salt of the earth's surface is constantly being dissolved（溶解）and is passing into the ocean.But we do not know whether this can explain the huge quantity of salt in oceans.If all the oceans were dried up,enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator（赤道）!The common salt that we all use is produced from seawater or the water of salt lakes, from salt springs（源泉）and from deposits of rock salt. The concentration（浓度）of salt in seawater ranges from about three percent to three-and-one-half percent. The Dead Sea, which covers an area of about 340 square miles,contains about 11,600,000,000 tons of salt!On the average, a gallon（加仑）of seawater contains about a quarter of a pound of salt.The beds of rock salt that are found in various parts of the world were all originally formed by the evaporation（蒸发）of seawater millions of years ago. It is believed that the thick rock-salt deposits were formed after about nine-tenth of theY volume of seawater had been evaporated.Most commercial salt is obtained from rock salt.The usual method is to drill wells（井） down to the salt beds. Pure water is pumped down（抽进去）through a pipe. The water dissolves the salt and it is forced through another pipe up to the surface.The author is sure that the dissolved salt from the earth's surface is the only source of the huge quantity of salt found in oceans.A:Right B:Wrong C:Not mentioned
考题
单选题Passage2 Questions 6 to 10 are based on the following passage. Salt is as necessary to life as water. In many areas of Africa people once drank the urine（尿）of animals because they had no other source of salt. Without salt, human beings die. The human body demands that the amount of salt in the blood always stay the same. When the body does not get enough salt, it protects itself by letting less salt leave the body in. urine and sweat. But it cannot reduce this output to zero. Some salt is always escaping. On a completely saltless diet, like that of some people in Africa, the body steadily loses small amounts of salt through the kidneys（肾） and sweat glands(腺). It then tries to adjust to this loss by speeding up its secretion(分泌) of water. (78) In this way, the body attempts to keep the amount of salt in the blood at the necessary level. The result is a slow drying up of body and, finally, death. The person dies of thirst. In cases where there is little or no water to drink, the body tries to do the opposite thing.Again, it must keep the salt level in the blood constant. Because it has little water, it attempts to stop water from leaving the body and to increase its secretion of. salt. But, as with the escaping salt, it cannot be completely successful. Some water still leaves and the person eventually dies of thirst. In short, the body's normal needs for salt and for water are both parts of the same important need to keep the salt level in the blood constant.6 Some African people once drank animal urine______.A
when they were going to dieB
because they were thirstyC
because there was little saltD
because they were short of water
考题
单选题The motor for the fresh water pump （）.A
need to repairB
need to be repairedC
needs to repairD
needs repairing
考题
单选题操作完后，关掉电动机。（）A
After operation, start the electric motor.B
Before operation, stop the electric motor.C
Before operation, start the electric motor.D
After operation, stop the electric motor.
考题
单选题You are transferring fuel from the storage tanks to the day tanks by means of an electric fuel oil transfer pumpIf the pump motor catches fire, you would FIRST （）.A
secure the fuel manifoldB
shut off power to the pumpC
shut off the power ventilationD
spray water on the fire
考题
单选题Passage2 Questions 6 to 10 are based on the following passage. Salt is as necessary to life as water. In many areas of Africa people once drank the urine（尿）of animals because they had no other source of salt. Without salt, human beings die. The human body demands that the amount of salt in the blood always stay the same. When the body does not get enough salt, it protects itself by letting less salt leave the body in. urine and sweat. But it cannot reduce this output to zero. Some salt is always escaping. On a completely saltless diet, like that of some people in Africa, the body steadily loses small amounts of salt through the kidneys（肾） and sweat glands(腺). It then tries to adjust to this loss by speeding up its secretion(分泌) of water. (78) In this way, the body attempts to keep the amount of salt in the blood at the necessary level. The result is a slow drying up of body and, finally, death. The person dies of thirst. In cases where there is little or no water to drink, the body tries to do the opposite thing.Again, it must keep the salt level in the blood constant. Because it has little water, it attempts to stop water from leaving the body and to increase its secretion of. salt. But, as with the escaping salt, it cannot be completely successful. Some water still leaves and the person eventually dies of thirst. In short, the body's normal needs for salt and for water are both parts of the same important need to keep the salt level in the blood constant.10 What is the main idea of the passage?A
Salt is very important.B
If their blood salt level is not constant, human beings may die.C
The amount of salt in the body is secreted.D
People can die of thirst.
考题
单选题The primary function of an electric motor is to （）A
develop torqueB
generate high voltagesC
produce a magnetic fieldD
generate high electrical resistance
考题
单选题If the electric motor driving an air compressor fails to start, the cause may be a （）.A
leaking unloaderB
tripped circuit breakerC
control line leakD
defective pop valve
考题
单选题Any electric motor can be constructed to be（）.A
short proofB
ground proofC
explosion proofD
overload proof
考题
单选题“A centrifuge consists of an electric motor driving a vertical shaft on the top of which is mounted the bowl assembly”.According to this sentence, we can know that is mounted on the top of the vertical shaft（）A
a centrifugeB
an electric motorC
a bowl assemblyD
a driving motor
考题
单选题A salinity indicator is used to determine the （）.A
cause of salt contaminationB
location of salt water contaminationC
chemical makeup of feed-waterD
level of alkalinity in condensate
考题
单选题When there is a fire in a large electric motor, normally the very FIRST step is to （）A
secure the electric supplyB
ventilate area to remove smokeC
start the fire pump and lead out hoseD
apply foam
考题
单选题Passage2 Questions 6 to 10 are based on the following passage. Salt is as necessary to life as water. In many areas of Africa people once drank the urine（尿）of animals because they had no other source of salt. Without salt, human beings die. The human body demands that the amount of salt in the blood always stay the same. When the body does not get enough salt, it protects itself by letting less salt leave the body in. urine and sweat. But it cannot reduce this output to zero. Some salt is always escaping. On a completely saltless diet, like that of some people in Africa, the body steadily loses small amounts of salt through the kidneys（肾） and sweat glands(腺). It then tries to adjust to this loss by speeding up its secretion(分泌) of water. (78) In this way, the body attempts to keep the amount of salt in the blood at the necessary level. The result is a slow drying up of body and, finally, death. The person dies of thirst. In cases where there is little or no water to drink, the body tries to do the opposite thing.Again, it must keep the salt level in the blood constant. Because it has little water, it attempts to stop water from leaving the body and to increase its secretion of. salt. But, as with the escaping salt, it cannot be completely successful. Some water still leaves and the person eventually dies of thirst. In short, the body's normal needs for salt and for water are both parts of the same important need to keep the salt level in the blood constant.7 In order to adjust to the loss of salt, the body______.A
loses some bloodB
speeds up its secretion of waterC
speeds up its secretion of saltD
is drying up slowly
考题
单选题After operation, drop the control levers into stowing hole, and （）the electric motor.A
startB
stopC
moveD
open
考题
单选题To repair a small electrical motor that has been submerged in saltwater, you should （）.A
wash it with fresh water and apply an external source of heatB
renew the windingsC
send it ashore to an approved service facilityD
rinse all electrical parts with a carbon tetrachloride cleaning solvent and then blow dry the motor with compressed air
考题
单选题In motorships，there are two main circuits, （）.A
one salt water, one fresh waterB
one salt water, one fuelC
one fresh water, one fuelD
one steam, one fuel
考题
单选题After operation, drop the control levers into stowing hole, and （）(停止)the electric motor.A
startB
stopC
moveD
shift
考题
单选题What type of electric motor is most commonly used on board ship?（）A
non-synchronous electric motorB
synchronous electric motorC
fully enclosed electric motorD
watertight electric motor
考题
单选题（）provides strength and strong space for fule,lubricating oil,fresh water,salt(ballast)water and potable water.A
The double bottomB
The cofferdamC
The navigating bridgeD
The superstructure
考题
单选题Passage2 Questions 6 to 10 are based on the following passage. Salt is as necessary to life as water. In many areas of Africa people once drank the urine（尿）of animals because they had no other source of salt. Without salt, human beings die. The human body demands that the amount of salt in the blood always stay the same. When the body does not get enough salt, it protects itself by letting less salt leave the body in. urine and sweat. But it cannot reduce this output to zero. Some salt is always escaping. On a completely saltless diet, like that of some people in Africa, the body steadily loses small amounts of salt through the kidneys（肾） and sweat glands(腺). It then tries to adjust to this loss by speeding up its secretion(分泌) of water. (78) In this way, the body attempts to keep the amount of salt in the blood at the necessary level. The result is a slow drying up of body and, finally, death. The person dies of thirst. In cases where there is little or no water to drink, the body tries to do the opposite thing.Again, it must keep the salt level in the blood constant. Because it has little water, it attempts to stop water from leaving the body and to increase its secretion of. salt. But, as with the escaping salt, it cannot be completely successful. Some water still leaves and the person eventually dies of thirst. In short, the body's normal needs for salt and for water are both parts of the same important need to keep the salt level in the blood constant.8 Which of the following statements is NOT the result of a lack of salt in the body?A
The body secretes more water.B
The body dries up.C
The person dies of thirst.D
The person gets fatter.
考题
单选题Aluminum lifeboats are subject to damage by electrolytic corrosion (the aluminum being eaten away). In working around boats of aluminum you must be very careful（）.A
to keep the boats covered at all timesB
not to leave steel or iron tools lying in or near these boatsC
to keep an electric charge on the hull at all timesD
to rinse these boats regularly with salt water
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