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Basic Theory of Circuits

Basic Theory of Circuits. SEIEE Shanghai Jiao Tong University 2009.9. Introduction. Course Title: Basic Theory of Circuits Periods/ Credits: 72/4 Prerequisites: Advanced math; General physics Lecturer: Associate Professor Li Ping Email address: liping@sjtu.edu.cn

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Basic Theory of Circuits

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  1. Basic Theory of Circuits SEIEE Shanghai Jiao Tong University 2009.9 Basic Theory of Circuits, SJTU

  2. Introduction Course Title: Basic Theory of Circuits Periods/ Credits: 72/4 Prerequisites: Advanced math; General physics Lecturer: Associate Professor Li Ping Email address:liping@sjtu.edu.cn Lecture time and classroom:东下院205 Wed34;Fri12 Tutorial arrangement: Website:http://ee.sjtu.edu.cn/po/Class-web/dianlu-jichu/index.htm http://eelab.sjtu.edu.cn/dl/ Assessment: Basic Theory of Circuits, SJTU

  3. Course objective: The aim and task for this course is to help the students to grasp the circuits concepts correctly, grasp the basic rules and analyzing methods, which provides a solid basis for further study Basic Theory of Circuits, SJTU

  4. Topics covered: • Basic concepts • Lumped-parameter circuits • Variables • Circuit elements • Circuit model • Basic rules Basic Theory of Circuits, SJTU

  5. Topics covered: • Analysis of linear resistive network • Mesh analysis • Nodal analysis • Loop analysis • Cut sets analysis • Analysis theorems Basic Theory of Circuits, SJTU

  6. Topics covered: • Analysis of linear dynamic circuit • first-order RC, RL circuit • Step response and impulse response • second-order RLC circuit • Analysis method in frequency domain Basic Theory of Circuits, SJTU

  7. Topics covered: • Analysis of sinusoidal stable state • sinusoidal variable and phastor • sinusoidal stable state response • Circuit analysis in phasor model • AC power analysis • Magnetically coupled circuits • Concept of balanced three-phase circuits Basic Theory of Circuits, SJTU

  8. Topics covered: • Analysis of two-port network • network parameter • Interconnection of networks • Reciprocal network • analysis of the terminated two-port circuit Basic Theory of Circuits, SJTU

  9. Place of Electrical Circuits in Modern Technology The design of the circuits has 2 main objectives: 1)  To gather, store, process, transport, and present information. 2)  To distribute and convert energy between various forms. The study of circuits provides a foundation for areas of electrical engineering such as: • Communication system • Computer system • Control system • Electronics • Electromagnetic • Power systems • Signal processing Basic Theory of Circuits, SJTU

  10. This is what we emphasize on, Since it provides the foundation for understanding the interaction of signal solution. Circuits (given) Excitation (given) Response (unknown) Circuit Analysis In contrast to analysis, a design problem may have no solution or several solutions, Circuits (unknown) Response (given) Excitation (given) Circuit synthesis (design) Circuit Analysis Circuit Theory Circuit Synthesis Motivation for doing this course As a student of SEIEE, you should : 1)  Understand the main principles of how electrical equipment operates. So you can operate or maintain electrical systems. 2)  Have a broad enough knowledge base to lead further study. About the course Basic Theory of Circuits, SJTU

  11. Resistance circuits analysis The course includes: Dynamic circuits analysis Sinusoidal steady state Reference Books 1) Fundamentals of Electric Circuits Charles K Alexander TsingHua Uni Press (photocopy version) 2) The Analysis and Design of Linear Circuits Roland E.Thomas, Albert J.Rosa—2nd ed 3) Electrical Engineering Principles and Applications Allan R.Hambley ---2nd ed 4) 电路分析基础 李瀚荪 第三版 5) 电路 邱关源 第四版 6) Electric Circuits Joseph Edminister, Mahmood Nahvi -----3rd ed Basic Theory of Circuits, SJTU

  12. Chapter 1 Fundamental Knowledge Basic Theory of Circuits, SJTU

  13. What is covered in Chapter 1: • Circuit and Circuit model • Circuit Variables • Circuit Elements Basic Theory of Circuits, SJTU

  14. Circuit and Circuit Model • Actual electrical component: a battery or a light bulb • Ideal circuit component: a mathematical model of an actual electric component. Circuit Model Emphasize the main character Ideal circuit component Actual electrical component Neglect the left characters Basic Theory of Circuits, SJTU

  15. Circuit model: A commonly used mathematical model for electric system. Basic Theory of Circuits, SJTU

  16. Lumped circuit Lumped element i1 i2 Actual scale of the circuit is much smaller than the wavelength relating to the running frequency of the circuit. + V - i1=i2 ; V is certain • Linear----Nonlinear • Time invariant----Time variant • Passive----Active • Lumped----Distributive Circuit Type: Basic Theory of Circuits, SJTU

  17. dq = i dt Circuit Variables nElectric current is the time rate of change of charge, measured in amperes (A). Where q is charge in coulombs(C) A direct current (DC) is a current that remains constant with time. (I) Sort An alternating current (AC) is a current that varies sinusoidally with time. Basic Theory of Circuits, SJTU

  18. Reference direction i >0 means the real direction is same to the reference direction i i <0 means the real direction is opposite to the reference direction Basic Theory of Circuits, SJTU

  19. dw = v dq + V - Circuit Variables Voltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts(V). Where w is energy in joules(J) And q is charge in coulombs(C) Reference direction or voltage polarity V>0 means the real polarity is same to the reference polarity V<0 means the real polarity is opposite to the reference polarity Basic Theory of Circuits, SJTU

  20. passive sign convention Passive sign convention is satisfied when current enters through the positive polarity of the voltage. i + V - Unless stated, we will follow the passive sign convention throughout this course. Basic Theory of Circuits, SJTU

  21. dw = p dt \ = p vi Circuit Variables Power is the time rate of expending or absorbing energy. Measured in watts(W) using passive sign convention P=VI in a DC circuit The algebraic sum of power in a circuit, at any instant of time, must be zero. Power absorbed = - Power supplied Basic Theory of Circuits, SJTU

  22. å = p 0 Reference polaritiesfor power using passive sign convention P > 0 absorbing power P < 0 releasing or supplying power Examples Law of conservation of energy must be obeyed in any electric circuit. Power absorbed = - Power supplied Basic Theory of Circuits, SJTU

  23. t t ò ò = = w pdt vidt t t 0 0 Energyis the capacity to do work, measured in joules(J) The energy absorbed or supplied by an element from time t0 to time t is Basic Theory of Circuits, SJTU

  24. Passive elements:resistors, capacitors, and inductors Active elements:source, operational amplifiers Circuit Elements Basic Theory of Circuits, SJTU

  25. independent sources dependent sources Voltage and Current Sources An ideal independent source is an active element that provides a specified voltage or current that is completely independent of other circuit variables. Symbols for independent current source Symbols for independent voltage source The voltage is determined by itself but the current through it is determined by the outside circuit Basic Theory of Circuits, SJTU

  26. Note: • 2 or more voltage sources with different value are not permissible to be connected in parallel • 2 or more current sources with different value are not permissible to be connected in series • Voltage sources connected in series is equivalent to one voltage source • Current sources connected in parallel is equivalent to one current source • A voltage source connected to any branch in parallel is equivalent to itself • A current source connected to any branch in series is equivalent to itself Basic Theory of Circuits, SJTU

  27. An ideal dependent (or controlled) source is an active element in which the source quantity is controlled by another voltage or current. Symbols for a) dependent voltage sources b) dependent current sources There are a total of four variations 1.      A voltage –controlled voltage source (VCVS) 2.         A current –controlled voltage source (CCVS) 3.         A voltage –controlled current source (VCCS) 4.         A current –controlled current source (CCCS) Basic Theory of Circuits, SJTU

  28. I1  I1 V1 V1 VCVS CCVS I1 g V1 V1  I1 VCCS CCCS • What is the difference between independent and dependent sources? Basic Theory of Circuits, SJTU

  29. R1 1k Resistors The circuit element used to model the current –resisting behavior of a material is the resistor. Resistanceis the capacity of materials to impede the flow of current. The resistance R of an element denotes its ability to resist the flow of electric current; it is measured in ohms (Ω) Symbol: Basic Theory of Circuits, SJTU

  30. u u u t2 t1 i i i u u u t2 t1 i i i The i-v characteristic Linear Time Invariant Open Circuit Linear Time variant Short Circuit Nonlinear Time Invariant Nonlinear Time Variant Basic Theory of Circuits, SJTU

  31. v i Linear Resistor: The resistance of the idea resistor is constant and its value does not vary over time. The relation between voltage and current. (VAR) V=Ri (passive sign convention) -------Ohm’s Law Since the value of R can range from zero to infinity, it is important that we consider the two extreme possible value of R: R=0-------is called a short circuit; V=0; R=∞------is called an open circuit, I=0; Basic Theory of Circuits, SJTU

  32. 1 = G R 2 v = = = 2 p vi i R R 2 i = = = 2 p vi v G G Conductance G is the reciprocal of the resistance, measured in siemens (s) Power : P=vi (passive sign convention) always absorbs power from the circuit Other methods of expressing : About nonlinear resistor ( diode, triode) Basic Theory of Circuits, SJTU

  33. Thank you Basic Theory of Circuits, SJTU

  34. University of Sydney Basic Theory of Circuits, SJTU

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