单选题Voltage will always lead current in a/an （）Acapacitive circuitBinductive circuitCmagnetic circuitDresistive circuit
单选题
Voltage will always lead current in a/an （）
A
capacitive circuit
B
inductive circuit
C
magnetic circuit
D
resistive circuit
参考解析
解析：
暂无解析
相关考题：
______it may lead to, they always pursue the profit maximization. A.No matter whereB.No matter whatC.No matter how
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
下列哪些测试不须考虑输入电压的偏差() A．Input TestB．Touch current TestC．Working Voltage MeasurementD．Discharge Test
Current measuring instruments must always be connected in ______.A.series with a circuitB.parallel with a circuitC.series-parallel with a circuitD.delta with the shunt
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！
A switchboard for an AC electrical system requires the use of which of the following devices?A.Frequency meter.B.Ohmmeter.C.Induction voltage regulator.D.Current transformer governor.
We should always keep in mind that ______ decisions often lead to bitter regrets.A.hastyB.instantC.promptD.rapiD.
单选题The output voltage of a three-phase alternator is regulated by the （）.AAC voltage to the armatureBAC voltage to the fieldCDC voltage to the armatureDDC voltage to the field
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The （） is a measure of the phase difference between voltage and current and is expected as the cosine of phase angle.ApowerBefficiencyCeffective powerDpower factor
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Line losses in a distribution circuit are kept to a minimum by （）.Aadding rubber insulation conductors to the circuitBusing higher current and lower voltage increasing theCnumber of thermal relays in the circuitDusing higher voltage and lower current
单选题With a purely （） load the voltage and current are in phase, giving a power factor of one.AinductiveBresistanceCcombinedDcapacitate
单选题Self-excited a-cgenerator with "error operated" voltage control systems draw the full excitation power for the machine terminalsThis dispenses with the current transformers, reactors and capacitors necessary for accurate compounding, but renders the excitation system vulnerable to variations in its output voltageWhich of the following is correct about the generator mentioned according to the sentences above （）.AIt consumes no excitation powerBIt has current transformersCComponents are needed for accurate compoundingDIts excitation system is vulnerable to voltage variations
单选题The power factor is a measure of the phase difference between voltage and current and is expressed as the（） of the phase angle.AsineBcosineCtangentDcotangent
单选题Reduced voltage applied to a motor during the starting period will （）.Aresult in decreased acceleration time onlyBlower the starting current and increase accelerating timeCcause a greater starting torqueDincrease the starting current and pump capacity
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Which of the following statements is true concerning simple parallel resistance circuits?（）AThe total current flow equals the sum of the individual currentsBThe total current flow equals the reciprocal of the sum of the individual currentsCThe total resistance equals the sum of the individual resistanceDThe total voltage equals the sum of the individual voltages across each resistance
单选题The initial voltage of self-excitation generator set up by（）Aresidual magnetismBvoltage regulatorCelectrical current for excitationDthe other running generator
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When two DC generators operate in parallel, they are protected against motorizing by（）Ablow out coilsBgovernor relayCunder voltage tripsDreverse current trips
单选题Current measuring instruments must always be connected in （）Aseries with a circuitBparallel with a circuitCseries-parallel with a circuitDdelta with the shunt
单选题Which of the following statements concerning a simple parallel resistance circuit is correct?（）AThe voltage drop across each resistor is the sameBThe total current flow equals the reciprocal of the sum of the individual currentsCThe total resistance equals the sum of the individual resistancesDThe total voltage equals the sum of the individual voltages across each resistance
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