单选题When current and voltage reach maximum values at the same time, the power factor is()AminimumBmaximumCleadingDlagging

单选题
When current and voltage reach maximum values at the same time, the power factor is()
A

minimum

B

maximum

C

leading

D

lagging


参考解析

解析: 暂无解析

相关考题:

When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____.A.laggingB.leadingC.maximumD.minimum

The Buck(降压式变换器) is a ( ) converter. A.voltage step-upB.current step-downC.current step-upD.resistance

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 generatorB.the alternating current generatorC.the exciterD.the prime moverWhich of the following statements is true according to the passage ?A.With a purely resistance load, the power factor is zeroB.Inductive loads combined with resistance loads produces leading power factorsC.Capacitive loads combined with resistance loads produces lagging power factorsD.With a purely resistance load, the phase angle is zeroWhen 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 muchB.there is a considerable voltage drop in the capacitive load combined with resistance loadC.when the load is the capacitive load combined with resistance load, the voltage drops to zeroD.when the load is the inductive load combined with resistance load, the voltage drop is fairly largeThe exciter must vary with: ① load current ② the power factor, ③ speed change of the prime mover.A.①B.②C.①②D.①②③请帮忙给出每个问题的正确答案和分析,谢谢!

In which two conditions are resumable statements suspended?()A、 when a user exceeds the space quotaB、 when a user session is terminatedC、 when a table that is being accessed by the current transaction is not foundD、 when a user manually suspends the statementE、 when the maximum extents of a segment is reached

What is the effect of using Capacity on Demand on LPARs configured on a managed system?()A、It allows dynamic increase of CPU and memory allocation for all LPARs.B、It allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' and 'Maximum' partition profile values are equal.C、It allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' partition profile values are less than the 'Maximum' values.D、It allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' partition profile values are greater than the 'Maximum' values.

Which two statements are true regarding the return values of property written hashCode and equals methods from two instances of the same class?()A、 If the hashCode values are different, the objects might be equal.B、 If the hashCode values are the same, the object must be equal.C、 If the hashCode values are the same, the objects might be equal.D、 If the hashCode values are different, the objects must be unequal.

单选题Which of the listed items will stop a motor due to a reduction in voltage and restart it when the voltage is restored to normal?()ALow voltage protection circuitBNon-renewable link fuseCRenewable link fuseDLow voltage release circuit

单选题Voltage will always lead current in a/an ()Acapacitive circuitBinductive circuitCmagnetic circuitDresistive circuit

单选题Which is a function of the voltage regulators used with AC generators?()ATo cut out generators when they are no longer requiredBTo cut in additional generators automatically as requiredCTo divide the KW load equally between generators operating in parallelDTo divide reactive current between generators operating in parallel

单选题If the resistance of a circuit is cut in half and the applied voltage is kept constant, the current flow will be ().AdoubledBquadrupledCunchangedDcut in half

单选题With a () load the voltage and current are in phase.Apure resistanceBcapacitiveCinductiveDNone of the above

单选题When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is ()AlaggingBleadingCmaximumDminimum

单选题You are docking a vessel.Wind and current are most favorable when they are().Acrossing your course in the same directionBcrossing your course in opposite directionsCparallel to the pier from aheadDsetting you on the pier

单选题What is an ebb current().AA current at minimum flowBA current coming inCA current going outDA current at maximum flow

多选题Which two statements are true regarding the return values of property written hashCode and equals methods from two instances of the same class?()AIf the hashCode values are different, the objects might be equal.BIf the hashCode values are the same, the object must be equal.CIf the hashCode values are the same, the objects might be equal.DIf the hashCode values are different, the objects must be unequal.

单选题With a purely () load the voltage and current are in phase, giving a power factor of one.AinductiveBresistanceCcombinedDcapacitate

单选题Possible phase relationships between voltage and current in an alternating current circuit include which of the following conditions?()ACurrent and voltage may be in phaseBCurrent may lead the voltageCCurrent may lag the voltageDAll of the above

单选题The alternating current generator supplying a load has a voltage drop resulted from the loadWhen the load has a lagging power factor this voltage drop ().Ais smallBmay be neglectedCis usefulDis considerable

单选题What is the effect of using Capacity on Demand on LPARs configured on a managed system?()AIt allows dynamic increase of CPU and memory allocation for all LPARs.BIt allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' and 'Maximum' partition profile values are equal.CIt allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' partition profile values are less than the 'Maximum' values.DIt allows dynamic increase of CPU and memory allocation for LPARs when the 'Desired' partition profile values are greater than the 'Maximum' values.

单选题A fuse that blows often should be replaced only with a fuse of ().Athe recommended current and voltage ratingBhigher current and voltage ratingChigher current and lower voltage ratingDlower current and higher voltage rating

单选题The easiest way to anchor a vessel in a current is to().Astem the current and make very slow headway when the anchor is droppedBstem the current and be falling aft very slowly when the anchor is droppedCstem the current and endeavor to make neither headway nor sternway when the anchor is droppedDstop all headway through the water and keep the current astern when the anchor is dropped

单选题When two DC generators operate in parallel, they are protected against motorizing by()Ablow out coilsBgovernor relayCunder voltage tripsDreverse current trips

单选题When the voltage remains constant and the resistance is increased in a series circuit, the flow of current ()Aincreases by the square of the original valueBincreasesCremains the sameDdecreases

单选题When the current in a power transmission line is increased, the power loss ()Aincreases as the square of the currentBdecreases as the square root of the currentCremains the same, as it is independent of current flowDincreases in direct proportion as the current

单选题The directive force of a gyrocompass().Aincreases with latitude,being maximum at the geographic polesBdecreases with latitude,being maximum at the geographic equatorCis greatest when a vessel is near the Earth's magnetic equatorDremains the same at all latitudes

单选题When paralleling two AC generators, the frequency of the machine coming on-line, immediately prior to closing its breaker, should be ()Aslightly less than the oncoming generator frequencyBthe same as the bus frequencyCslightly greater than the bus frequencyDthe same as the bus voltage

单选题A transformer in an electric circuit serves to ()Agenerate its own electrical powerBtransform electrical energy into mechanical energyCincrease or decrease circuit voltage as requiredDconvert AC current to DC current