电气工程及其自动化专业英语第一章课文翻译

第一章第一篇sectiong

Two variables u(t) and i(t) are the most basic concepts in an electric circuit, they characterize the various relationships in an electric circuitu(t)与i(t)这两个变量就是电路中最基本的两个变量,它们刻划了电路的各种关系。

Charge and Current

The concept of electric charge is the underlying principle for explaining all electrical phenomena、 Also, the most basic quantity in an electric circuit is the electric charge、 Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C)、电荷与电流电荷的概念就是用来解释所有电气现象的基本概念。也即,电路中最基本的量就是电荷。电荷就是构成物质的原子微粒的电气属性,它就是以库仑为单位来度量的。

We know from elementary physics that all matter is made of fundamental building blocks known as atoms and that each atom consists of electrons, protons, and neutrons、 We also know that the charge e on an electron is negative and equal in magnitude to 1、60210×10 19C, while a proton carries a positive charge of the same magnitude as the electron、 The presence of equal numbers of protons and electrons leaves an atom neutrally charged、我们从基础物理得知一切物质就是由被称为原子的基本构

造部分组成的,并且每个原子就是由电子,质子与中子组成的。我们还知道电子的电量就是负的并且在数值上等于1、602100×10-12C,而质子所带的正电量在数值上与电子相等。质子与电子数量相同使得原子呈现电中性。

We consider the flow of electric charges、 A unique feature of electric charge or electricity is the fact that it is mobile; that is, it can be transferred from one place to another, where it can be converted to another form of energy让我们来考虑一下电荷的流动。电荷或电的特性就是其运动的特性,也就就是,它可以从一个地方被移送到另一个地方,在此它可以被转换成另外一种形式的能量。

When a conducting wire is connected to a battery (a source of electromotive force), the charges are compelled to move; positive charges move in one direction while negative charges move in the opposite direction、 This motion of charges creates electric current、 It is conventional to take the currentflow as the movement of positive charges, that is, opposite to the flow of negative charges, as Fig、l-1 illustrates、This convention was introduced by Benjamin Franklin (l706～l790), the American scientist and inventor、 Although we now know that current in metallic conductors is due to negatively charged electrons, we will follow the universally accepted convention

that current is the net flow of positive charges 、 Thus,

Electric current is the time rate of charge, measured in amperes

(A)、 Mathematically, the relationship among current i , charge

q , and time t is 当我们把一根导线连接到某一电池上时(一种电动势源),电荷被外力驱使移动;正电荷朝一个方向移动而负电荷朝相反

的方向移动。这种电荷的移动产生了电流。我们可以很方便地把电流

瞧作就是正电荷的移动,也即,与负电荷的流动方向相反,如图1－1

所示。这一惯例就是由美国科学家与发明家本杰明－富兰克林引入

的。虽然我们现在知道金属导体中的电流就是由负电荷引起的,但我

们将遵循通用的惯例,即把电流瞧作就是正电荷的单纯的流动。于就

是电流就就是电荷的时率,它就是以安培为单位来度量的。从数学上

来说,电流i 、电荷q 以及时间t 之间的关系就是:

The charge transferred between time t 0 and t is obtained

by integrating both sides of Eq 、 (1-1)、 We obtain 从时间t0

到时间t 所移送的电荷可由方程(1－1)两边积分求得。我们算得:

The way we define current as i in Eq 、 (1-l) suggests that

current need not be a constant-valued function, charge can vary

with time in several ways that may be represented by different

kinds of mathematical functions 我们通过方程(1－1)定义电流的

方式表明电流不必就是一个恒值函数,电荷可以不同的方式随时间而dq i dt

= (1-1)0t

t q idt = (1-2)⎰