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单选题
The unit of electrical resistance is the （）
A
ampere
B
volt
C
watt
D
ohm
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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.What is the benefit of the revolution mentioned in the first paragraph?A:With a flip of switch,electricity can be transmitted,B:Other American cities can benefit from the high-performance cables.C:Great amounts of power can be conserved.D:Detroit will first receive electricity transmitted by the new electrical cables.
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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.According tothe last paragraph,which of the following statements is NOT true?A:Other cities hope they can also conserve power.B:Other cities hope they can use superconducting cables soon.C:Superconductors waste less power because of their low resistance.D:The Frisbie experiment is not successful.
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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.What element enables the ceramic tape to lower its temperature?A:Copper. B:Liquid nitrogen.C:Clay. D:Calcium.
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共用题干
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MRC是什么的缩写？（）A、Modular Radio ConnectB、Modular Resistance CabinetC、Modular Radio CabinetD、Modular Resistance Connect
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Which logical unit number must be configured on an interface using PPP encapsulation?（）A、unit 0B、unit 1C、unit 100D、unit 255
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According to Ohm’s Law， which of the following is correct？（）A、As voltage increases， resistance decreasesB、As amperage decreases， resistance decreasesC、As resistance decreases， amperage increasesD、As resistance increases， voltage increases
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增强型电源系统是如何同MCDU相连？A、直接通过每一个GCUB、通过GAPCU和CFDIUC、通过CFDIU同EGIU(ELECTRICAL GENERATION INTERFACE UNIT)
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单选题Grease coatings on electrical contact surfaces increase contact resistance and should be removed with a/an （）.A
small wire brushB
compressed air jetC
clean dry clothD
10% solution carbon solvent and water
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单选题If a voltmeter is connected across a line, it must be protected with a（）A
shuntB
high-resistance coil in the armature circuitC
low-resistance coil in the armature circuitD
shunt and a coil of high resistance
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单选题For practical purposes, in a simple series circuit, the source voltage will be dropped across one resistor if it has（）.A
half the resistance of the other resistorB
a resistance equal to the otherC
at least ten times the resistance of the otherD
a partial short circuit
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单选题When a rescuer finds an electrical burn victim in the vicinity of live electrical equipment or wiring，his first step is to（）.A
flush water over any burned area of the patientB
apply ointment to the burned areas on the patientC
get assistance to shut down electrical power in the areaD
remove the patient from the vicinity of the live electrical equipment or wiring
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单选题In general, the oil mist detectors include a built-in heating unit and a compact plug for electrical connectionThe function of heating unit is to （）A
avoid false alarms as a result of condensing water vaporB
avoid danger of frost under very cold weatherC
reduce the viscosity of the crankcase atmosphere in order to improve the fluidityD
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考题
单选题According to Ohm’s Law， which of the following is correct？（）A
As voltage increases， resistance decreasesB
As amperage decreases， resistance decreasesC
As resistance decreases， amperage increasesD
As resistance increases， voltage increases
考题
单选题Moisture absorbed in the windings or condensed on the surface of electrical machinery insulation （）A
is good for long term preserving since most insulation is organic and contains some amountB
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will enhance insulation resistance only if it is fresh water and contains no saltD
reduces the amount of current supplied or drawn by the machine so horsepower is limited
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The FIRST thing to do to ensure that a refrigeration unit will not start while undergoing repairs, is to （）.A
secure and tag the electrical circuitB
place a crow bar in the flywheel of the unitC
inform all persons in the area not to start the unitD
make a log book entry
考题
单选题Which of the following statements is true concerning simple parallel resistance circuits?（）A
The total current flow equals the sum of the individual currentsB
The total current flow equals the reciprocal of the sum of the individual currentsC
The total resistance equals the sum of the individual resistanceD
The total voltage equals the sum of the individual voltages across each resistance
考题
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
考题
单选题Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.A
increase in resistance with increased temperatureB
increase in resistance with decreased temperatureC
decrease in resistance with increased temperatureD
increase in conductance with increased temperature
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