電子與通信技術(shù)專業(yè)英語Unit-I-課件3

1、劉 騁 蔡 靜 劉小芹 主編電子與通信技術(shù)專業(yè)英語（第5版）高職高專電子信息類“十三五”規(guī)劃教材English on Electronic and Telecommunication Technology01Unit Basic Knowledge of ElectronicsLesson 3 AC, DC and Electrical SignalsUnit New Wordspositive pztiv a. 正的frequency frikwnsi n. 頻率measure me v.n 測量device divais n. 裝置，設(shè)備label leibl n. 標(biāo)簽 v. 貼標(biāo)簽于；

2、New Wordsamplitudemplitju:d n. 振幅periodprd n. 時(shí)期，周期oscilloscopesiluskup n. 示波器millisecond mili,seknd n. 毫秒microsecond mili,seknd n. 微秒Phrases and ExpressionsAlternating Current 交流電Direct Current 直流電power supply 電源electronic circuit 電子電路Phrases and Expressionselectrical signal 電信號(hào)peak voltage 峰值電壓pea

3、k-peak voltage 峰-峰值電壓effective value 有效值A(chǔ)lternating Current (AC) flows one way, then the other way, continually reversing direction. An AC voltage is continually changing between positive (+) and negative (-). The rate of changing direction is called the frequency of the AC and it is measured in her

4、tz (Hz) which is the number of forwards-backwards cycles per second. Lesson 3 AC, DC and Electrical Signals Alternating Current (AC) Chinese Translation of Texts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31和圖32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)。第3課 交流電，直流電以及電信號(hào)Chinese Transla

5、tion of TextsAn AC supply is suitable for powering some devices such as lamps and heaters but almost all electronic circuits require a steady DC supply. 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。Chinese Translation of TextsChinese Translation of Texts Direct Current (DC) Direct Current (DC) always

6、 flows in the same direction, but it may increase and decrease. A DC voltage is always positive (or always negative), but it may increase and decrease. Electronic circuits normally require a steady DC supply which is constant at one value. Cells, batteries and regulated power supplies provide steady

7、 DC which is ideal for electronic circuits. Lamps, heaters and motors will work with any DC supply. Chinese Translation of Texts 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D33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)于電子電路來說理想的、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。Chinese Transl

8、ation of Texts Properties of electrical signals An electrical signal is a voltage or current which conveys information, usually it means a voltage. The term can be used for any voltage or current in a circuit. 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)語可以被用于電路里任何一個(gè)電壓或者電流。Chinese Translation of TextsThe voltag

9、e-time graph on the fig.3-4 shows various properties of an electrical signal. In addition to the properties labeled on the graph, there is frequency which is the number of cycles per second. The diagram shows a sine wave but these properties apply to any signal with a constant shape. Chinese Transla

10、tion of Texts圖34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)。Chinese Translation of TextsAmplitude is the maximum voltage reached by the signal. It is measured in volts, V. 振幅是信號(hào)所達(dá)到的最大電壓。單位是伏特，V。 Chinese Translation of TextsPeak voltage is another name for amplitud

11、e. 峰值電壓是振幅的另一個(gè)名稱。Chinese Translation of TextsPeak-peak voltage is twice the peak voltage (amplitude). When reading an oscilloscope trace it is usual to measure peak-peak voltage. 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，我們通常測量峰峰值電壓。Chinese Translation of TextsTime period is the time taken for the signal t

12、o complete one cycle. It is measured in seconds (s), but time periods tend to be short so milliseconds (ms) and microseconds (s) are often used. 1ms=0.001s and 1s=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(s)。1ms =0.001s，1s=0.000001s。Chinese Translation of Texts Frequency is the numb

13、er of cycles per second. It is measured in hertz (Hz), but frequencies tend to be high so kilohertz (kHz) and megahertz (MHz) are often used. 1kHz=1000Hz and 1MHz=1000000Hz. 1kHz=1000Hz and 1MHz=1000000Hz。Frequency1/ time period and time period=1/ frequency.Chinese Translation of Texts頻率是每秒的周期數(shù)。單位是赫

14、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。Chinese Translation of Texts Another value used is the effective value of AC. This is the value of alternating voltage or current that will have the same effect on a resistance as a comparable value of direct voltage or current will have on the same r

15、esistance. Chinese Translation of Texts 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。NotesThe rate of changing direction is called the frequency of the AC and it is measured in hertz (Hz) which is the number of forwards-backwards cycles per second. 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】

16、赫茲(德國物理學(xué)家) n.赫茲(電學(xué)頻率單位)；【大寫】赫茲(德國物理學(xué)家) cycles per second：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)。1NotesThe voltage-time graph on the fig.3-4 shows various properties of an electrical signal. voltage-time graph：電壓時(shí)間曲線圖34的電壓時(shí)間圖顯示了一個(gè)電信號(hào)的各種特性。2NotesThe diagram shows a sine wave but these propertie

17、s apply to any signal with a constant shape. sine wave： n.正弦波cosine wave： 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)。3NotesTime period is the time taken for the signal to complete one cycle. It is measured in seconds (s), but time periods tend to be short so milliseconds (ms) and microseconds (s) are often

18、 used. 1ms=0.001s and 1s=0.000001s. milliseconds (ms)：n.毫秒；微秒microseconds (s)：micro-second n：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(s)。1ms =0.001s，1s=0.000001s。4Notes1kHz=1000Hz and 1MHz=1000000Hz. 千赫（kHz）和兆赫（MHz）。5NotesFrequency1/ time period and time period=1/ frequency. time period：周期頻

19、率1/周期，周期1/頻率6Exercises 1. Write T(True) or F(false) beside the following statements about the text.a. Direct Current (DC) flows one way, then the other way, continually reversing direction.b. Alternating Current (AC) always flows in the same direction. c. Amplitude is the minimum voltage reached by

20、the signal.d. Peak-peak voltage is twice the peak voltage (amplitude).e. The effective value of AC is the value of alternating voltage or current that will have the same effect on a resistance as a comparable value of direct voltage or current will have on the same resistance.Exercises 1. Write T(Tr

21、ue) or F(false) beside the following statements about the text.a. Direct Current (DC) flows one way, then the other way, continually reversing direction.b. Alternating Current (AC) always flows in the same direction. c. Amplitude is the minimum voltage reached by the signal.d. Peak-peak voltage is t

22、wice the peak voltage (amplitude).e. The effective value of AC is the value of alternating voltage or current that will have the same effect on a resistance as a comparable value of direct voltage or current will have on the same resistance.FFFTTExercises2. Fill in the missing words according to the

23、 text.a. An AC voltage is continually changing between and .b. Electronic circuits normally require a steady DC supply which is one value.c. Cells, batteries and regulated power supplies provide which is ideal for electronic circuits.d. In addition to the properties labeled on the graph, there is fr

24、equency which is the number of per second.e. When reading an oscilloscope trace, it is usual to measure voltage.Exercises2. Fill in the missing words according to the text.a. An AC voltage is continually changing between positive and negative.b. Electronic circuits normally require a steady DC supply which is constant at one value.c. Cells, batteries and regulated power supplies provide steady DC which is ideal for electronic circuits.d. In addition to the properties labeled on the graph, there is