电子信息类专业英语,http:/www.cmpbook.com,机械工业出版社同名教材配套电子教案,温丹丽 高源 制作,Passage Two Kirchhoffs Law and Linear Circuit Analysis,机械工业出版社 http:/www.cmpbook.com,1What is Kirchhoffs Current Law? 2What is a node? 3What is Kirchhoffs Voltage Law?,Passage Two Kirchhoffs Law and Linear Circuit Analysis,Words and Expressions consequence 5kCnsikwEns n. 结果，推论 network 5netwE:k n. 网络 node nEud n. 节点 conservation 7kCnsE(:)5veiFEn n. 守恒 circumstance 5sE:kEmstEns n. 境况 algebraical 7AldVi5breiikEl a. 代数的 loop lu:p n. 回路 traverse 5trAvE(:)s v. 穿越，通过 encounter in5kauntE v. 遇到，相遇 impulse 5impQls n. 脉冲 irregular i5rejulE a. 不规则的，无规律的,机械工业出版社 http:/www.cmpbook.com,Passage Two Kirchhoffs Law and Linear Circuit Analysis,ubiquitous ju:5bikwitEs a. 普遍存在的 magnitude 5mAnitju:d n. 大小，数量 sinusoidal 9sainEsRidLl a. 正弦曲线 phasor 5feizE n. 相位复(数)矢量，相量 impedance im5pi:dEns n. 电阻抗 amplitude modulation (AM) 调幅 frequency modulation (FM) 调频 phase angle 相位角 lead network 超前网络 lag network 滞后网络,Passage Two Kirchhoffs Law and Linear Circuit Analysis,Text 1. Kirchhoffs Current Law (KCL) It is a consequence of the work of the German Physicist (18241887) that enables us to analyze an interconnection of any number of elements (voltage sources, current sources, and resistors), as well as other electronic devices. We will refer to any such interconnection as a circuit or a network.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,For a given circuit, a connection of two or more elements shall be called a node. We now present the first of Kerchiefs two laws, his current law (KCL), which is essentially the law of conservation of electric charge： At any node of a circuit, at every instant of time, the sum of the currents into the node is equal to the sum of the currents out of node.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,An alternative, but equivalent, form of KCL can be obtained by considering currents directed into a node to be positive in sense and currents directed out of a node to be negative in sense. Under this circumstance, the alternative form of KCL can be stated as follows： At any node of a circuit, the currents algebraically sum to zero.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,2. Kirchhoffs Voltage Law (KVL) We now present the second of Kirchhoffs laws, the voltage law. To do this, we must introduce the concept of a “loop”. Starting at any node n in a circuit, we form a loop by traversing through elements and returning to the starting node n, and never encountering any other node more than once. Kirchhoffs voltage law (KVL) is: In traversing any loop in any circuit, at every instant of time the sum of the voltages having one polarity equals the sum of the voltages having the opposite polarity.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,An alternative statement of KVL can be obtained by considering voltages across elements that are traversed from plus to minus to be positive in sense and voltages across elements that are traversed from minus to plus to be negative in sense (or vice versa). Under this circumstance, KVL has the following alternative form. Around any loop in a circuit, the voltages algebraically sum to zero.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,3. Sinusoidal Circuits Step and impulse functions are useful in determining the responses of circuits when they are first turned on or when sudden or irregular changes occur in the input. This is called transient analysis. However, to see how a circuit responds to a regular or repetitive inputthe steady-state analysis-function that is by far the most useful is the sinusoid.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,The sinusoid is an extremely important and ubiquitous function. To begin with the shape of ordinary household voltage is sinusoidal, consumer radio transmissions are either amplitude modulation (AM), in which the amplitude of a sinusoid is changed or modulated according some information signal, or frequency modulation (FM), in which the frequency of a sinusoid is modulated.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,We have following conclusions about the sinusoid： 1) If the input of a linear, time-invariant circuit is a sinusoid, then the response is sinusoid of the same frequency. 2) Finding the magnitude and phase angle of a sinusoidal steady-state response can be accomplished with either real or complex sinusoids.,Passage Two Kirchhoffs Law and Linear Circuit Analysis,3) If the output of a sinusoidal circuit teaches its peak, before the input, the circuit is a lead network. Conversely, it is a lag network. 4) Using the concepts of phas or and impedance, sinusoidal circuits can be analyzed in the frequency domain in a manner analogous to resistive circuits by using the phasor versions of KCL, KVL, nodal analysis, mesh analy