電子與通信技術(shù)專業(yè)英語(yǔ)Unit-I-3課件

UnitⅠBasicKnowledgeofElectronicsLesson3AC,DCandElectricalSignals

NewWordspositive

['p?z?tiv]a.正的frequency

['frikw?nsi]

n.頻率measure['me??]

v.n

測(cè)量device[di'vais]

n.裝置，設(shè)備label['leibl]n.標(biāo)簽

v.貼標(biāo)簽于；amplitude

['?mplitju:d]

n.振幅period['p??r??d]

n.時(shí)期，周期oscilloscope[?'sil?usk?up]n.示波器millisecond['mili,sek?nd]n.毫秒microsecond['mili,sek?nd]n.微秒PhrasesandExpressionsAlternatingCurrent交流電DirectCurrent直流電powersupply

電源electroniccircuit

電子電路electricalsignal電信號(hào)peakvoltage峰值電壓peak-peakvoltage峰-峰值電壓effectivevalue有效值Notes1.TherateofchangingdirectioniscalledthefrequencyoftheACanditismeasuredinhertz(Hz)whichisthenumberofforwards-backwardscyclespersecond.hertz(Hz)：n.赫茲(電學(xué)頻率單位)；赫(茲),每秒周數(shù)[頻率單位]【大寫(xiě)】赫茲(德國(guó)物理學(xué)家)n.赫茲(電學(xué)頻率單位)；【大寫(xiě)】赫茲(德國(guó)物理學(xué)家)cyclespersecond：每秒循環(huán)數(shù)這種方向變化的速率稱為交流信號(hào)的頻率，單位是赫茲，它表示一秒內(nèi)周期性變化的次數(shù)。2.Thevoltage-timegraphonthefig.3-4showsvariouspropertiesofanelectricalsignal.voltage-timegraph：電壓時(shí)間曲線圖3－4的電壓－時(shí)間圖顯示了一個(gè)電信號(hào)的各種特性。3.Thediagramshowsasinewavebutthesepropertiesapplytoanysignalwithaconstantshape.sinewave：n.正弦波cosinewave：n.余弦波該圖顯示了一個(gè)正弦波，但這些特性適用于具有恒定形狀的任何信號(hào)。4.Timeperiodisthetimetakenforthesignaltocompleteonecycle.Itismeasuredinseconds(s),buttimeperiodstendtobeshortsomilliseconds(ms)andmicroseconds(μs)areoftenused.1ms

=

0.001sand1μs

=

0.000001s.milliseconds(ms)：n.毫秒；微秒

microseconds(μs)：micro-secondn：微秒周期是完成一個(gè)周期的信號(hào)所需要的時(shí)間。單位是秒，但是周期往往非常短，所以常用毫秒（ms）和微秒(μs)。1ms=0.001s，1μs=0.000001s。5.1kHz

=

1000Hzand1MHz

=

1000000Hz.

千赫（kHz）和兆赫（MHz）。6.Frequency＝1/timeperiodandtimeperiod=1/frequency.timeperiod：周期頻率＝1/周期，周期＝1/頻率TranslationofTextsLesson3AC,DCandElectricalSignalsAlternatingCurrent(AC)AlternatingCurrent(AC)flowsoneway,thentheotherway,continuallyreversingdirection.AnACvoltageiscontinuallychangingbetweenpositive(+)andnegative(-).TherateofchangingdirectioniscalledthefrequencyoftheACanditismeasuredinhertz(Hz)whichisthenumberofforwards-backwardscyclespersecond.第3課交流電，直流電以及電信號(hào)交流電交流電流的方向從一個(gè)方向轉(zhuǎn)換成另一個(gè)方向，持續(xù)不斷的轉(zhuǎn)換（如圖3－1和圖3－2所示）。交流電壓會(huì)持續(xù)不斷的在正負(fù)兩個(gè)極性之間交替變化。這種方向變化的速率稱為交流信號(hào)的頻率，單位是赫茲，它表示一秒內(nèi)周期性變化的次數(shù)。AnACsupplyissuitableforpoweringsomedevicessuchaslampsandheatersbutalmostallelectroniccircuitsrequireasteadyDCsupply.

交流電源適用于給一些設(shè)備供電，如燈和加熱器，但幾乎所有的電子電路都需要一個(gè)穩(wěn)定的直流電。DirectCurrent(DC)DirectCurrent(DC)alwaysflowsinthesamedirection,butitmayincreaseanddecrease.ADCvoltageisalwayspositive(oralwaysnegative),butitmayincreaseanddecrease.ElectroniccircuitsnormallyrequireasteadyDCsupplywhichisconstantatonevalue.Cells,batteriesandregulatedpowersuppliesprovidesteadyDCwhichisidealforelectroniccircuits.Lamps,heatersandmotorswillworkwithanyDCsupply.

直流電直流電流總是向同一個(gè)方向流動(dòng)，但它可能增大或者減小。直流電的方向總是正的（或者總是負(fù)的），但它也可能增大或者減?。ㄈ鐖D3－3所示）。電子電路通常需要一個(gè)具有定值的穩(wěn)定的直流電源。干電池、蓄電池（組）和穩(wěn)壓電源能提供對(duì)于電子電路來(lái)說(shuō)理想的、穩(wěn)定的直流電。在直流電源作用下，電燈，加熱器和發(fā)動(dòng)機(jī)將可以正常工作。PropertiesofelectricalsignalsAnelectricalsignalisavoltageorcurrentwhichconveysinformation,usuallyitmeansavoltage.Thetermcanbeusedforanyvoltageorcurrentinacircuit.

電信號(hào)的特性電信號(hào)是傳送信息的電壓或者電流，通常是指電壓。這個(gè)術(shù)語(yǔ)可以被用于電路里任何一個(gè)電壓或者電流。Thevoltage-timegraphonthefig.3-4showsvariouspropertiesofanelectricalsignal.Inadditiontothepropertieslabeledonthegraph,thereisfrequencywhichisthenumberofcyclespersecond.Thediagramshowsasinewavebutthesepropertiesapplytoanysignalwithaconstantshape.

圖3－4的電壓－時(shí)間圖顯示了一個(gè)電信號(hào)的各種特性。除了圖上標(biāo)明的那些特性以外還有頻率，它表示每秒鐘的周期數(shù)。該圖顯示了一個(gè)正弦波，但這些特性適用于具有恒定形狀的任何信號(hào)。Amplitudeisthemaximumvoltagereachedbythesignal.Itismeasuredinvolts,V.

振幅是信號(hào)所達(dá)到的最大電壓。單位是伏特，V。Peakvoltageisanothernameforamplitude.

峰值電壓是振幅的另一個(gè)名稱。Peak-peakvoltageistwicethepeakvoltage(amplitude).Whenreadinganoscilloscopetraceitisusualtomeasurepeak-peakvoltage.

峰－峰值電壓是峰值電壓（振幅）的兩倍。當(dāng)對(duì)示波器上的軌跡進(jìn)行讀數(shù)的時(shí)候，我們通常測(cè)量峰－峰值電壓。Timeperiodisthetimetakenforthesignaltocompleteonecycle.Itismeasuredinseconds(s),buttimeperiodstendtobeshortsomilliseconds(ms)andmicroseconds(μs)areoftenused.1ms

=

0.001sand1μs

=

0.000001s.

周期是完成一個(gè)周期的信號(hào)所需要的時(shí)間，單位是秒。但是周期往往非常短，所以常用毫秒（ms）和微秒(μs)。1ms=0.001s，1μs=0.000001s。Frequencyisthenumberofcyclespersecond.Itismeasuredinhertz(Hz),butfrequenciestendtobehighsokilohertz(kHz)andmegahertz(MHz)areoftenused.1kHz

=

1000Hzand1MHz

=

1000000Hz.1kHz=1000Hzand1MHz=1000000Hz。Frequency＝1/timeperiodandtimeperiod=1/frequency.

頻率是每秒的周期數(shù)。單位是赫茲（Hz），但頻率往往比較高，所以常用千赫（kHz）和兆赫（MHz）。頻率＝1/周期，周期＝1/頻率。AnothervalueusedistheeffectivevalueofAC.Thisisthevalueofalternatingvoltageorcurrentthatwillhavethesameeffectonaresistanceasacomparablevalueofdirectvoltageorcurrentwillhaveonthesameresistance.

另一個(gè)常用的值是有效值，電壓或電流有效值作用于電阻，與相同大小的直流電壓或電流作用于相同大小的電阻等效。ExercisesⅠ.WriteT(True)orF(false)besidethefollowingstatementsaboutthetext.1.DirectCurrent(DC)flowsoneway,thentheotherway,continuallyreversingdirection.2.AlternatingCurrent(AC)alwaysflowsinthesamedirection.

3.Amplitudeistheminimumvoltagereachedbythesignal.4.Peak-peakvoltageistwicethepeakvoltage(amplitude).5.TheeffectivevalueofACisthevalueofalternatingvoltageorcurrentthatwillhavethesameeffectonaresistanceasacomparablevalueofdirectvoltageorcurrentwillhaveonthesameresistance.Ⅱ.Fillinthemissingwordsaccordingtothetext.1.AnACvoltageiscontinuallychangingbetween

and

.2.ElectroniccircuitsnormallyrequireasteadyDCsupplywhichis

onevalue.3.Cells,batteriesandregulatedpowersuppliesprovide