网友您好， 请在下方输入框内输入要搜索的题目：
题目内容
（请给出正确答案）
单选题
Copper is often used as an electrical conductor because it （）.
A
has high resistance at low temperatures
B
has a highly polished surface
C
is able to pass current with little opposition
D
holds insulation together well
参考答案
参考解析
解析：
暂无解析
更多 “单选题Copper is often used as an electrical conductor because it （）.A has high resistance at low temperaturesB has a highly polished surfaceC is able to pass current with little oppositionD holds insulation together well” 相关考题
考题
Why do the critics criticize advertisers?A． Because advertisers often brag.B． Because critics think advertisement is a "waste of money".C． Because customers are encouraged to buy more than necessary.D． Because customers pay more.
考题
Dry powder is used to put out ________A.electrical fireB.oil fireC.common firesD.all kinds of fires
考题
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.
考题
Canadian media often cite excessive fishing by overseas fleets, primarily because of ______.
考题
Because of ______，air ducts used aboard ships are often very small and have sharp curves and bends．A.high levelB.overflow spacesC.cargo tankD.space constraints
考题
Silver is the best conductor of electricity, copper ___________ it closely.A.followed
B.to follow
C.following
D.being followed
考题
Why do the critics criticize advertisers?__________A.Because advertisers often brag
B.Because critics think advertisement is a "waste of money"
C.Because customers are encouraged to buy more than necessary
D.Because customers pay more
考题
共用题干
第二篇Superconducting Ceramic（陶瓷）An underaround revolution beqins this winter. With the flip（轻击）of a switch, 30,000 homes in one part of Detroit will soon become the first in the country to receive electricity transmitted by ice-cold high-performance cables.Other American cities are expected to follow Detroit's example in the years ahead,which could conserve enormousamounts of rower.The new electrical cables at the Frisbie power station in Detroit are revolutionary because they are made of superconductors.A superconductor is a material that transmits electricity with little or no resistance.Resistance is the degree to which a substance resists electric current.All common electrical conductors have a certain amount of electrical resistance.They convert at least some of the electrical energy passing through them into waste heat.Superconductors don't.No one understands how superconductivity works.It just does.Making superconductors isn't easy.A superconducting material has to be cooled to an extremely low temperature to lose its resistance.The first superconductors,made more than 50 years ago,had to be cooled to -263 degrees Celsius before they lost their resistance.Newer superconducting materials lose their resistance at-143 degrees Celsius.The superconductors cable installed at the Frisbie station is made of a ceramic material that contains copper,oxygen,bismuth（秘）,strontium（锶）and calcium (钙）.A ceramic is a hard,strong compound made from clay or minerals.The superconducting ceramic has been fashioned into a tape that is wrapped lengthwise around a long tube filled with liquid nitrogen.Liquid nitrogen is supercold and lowers the temperature of the ceramic tape to the point where it conveys electricity with zero resistance.The United States loses an enormous amount of electricity each year to resistance. Because cooled superconductors have no resistance,they waste much less power. Other cities are watching the Frisbie experiment in the hope that they might switch to superconducting cable and conserve power,too.Compared to common electrical conductors,superconductorsA:have little or no electrical resistance.B:can be used for a long time.C:are not energy-efficient.D:can be made easily.
考题
Silver is the best conductor of electricity,copper__________it closely.A.followed
B.following
C.to follow
D.being followed
考题
CO2 and Halon extinguishers are used for electrical fire, as well as （）fire.A、commonB、oilC、electricalD、chemical
考题
The "1000" in 1000BaseT cabling represents which of the following?（）A、The theoretical maximum cable lengthB、The theoretical maximum bandwidthC、The theoretical port limit of the cableD、The quality level of the copper wiring used
考题
Which of the following tools should be used to report current network status and is often used to check the reliability of a network？（）A、 netpmonB、 netstatC、 nfsstatD、 vmstat
考题
单选题Gear-type flexible couplings are often used in diesel engine drive trains because they（）A
require no lubrication under normal operating conditionsB
compensate for gross misalignment in the drive trainC
are able to transmit high torque ,even where slight misalignment existsD
will rapidly disconnect the engine from the line shaft
考题
单选题The height of a VHF radio antenna is more important than the power output wattage of the radio because（）.A
VHF communications are basically line of sightB
the air is more dense the higher you goC
salt water is a poor conductor of soundD
sea water absorbs the radiated energy
考题
单选题（）on board ship are used to control and distribute the electrical energy generated by generators.A
GovernorsB
AlternatorsC
BlackboardsD
Switchboards
考题
单选题Which of the listed devices is used to measure pressure and convert it to an electrical signal?（）A
TransducerB
ReducerC
TransformerD
Rectifier
考题
单选题Nylon rope is often used in the makeup of a towline because it（）.A
floatsB
stretchesC
handles easilyD
resists rot
考题
单选题________are often used in pronunciation practice because they are fun and motivating. Also the relaxing atmosphere helps students overcome inhibition. Students should be given time to practice on their own for a few minutes before they are asked to perform in front of the whole class.A
Tongue twistersB
Meaningful contextsC
Filling in the blanksD
Listening and repeating
考题
单选题Only one of the following statements is false, according to what was said. Which one is it?A
Researchers said estimates of atomic bomb survivors' radiation doses are accurate.B
Doubts about the accuracy of methods used to collect exposure data in 1945 prompted the review.C
The earlier methods were unable to detect radioactive fallout because the researchers could not get close to the bomb site.D
The amount of nickel in each copper sample can be correlated to the intensity of radiation exposure at the site.
考题
单选题In context, which version of the underlined portion of sentence 5 (reproduced below) is the best?Because the victims often get depression because of their symptoms, other doctors used to bell it was psychological.A
those symptoms wereB
their depression wasC
the victims wereD
chronic fatigue syndrome wasE
they were
考题
多选题Which of the following multimeter settings should only be used when there is no electrical flow through the part being tested? （）(Select TWO).AAmpereBContinuityCVoltDResistanceEWattage
考题
单选题Seamless mild steel is used for steam (also copper for moderate pressure and temperature), h-pair, feed discharge and all oil fuel pressure pipingsAccording to the above sentence, which of the following statements is not true?（）A
Both seamless mild steel and copper may be used for middle pressure steamB
hpair means high pressure airC
The feed piping of the boilers can be made of seamless mild steelD
All oil pipings are made of mild steel
考题
单选题This machine （）out of order very often, but now it works well.A
is used to beB
was used to beC
used to beD
was used to
考题
单选题Which of the following statements is true concerning Halon 1301 fire extinguishing equipment?（）A
The agent is considered nontoxic at room temperature in low concentrationsB
The agent is less effective than carbon dioxideC
Halon primarily extinguishes the fire by coolingD
The agent cannot be used on electrical fires because it leaves a residue
热门标签
最新试卷
