单选题Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.Aincrease in resistance with increased temperatureBincrease in resistance with decreased temperatureCdecrease in resistance with increased temperatureDincrease in conductance with increased temperature
单选题
Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.
A
increase in resistance with increased temperature
B
increase in resistance with decreased temperature
C
decrease in resistance with increased temperature
D
increase in conductance with increased temperature
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Passage TwoQuestions 26 to 30 are based on the following passage.The electromagnet was invented in England by William Sturgeon，who took an iron rod and bent it into the shape of a horseshoe. This “horseshoe” was coated with varnish and a layer of copper wire was wrapped around it. An electric current was passed through the wire，thus making the rod magnetic. The rod was now，because of magnetic attraction，able to support nine pounds of iron. In the US，a scientist named Joseph Henry improved on Sturgeon's electromagnet by insulating the copper wine with silk. He was able to wrap many turns of wire around an iron core without danger of short circuits between the turns. His magnet could hold 2,300 pounds. This experiment prompted Henry to try his hand at converting magnetism into electricity. First he coiled some insulated wire around an iron bar. connecting both ends of the wire to a galvanometer(电流表). The iron bar was placed across the poles of the electromagnet. Then the coil of the electromagnet was connected to a battery. The galvanometer indicated a voltage，then dropped to zero. Henry signaled his assistant to disconnect the coil. The galvanometer showed that once again a voltage had been produced，although this time in the opposite direction. The principle of electromagnetic induction had thus been discovered. Unfortunately for Joseph Henry he did not publish his findings and someone else(Faraday)got the credit for the discovery.The principle of electromagnetic was discovered by______.A. William SturgeonB. Joseph HenryC. FaradayD. someone else
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.
When placed in a magnetic field, which of the materials listed will maintain the highest permeability?( )A.GlassB.BakeliteC.Soft ironD.Aluminum
You are carrying cargoes of crotonaldehyde，phosphoric acid，and morpholine on your multiple-product tanker. Which of the following statements is TRUE?A.Each of the cargoes must be segregated from the other by at least two barriersB.The minimum protective clothing required for taking samples of phosphoric acid is goggles or a face shieldC.Aluminum，copper，and zinc are prohibited in all valve parts in contact with these cargoesD.The required warning sign must have the legend "cancer hazard" added to it
You are on a multiple product tanker and carrying methyl acrylate，diethanolamine，and triethylamine. Which statement is TRUE?A.Methyl acrylate may be loaded in a tank adjacent to diethanolamine but not triethylamineB.The heating coils to the cargo tank loaded with methyl acrylate must be blanked offC.Valve components made of aluminum，copper，or zinc may not be in contact with the cargoesD.Each crew member working on deck must have an emergency escape breathing apparatus
Foam-type portable fire extinguishers are most useful in combating fires involving ______.A.solid materials such as wood or bales of fiberB.inflammable liquidsC.electrical equipmentD.metallic solids
共用题干第三篇Iron DeficienciesExperts have observed for years that endurance athletes,particularly females,frequently have iron deficiencies.Now a new study by a team of Purdue University researchers suggests that even moderate exercise may lead to reduced iron in the blood of women."We found that women who were normally inactive and then started a program of moderate exercise showed evidence of iron loss,"says Roseanne M.Lyle,associate professor at Purdue.Her study of 62 formerly inactive women who began exercising three times a week for six months was published in the journal Medicine & Science in Sports & Exercise."Women who consumed additional meat or took iron supplements were able to bounce back,"she notes."But the new exercisers who followed their normal diet showed a significant decrease in iron levels."Iron deficiency is very common among women in general,affecting one in four female teenagers and one in five women aged 18 to 45,respectively.But the ratio is even greater among active women,affecting up to 80 percent of female endurance athletes.This means,Lyle says,that"too many women ignore the amount of iron they take in."Women of childbearing age are at greatest risk,since their monthly bleeding is a major source of iron loss.Plus,many health-conscious women increase their risk by rejecting red meat,which contains the most easily absorbed form of iron.And because women often restrict their diet in an effort to control weight,they may not consume enough iron-rich food,and are liable to experience a deficiency."The average woman takes in only two thirds of the recommended daily allowance of iron," notes another expert."For a woman who already has a poor iron status,any additional iron loss from exercise may be enough to tip her over the edge into a more serious deficiency,"notes the expert. Exercise can result in iron loss through a variety of mechanisms.Some iron is lost in sweat,and,for unknown reasons,intense endurance exercise is sometimes associated with bleeding of the digestive system.The best sources of iron,and the only sources of the form of iron most readily absorbed by the body,are meat,chicken,and fish.Good sources of other forms of iron include dates,beans,and some leafy green vegetables.Who will have a significant decrease in iron levels?A:All the women.B:All the inactive women.C:Women who start to do moderate exercise and follow their normal diet.D:Women who start to do moderate exercise and consume additional meat or take iron supplements.
共用题干第三篇Iron DeficienciesExperts have observed for years that endurance athletes,particularly females,frequently have iron deficiencies.Now a new study by a team of Purdue University researchers suggests that even moderate exercise may lead to reduced iron in the blood of women."We found that women who were normally inactive and then started a program of moderate exercise showed evidence of iron loss,"says Roseanne M.Lyle,associate professor at Purdue.Her study of 62 formerly inactive women who began exercising three times a week for six months was published in the journal Medicine & Science in Sports & Exercise."Women who consumed additional meat or took iron supplements were able to bounce back,"she notes."But the new exercisers who followed their normal diet showed a significant decrease in iron levels."Iron deficiency is very common among women in general,affecting one in four female teenagers and one in five women aged 18 to 45,respectively.But the ratio is even greater among active women,affecting up to 80 percent of female endurance athletes.This means,Lyle says,that"too many women ignore the amount of iron they take in."Women of childbearing age are at greatest risk,since their monthly bleeding is a major source of iron loss.Plus,many health-conscious women increase their risk by rejecting red meat,which contains the most easily absorbed form of iron.And because women often restrict their diet in an effort to control weight,they may not consume enough iron-rich food,and are liable to experience a deficiency."The average woman takes in only two thirds of the recommended daily allowance of iron," notes another expert."For a woman who already has a poor iron status,any additional iron loss from exercise may be enough to tip her over the edge into a more serious deficiency,"notes the expert. Exercise can result in iron loss through a variety of mechanisms.Some iron is lost in sweat,and,for unknown reasons,intense endurance exercise is sometimes associated with bleeding of the digestive system.The best sources of iron,and the only sources of the form of iron most readily absorbed by the body,are meat,chicken,and fish.Good sources of other forms of iron include dates,beans,and some leafy green vegetables.Who will show evidence of iron loss?A:Inactive women.B:Active women.C:Women who do a program of moderate exercises regularly.D:Women who are inactive and start to do moderate exercises.
According to Paragraph 5，the EEOB’s decoration details( ) A.had almost no cast iron and plaster B.hardly use of wood for fireproofing C.are with the materials of granite，bronze，and glass D.are with carved wood，oriental rugs，and stenciled wall patterns
Exports are either raw materials or manufactured goods. Raw materials are products of the land， such as cotton， timber or rubber. Some raw materials， such as iron ore， come from mines. These raw materials are often exported by the countries that produce them to other countries where they are made into manufactured goods. Some countries produce food for export， for example， meat， sugar， or cereals such as wheat and maize. These countries are agricultural countries. An agricultural country needs fertile land and a good climate. A cold， dry climate is not suitable for agriculture. A country which produces manufactured goods is known as an industrialized country. An industrialized country cannot always produce enough food for its own needs. In this case， it does not export foodstuffs. Instead it has to import them. It relies on exports of manufactured products and pays for imports with the money it earns from the exported goods. Raw materials are often exported by the countries that produce them to other countries where（）.Athey are consumedBthey are made into finished productsCthey are wasted
Ireland is one of the leading exporters of（）in Europe.A、coal and iron oreB、silver and goldC、copper and aluminumD、lead and zinc
单选题An advantage of aluminum pistons, when compared to cast iron pistons is （）.Agreater high temperature strengthBbetter heat conductivityCgreater weight per cubic inchDincreased resistance to wear
单选题Foam-type portable fire extinguishers are most useful in combating fires involving（）.Asolid materials such as wood or bales of fiberBinflammable liquidsCelectrical equipmentDmetallic solids
单选题Cast irons weakness in tension and under shock loading limits its use to low pressure steam, air, oil and low speed water fittingsThe above sentence, most probably means （）.Acast iron has weaknessBcast iron can stand up shock loadingCcast iron fittings are only suitable in low pressure situationDeast iron fittings are not suitable in low pressure situation
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单选题You are on a multiple product tanker and carrying methyl acrylate，diethanolamine，and triethylamine. Which statement is TRUE? （）AMethyl acrylate may be loaded in a tank adjacent to diethanolamine but not triethylamineBThe heating coils to the cargo tank loaded with methyl acrylate must be blanked offCValve components made of aluminum，copper，or zinc may not be in contact with the cargoesDEach crew member working on deck must have an emergency escape breathing apparatus
单选题Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service?（）ACopperBCopper and carbonCCarbonDBronze
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单选题The main bearings are provided with thin-walled （）, lined with a copper-lead alloy.Asteel guidesBsteel shellsCsteel bearing capsDpig iron
单选题Ring groove inserts are occasionally used on aluminum alloy piston to（）Areduce the ring groove wear rateBseal against crankcase vaporsClessen the wear on aluminum part of the cylinderDallow for the greater expansion rate of aluminum
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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（）.Ato keep the boats covered at all timesBnot to leave steel or iron tools lying in or near these boatsCto keep an electric charge on the hull at all timesDto rinse these boats regularly with salt water
单选题Cold clearances between the skirt of an aluminum piston and the cylinder liner is about （）Atwice as large as with a cast iron pistonBthe same size as with a cast iron pistonChalf as large as with a cast iron pistonDthe same size as the crown of an aluminum piston
单选题A vessel is constructed with a steel hull and an aluminum superstructure. Which statement is TRUE?（）AThe aluminum will provide greater resistance to the spread of fire by conductionBThe aluminum structure is usually attached to a steel coaming by a method that insulates the two metalsCIf the superstructure is stressed，an aluminum structure requires additional expansion joints to prevent fractureDThe steel at the area of the aluminum-to-steel connection must be closely checked for galvanic corrosion