Unit 1,Current, Voltage and Resistance,第2/56页,Current，Voltage and Resistance,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,第3/56页,Current, Voltage and Resistance,Unit 1 Current, Voltage and Resistance,电子与通信工程专业英语,Current，Voltage and Resistance,第4/56页,The primary purpose of an electric circuit is to move or transfer charges along specified paths1This motion of charges constitutes an electric currentCurrent flow is represented by the letter symbol, and it is the time rate of change of charge，given by I=dqdt. The basic unit in which current is measured is the ampere (A)An ampere,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,电流，电压和电阻 电路的主要作用是沿着特定路径移动或传送电荷，这种电荷的运动形成了电流。电流用字母I表示，它是电荷随时间的变化率，可表示为I=qd/dt。测量电流的基本单位是安培 (A)。,第5/56页,of current is defined as the movement of one coulomb (628 x 1018 electrons) past any point of a conductor during one second of time. The milliampere(mA) and the microampere (A) units are also used to express a magnitude of current much smaller than the ampere. One milliampere is equivalent to onethousandth of an ampere，and one microampere is equivalent to onemillionth of an ampere.,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,1安培电流的定义即：在1秒钟的时间内有1库仑(6.281018幅电子) 的电量通过导体的任何一点时的电流为1安培。当需要表示比安培小的电流量时，也可用毫安 (mA) 和微安(A) 作单位。1毫安等于千分之一安培，1微安等于百万分之一安培。,第6/56页,We Shall define voltage “across” an element as the work done in moving a unit charge (+1 C) through the element from one terminal to the otherThe term voltage (represented by the letter symbol V ) is commonly used to indicate both a potential difference and an electromotive force. The unit in which voltage is measured,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,将单位电荷(+1C)从元件的一端移动到另一端所做的功定义为元件两端的电压。电压这个术语(用字母符号U表示)通常用来表示电位差和电动势。度量电压的单位是伏特 (V)。,第7/56页,is the volt (V)3. One volt is defined as that magnitude of electromotive force required cause a current of one ampere to pass through a conductor having a resistance of one ohm4Besides the volt, smaller or larger magnitude of voltage are expressed in millivolts,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,使1安培电流流过电阻为1欧姆的导体所需的电动势定义为1伏特。此外，较小或较大数值的电压可以用毫伏(mV)、微伏(V)或千伏(kV)表示。,(mV), microvolts (V) or kilovolts (kv).,第8/56页,Resistors restrict the flow of electric current，for example， a resistor is placed in series with a light emitting diode (LED) to limit the current passing through the LED5. The value of resistor is called resistance and is represented by the letter symbol R Resistance is measured in ohms；the symbol of ohm is an omega . One ohm is defined as that amount of resistance that will limit the current in a conductor is one ampere when the voltage applied to the conductor is one volt61 is quite small so resistor values are often given in kiloohm (k) or megohm (M).,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,电阻器阻碍电流的流动，比如与发光二极管(LED)串联的电阻器就限制了流过LED的电流。电阻器的阻碍数值叫电阻，用字母符号R表示。电阻用欧姆来度量，欧姆的符号是 。1欧姆的定义即：1伏特的电压施加在导体上产生了1安培的电流，此时该导体的电阻值为1欧姆。1欧姆单位很小，所以电阻值常常用千欧(k )和兆欧/ 百万欧姆(M )来表示。,第9/56页,Ohms Law” is one of the fundamental laws of electronics, and pertains to the relationship between current, voltage and resistance in an electrical conductor. This relationship states that “Current=VoltageResistance“. Ohms Law states that the ratio of the voltage between the ends of a wire and the current flowing in it is equal to the resistance of the wire. The usual way of expressing this in mathematical terms is “I=U/R”，and “U=IR ” or “R=U/I“ are,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,欧姆定律是电子学中最基本的定律之一，用来表示导体中电流、电压和电阻之间的关系。此关系可用公式表示为“电流= 电压/ 电阻“。欧姆定律阐述了导线两端的电压和流过它的电流的比率等于导线的电阻。常用来描述欧姆定律的数学表达式有“I=U/R”，“U=IR”或“R=U/I”。,also used.,第10/56页,New words and phrases,current krnt adj. 现在的；通用的 n.趋势；（水、气、电）流 constitute knstitju:t vt. 组成，构成；任命；建立 represent ,reprizent vt. 表现；代表；表示vi. 提出异议；代表 voltage vultid n. 电 电压 diode daiud n. 电 二极管 circuit s：kit n电路 transfer traensf: vt转移，移动 charge ta:d n. 费用；负载；电荷vt.使充电 vi. 索价；充电； specify spesifai vt. 指定；列举；详细说明；把列入说明书 symbol simbl n符号；象征,Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,第11/56页,ampere mpe n.安培 milliampere ,milimp n. 电毫安 microampere ,maikrump n. 微安培；微安 coulomb ku：lm n电库仑 magnitude mgnitju：d n数量，大小 element elimnt n元素，元件 terminal t：minl n终端；接线端 ohm um n电欧姆 kiloohm ki：lu m n电千欧(姆) megohm megum n电兆欧(姆),Current，Voltage and Resistance,电子与通信工程专业英语,Unit 1 Current, Voltage and Resistance,第12/56页,millivolt milivult n. 电毫伏（特） microvolt maikruvult n. 微伏 kilovolt kiluvult n. 千伏特 pertain p:tein, p- vi. 适合；属于；关于 resistor rizi st n电 电阻器 diode daiud n二极管 ratio reiiu, -u n比，比率 be represented by 用表示 be equivalent to 等于 in series