Unit 1 Physics Foundation, Circuit Elements, KVL & KCL Unit 2 Analysis Techniques Unit 3 Op Amps & Two-Ports

Transcription

1 Unit 1 Physics Foundation, Circuit Elements, KVL & KCL Unit 2 Analysis Techniques Unit 3 Op Amps & Two-Ports

2 ROSE-HULMAN INSTITUTE OF TECHNOLOGY ECE 203 DC Circuits Winter Course Information and Syllabus Description: ECE 203 DC Circuits 3R 3L 4C F, W, S Prerequisite: MA 111 and PH 112 Definition of voltage, current, energy and power. Ohm s Law. Non ideal voltage and current sources. Measurement of voltage, current and resistance. Kirchhoff s Laws. Circuit simplification by series and parallel reduction. Thevenin, Norton and Maximum Power Theorems. Superposition Theorem. Mesh and Nodal Analysis. Two Port Circuits. Operational Amplifiers. Integral laboratory. You must get a C or better in ECE 203 to take ECE 204 AC Circuits Instructor: Dr. Carlotta A. Berry Moench, D berry123@rose hulman.edu Textbook: J.W. Nilsson & S.A. Riedel, Electric Circuits, 8 th edition, Prentice Hall, What is expected of You: First and foremost, professional work is the norm in this course. All of your written work and your conduct in class are to be at the level of one who is studying a profession the profession of engineering. This means a number of things: Grading: 1. Your work is neatly done in a professional manner, using formats specified. 2. Your work is honestly done. You are encouraged to discuss course material with classmates to help each other understand and assimilate the concepts. Nevertheless, distinguish between helping someone understand concepts and providing them with specific answers. You are expected to work individually on homework without reference to others work. 3. Your work is done on time. As a rule of thumb, expect to put in eight hours per week outside of class doing homework, reading the text, and studying. 4. You are attentive and engaged in the lecture (i.e. not sleeping, reading the newspaper, surfing the web, doing homework for other courses, disturbing others with electronics). Grades will be assigned at the end of the quarter based on the grade weights and grading scale shown below: Midterm Test I 12% A Midterm Test II 12% B Midterm Test III 12% B Final Exam 24% C Homework 10% C Laboratory assignments 15% D Lab Practical Tests 10% D Quizzes 5% F Below 60 Page 1 of 3

3 ECE 203 DC Circuits Winter Independent of point totals: You must satisfactorily complete each of the eight lab projects in order to receive a passing grade in the course Examinations: In this course, examinations make up 70% of the grade and warrant careful preparation. Examination questions will be based on the lecture material, textbook, homework, and laboratory work. The three midterm tests will be fifty minutes in duration during the regular class meeting time. Midterms and final examinations will be closed book and closed notes. You will be provided with an excerpt from the NCEES FE Reference handbook that includes some formulas. It is your responsibility to memorize or derive any formula missing from this document. Quizzes: There will be weekly quizzes that involve solving short problems or answering questions on required reading. The purposes for these quizzes are: to give me feedback on the current level of understanding of the class to give you feedback on your current level of understanding to give you practice on problems similar to the exam format to encourage collaborative learning in the classroom to also take attendance Homework: The homework is intended to help you to understand the concepts presented in the course, and to provide you with practice in problem solving. Problem sets are due each Thursday in class before the bell rings at the beginning of class. Answers and solutions will be distributed using ANGEL. Homework turned in after the bell rings is late and will incur a 20% penalty. Homework turned in after 5 pm on the due date will not be accepted. Arrange to turn in homework early if you will be away for job interviews, athletic events, etc. The required format is described in the document on Angel and in the ECE Department s guidelines and standards for writing assignments. It is your responsibility to make your methods and results clear to the grader. 1.rose hulman.edu/ece/images/stories/files/ecewritingstandards.pdf Laboratory Supplies: Each student team must purchase an ECE203 kit with breadboard from the parts room before the first lab. Each individual student is required to purchase a laboratory notebook (10 x7 7/8, 80 sheets, 5x5 Quad Ruled, #26 251, available at the bookstore). The format for notebook entries can be found under the ECE Department s guidelines and standards for writing assignments. Additional specifications are provided in the ECE203 DC Circuits Laboratory Manual CAB Page 2 of 3

4 ECE 203 DC Circuits Winter Prelabs: Prelab exercises are due the day before lab at the beginning of class before the bell rings. Each student should do the pre lab in their lab notebook and make a photocopy to turn in. The solutions to the prelab may be presented at the start of the lab period. Any student that has not completed the prelab must do it at the beginning of lab for zero credit. This team must still finish the laboratory project within the allotted time. Laboratory Notebooks: Laboratory notebooks will be collected at the conclusion of each laboratory period. The laboratory notebook will be graded and both members of the team share the notebook grade. Each team member must alternate submission of the lab notebook as well as circuit building on a weekly basis. Re grades: All requests for re grades must be made in writing within one week of the return of the assignment or exam. The student should not make any marks on the document and must attach a memorandum that details a technical justification for the reason for the submission. It should be noted that based upon the request, the grade may increase, decrease or remain the same. Attendance: Regardless of whether formal attendance is taken, attendance at each class is expected. As a rule of thumb you should consider yourself seriously behind if you miss more than four classes in a four credit hour course. According to our Academic Rules and Procedures, A student whose total absences in a course, excused or unexcused, exceed two per credit is liable to fail the course. Eight absences in this course are grounds for failure. Missing an attendance check due to lateness may be counted as an absence. If you miss a lab with an excused absence you need to make it up within 1 week without penalty. If you miss a lab without an excused absence, you need to make it up within 1 week and you will receive a grade of zero. If you come to lab more than 15 minutes late you need to complete the lab on your own. Missed exams will not be made up. The final exam grade will be used to replace a missing test grade in the case of excused absences. An excused absence from an examination normally requires advance approval or formal documentation of an emergency. An examination that is missed for an unexcused reason will be given a grade of zero. Students are not excused from scheduled exams for intramural athletics or fraternity events. Calculators & Computers: You will need a calculator that can perform arithmetic with complex numbers (TI 83 plus or better). You are encouraged to practice doing the homework with the same calculator you will use on the exam. It is important to learn to do simultaneous equations (or matrix) calculations with your calculator to be successful in this course. Maple can be used on the homework problems, but not in the exams. Academic accommodation: Those students with documented special needs may request extra time on timed tests. Students need to contact me at least 2 business days prior to each exam to make the necessary arrangements. CAB Page 3 of 3

5 ROSE HULMAN INSTITUTE OF TECHNOLOGY WEDNESDAY LAB ECE 203 DC Circuits Winter Course Calendar Class Day Date Topic Reading Due 1 1 M 11/30 Syllabus, Introduction, Circuit Analysis Overview T 12/1 Voltage, current, power, energy, passive sign convention Prelab 1 1 L W 12/2 Lab 1. Introduction to Laboratory Techniques 1 3 R 12/3 Sources, Resistors, Ohm s Law, Power Calculations HW M 12/7 Kirchhoff s Laws Quiz 2 2 T 12/8 Kirchhoff s Laws Prelab 2 2 L W 12/9 Lab 2. Ohm s Law, KVL, and KCL 2 3 R 12/10 Resistors in parallel and series HW M 12/14 Voltage and Current Divider Quiz 3 2 T 12/15 Wheatstone Bridge and Delta Wye Equivalents Prelab 3 3 L W 12/16 Lab 3. Voltage and Current Divider HW R 12/17 Midterm Test 1 (up through Chapter 3) WINTER BREAK (12/19/09 01/03/10) 4 1 M 1/4 Node voltage method T 1/5 Node voltage method (special cases) Prelab 4 4 L W 1/6 Lab 4. Node voltage method 4 3 R 1/7 Mesh current method 4.5 HW M 1/11 Mesh current method (special cases) Quiz 5 2 T 1/12 Source Transformations 4.9 Prelab 5 5 L W 1/13 Lab 5. Mesh current method 5 3 R 1/14 Thevenin and Norton Equivalents HW M 1/18 Thevenin and Norton Equivalents Quiz 6 2 T 1/19 Maximum Power Transfer L W 1/20 Lab 6. Lab Practical Test I 6 3 R 1/21 Superposition 4.13 HW M 1/25 Introduction to Operational Amplifiers Quiz 7 2 T 1/26 Midterm Test 2 (up through Chapter 4 section 12) 7 L W 1/27 Lab 7. Source Transformations, Thevenin and Norton Equivalents Prelab R 1/28 Inverting and summing op amps HW M 2/1 Noninverting, difference, cascaded op amps Quiz 8 2 T 2/2 More realistic op amps 5.7 Prelab 8 8 L W 2/3 Lab 8. Operational Amplifiers 8 3 R 2/4 Operational amplifier applications HW M 2/8 Terminal equations, two port parameters Quiz 9 2 T 2/9 Midterm Test 3 (up through Chapter 5) Prelab 9 9 L W 2/10 Lab 9. Inverting and Noninverting Op Amps 9 3 R 2/11 Two port parameters 18.2 HW M 2/15 Terminated two port circuits 18.3 Quiz 10 2 T 2/16 Cascaded two port networks L W 2/17 Lab 10. Lab Practical Test II 10 3 R 2/18 Final Review, Course Evaluations HW 10 CAB Rev. 10/15/09

6 ROSE HULMAN INSTITUTE OF TECHNOLOGY FRIDAY LAB ECE 203 DC Circuits Winter Course Calendar Class Day Date Topic Reading Due 1 1 M 11/30 Syllabus, Introduction, Circuit Analysis Overview T 12/1 Voltage, current, power, energy, passive sign convention R 12/3 Sources, Resistors, Ohm s Law, Power Calculations HW 1, Prelab 1 1 L F 12/4 Lab 1. Introduction to Laboratory Techniques 2 1 M 12/7 Kirchhoff s Voltage and Current Laws Quiz 2 2 T 12/8 Kirchhoff s Voltage and Current Laws R 12/10 Resistors in parallel and series HW 2, Prelab 2 2 L F 12/11 Lab 2. Ohm s Law, KVL, and KCL 3 1 M 12/14 Voltage and Current Divider Quiz 3 2 T 12/15 Wheatstone Bridge and Delta Wye Equivalents /16 HW R 12/17 Midterm Test 1 (up through Chapter 3) 3 L F 12/18 Lab 3. Voltage and Current Divider Prelab 3 WINTER BREAK (12/19/09 01/03/10) 4 1 M 1/4 Node voltage method T 1/5 Node voltage method (special cases) R 1/7 Mesh current method 4.5 HW 4, Prelab 4 4 L F 1/8 Lab 4. Node voltage method 5 1 M 1/11 Mesh current method (special cases) Quiz 5 2 T 1/12 Source Transformations R 1/14 Thevenin and Norton Equivalents HW 5, Prelab 5 5 L F 1/15 Lab 5. Mesh current method 6 1 M 1/18 Thevenin and Norton Equivalents Quiz 6 2 T 1/19 Maximum Power Transfer R 1/21 Superposition 4.13 HW 6 6 L F 1/22 Lab 6. Lab Practical Test I 7 1 M 1/25 Introduction to Operational Amplifiers Quiz 7 2 T 1/26 Midterm Test 2 (up through Chapter 4) 7 3 R 1/28 Inverting and summing op amps HW 7, Prelab 7 7 L F 1/29 Lab 7. Source Transformations, Thevenin and Norton Equivalents 8 1 M 2/1 Noninverting, difference, cascaded op amps Quiz 8 2 T 2/2 More realistic op amps R 2/4 Operational amplifier applications HW 8, Prelab 8 8 L W 2/5 Lab 8. Operational Amplifiers 9 1 M 2/8 Terminal equations, two port parameters Quiz 9 2 T 2/9 Midterm Test 3 (up through Chapter 5) 9 3 R 2/11 Two port parameters 18.2 HW 9, Prelab 9 9 L W 2/12 Lab 9. Inverting and Noninverting Op Amps 10 1 M 2/15 Terminated two port circuits 18.3 Quiz 10 2 T 2/16 Cascaded two port networks R 2/18 Final Review, Course Evaluations HW L F 2/19 Lab 10. Lab Practical Test II CAB Rev. 10/18/09

7 ROSE HULMAN INSTITUTE OF TECHNOLOGY ECE 203 DC Circuits Winter Assigned Homework Problems Homework Problems Due HW1 Chapter 1 1.1, 1.9, 1.15, 1.30 P1 The following figure shows the power consumption of a certain household in one day. Calculate: a. The total energy consumed in kwh b. The average power per hour 12/3/09 HW2 Chapter , 2.11, 2.18, 2.29 P2 Find R for the following circuit 12/10/09 HW3 Chapter 3 3.5, 3.10, 3.14, 3.52 P3 For the following Wheatstone bridge circuit, a. R is a 10 kω variable resistor, what is the range of V ab? b. For what value of R is the bridge balanced? c. If a 5 kω resistor is placed between terminals a and b, and R = 7.5 kω, what is the current through the 5 kω resistor? 12/16/09 CAB Rev. 10/15/09

8 HW4 Section , 4.11, 4.17, 4.26 P4 Use the node voltage method to determine the gain, v o /v s for the following transistor amplifier circuit. 1/7/10 HW5 Section , 4.37, 4.47, 4.59 P5 The following circuit models a common emitter transistor amplifier. Find i x using source transformation. 1/14/10 HW6 Section , 4.66, 4.69, 4.77 P6 The Thevenin equivalent terminals a b of the linear network shown in the following figure can be determined by measurement. When a 10 kω resistor is connected to terminals a b, the voltage V ab is measured as 6 V. When a 30 kω resistor is connected to the terminals, V ab is measured as 12 V. Determine: a. The Thevenin equivalent at terminals a b b. V ab when a 20 kω resistor is connected across terminals a b 1/21/10 2

9 HW7 Section , 4.85, 4.90, 4.97 P7 For the following circuit, determine the value of R such that the maximum power delivered to the load is 5 mw. 1/28/10 HW8 Chapter 5 5.3, 5.11, 5.15, 5.28 P8 In the following op amp circuit, determine the current i o. 2/4/10 HW9 HW10 Two Port Parameters 18.4, 18.8, 18.9, 18.11, Terminated and Cascaded Two Port Networks 18.36, 18.37, , P10 For the following two port circuit, if the h parameters are h 11 = 16 Ω, h 12 = 3, h 21 = 2, h 22 = 0.01 S, find the power delivered to the 25Ω resistor. I V V 10 V Ω _ 2/10/10 2/18/10 3

10 have components with 2 terminals that can be described in terms of current and/or voltage which are IDEAL CIRCUIT ELEMENTS drawn such that current flows from the positive terminal (charge) to negative terminal (charge) obeys the PASSIVE SIGN CONVENTION Introduction ELECTRICAL SYSTEMS Have positive and negative Have capacity to do work CHARGE, q (C) ENERGY, w (J) Can be neither created nor destroyed only transferred LAW OF CONSERVATION OF ENERGY Flow yields Separation yields Per unit charge Rate with respect to time CURRENT, i (A) VOLTAGE, v (V) POWER, p (W) Flows from the (-) ve terminal to a (+)ve terminal Flows from the (+) ve terminal to a (-)ve terminal P = VI < 0 P = VI > 0 VOLTAGE RISE VOLTAGE DROP POWER DELIVERED POWER ABSORBED ECE203 DC Circuits - C.A. BERRY 11/15/09

11 RESISTORS Impede the flow of current V = ir PASSIVE CIRCUIT ELEMENTS Model a device that cannot generate electric energy INDUCTORS Store magnetic flux and induces voltage related to current v = L di/dt CAPACITORS store electric charge and produce a current based upon electric field i = C dv/dt IDEAL CIRCUIT ELEMENTS establishes voltage and current in a circuit without relying on voltage and current elsewhere in the circuit is an INDEPENDENT SOURCE produces a constant current in a circuit IDEAL CURRENT SOURCE ACTIVE CIRCUIT ELEMENTS Model a device capable of generating electric energy ELECTRIC SOURCES Convert non-electric energy to electric energy produces a constant voltage in a circuit IDEAL VOLTAGE SOURCE establishes voltage and current in a circuit which depends on voltage and current elsewhere in the circuit is a DEPENDENT SOURCE CURRENT-CONTROLLED CURRENT SOURCE VOLTAGE-CONTROLLED VOLTAGE SOURCE VOLTAGE-CONTROLLED CURRENT SOURCE CURENT-CONTROLLED VOLTAGE SOURCE ECE203 DC Circuits - C.A. BERRY 11/15/09 Produces a current based upon current elsewhere in the circuit Produces a voltage based upon voltage elsewhere in the circuit Produces a voltage based upon current elsewhere in the circuit Produces a current based upon a voltage elsewhere in the circuit

12 ELECTRICAL SYSTEMS with sources that produce current or voltage that is constant with time are DC CIRCUITS can be analyzed using can be simplified by OHM S LAW SUPERPOSITION LAW OF CONSERVATION OF ENERGY SOURCE TRANSFORMATIONS COMBINING RESISTORS ONE PORT CIRCUITS states that current into a node equals current out of a node is states that voltage rises equal voltage rises around a loop is in THEVENIN/NORTON THEOREMS KIRCHHOFF S CURRENT LAW is used to apply KIRCHHOFF S VOLTAGE LAW is used to apply in using MAXIMUM POWER TRANSFER NODE-VOLTAGE METHOD CURRENT DIVIDER MESH-CURRENT METHOD VOLTAGE DIVIDER PARALLEL SERIES WYE DELTA TRANSFORMATIONS ECE203 DC Circuits - C.A. BERRY 11/15/09

13 Active Circuit Elements that behave like voltage controlled voltage sources and can perform math operations are Operational Amplifiers More realistic model Ideal op-amps have 2 constraints or assumptions Virtual short condition Infinite input impedance condition Op-amps are analyzed using the 2 assumptions and KCL Can be used to find the voltage characteristics for several types of op-amps Inverting Non-inverting Summing Difference ECE203 DC Circuits - C.A. BERRY 11/1/09

14 DC CIRCUITS Can be described by the voltage and current characteristics at their PORTS Has an output port described by the Signals can be fed into or extracted from either ONE PORT TWO PORT CIRCUITS Described by the THEVENIN/NORTON EQUIVALENT Have separate ports for input and output described by PARAMETERS (z, b, a, h, y, g) Driven at one port and loaded at the other port are TERMINATED Two port circuits with two port circuits as inputs our outputs are CASCADED ECE203 DC Circuits - C.A. BERRY 11/15/09

15 Voltage, Current Power, Energy Passive sign convention Sources Resistors, Ohm s Law Kirchhoff s Voltage Law Kirchhoff s Current Law Resistors in series and parallel Voltage and Current Divider Wheatstone Bridge Delta-Wye Equivalents

16 Lecture 1 1 Circuit Analysis Overview Reading: Objectives: Be able to able to briefly and clearly explain static electricity and electrical circuit Be able to use SI units and the standard prefixes for power of 10 ************************************** An electric circuit is a mathematic model that approximates the behavior of an actual electric system. A commonly used mathematical model for electric systems is a circuit model. The elements that comprise the circuit model are called ideal circuit components. Circuit analysis is the tools applied to an electric circuit using mathematical techniques to predict the behavior of the circuit model and its ideal circuit components. The physical prototype is an actual electric system, constructed from actual electric components. In Class Activity: Watch the video from Jimmy Kimmel Live. What is the source? What is the resistance? What is the switch? Why do you think that Jimmy had to jump in the air in order to shock the people? C.A. Berry Lec1 1.docx Page 1 of 2

17 DC Circuit Water Analogy It is possible to understand a simple DC circuit by relating it to a water circuit. Pressure, P drives water around the closed loop pipe Voltage, V drives the charge around the closed at a certain volume flowrate, F circuit at a certain electric current, I A pump takes water at a low pressure and does work A battery takes in charge at a lower voltage, on it to eject it at a higher pressure does work on it and ejects it at a higher voltage Constriction of the pipe represents resistance to Resistance to electric current causes a voltage water flow and causes a pressure drop drop The reservoir supplies water to the pipe and is a The ground supplies charge to the circuit and pressure reference holds a reference voltage A large pipe has very little resistance to flow A wire has very little resistance to charge flow astr.gsu.edu/hbase/electric/watcir.html Review the International System of Units and Standardized prefixes for powers of 10. C.A. Berry Lec1 1.docx Page 2 of 2

18 Lecture 1 2 Voltage, current, power, energy, passive sign convention Reading: Objectives: Be able to briefly and clearly explain voltage, current, power, energy Be able to write formulas for voltage, current, power Be able to identify whether an element is delivering or absorbing power Be able to explain the difference between power and energy Be able to apply the law of conservation of energy to confirm that power balances for a network Be able to use the passive sign convention to calculate the power for an ideal basic circuit element given its voltage and current ************************************** The separation of electric charge creates an electric force (voltage). Whenever positive and negative charges are separated, energy is expended. Voltage is the energy per unit charge created by this separation. dw v = dq v is voltage in volts (V), w is energy in Joules (J), q is charge in Coulombs (C) The motion of charge creates an electric fluid (current). The rate of charge flow is known as electric current. dq i = dt i is current in amperes (A), q is charge in Coulombs (C), t is time in seconds (s) In Class Activity The current flowing into the positive terminal of an element is given by the following waveform. If the element is initially charged to 2 C, what is the total charge transferred to the element in 5 seconds? i(t), 4 A time, s C.A. Berry Lec1 2.docx Page 1 of 3

19 An ideal basic circuit element has 3 attributes: (1) it has only 2 terminals, (2) it is described mathematically in terms of current and/or voltage, (3) it cannot be subdivided into other elements. + v - i A voltage drop is when current flows through an element from the positive to negative terminal on an element, otherwise it is a voltage rise. The passive sign convention states that when the direction of current flow through an element is in the direction of the voltage drop across the element, use a positive sign that relates the voltage to the current, otherwise use a negative sign. Concept Question: The charge flowing through a light bulb is shown in the figure on the right. Which of the following figures shows the current flowing through the light bulb? a) I b) II c) III d) none of the above q, C time, s i, A I II III i, A i, A ************************************************************************ The useful output of electrically based systems often is non electrical. This output is expressed in terms of power or energy. Power is the time rate of expending or absorbing energy. dw p = dt p is the power in Watts (W), w is the energy in Joules (J), t is the time in seconds (s) The power associated with the flow or charge follows directly from the definition of voltage and current dw dw dq p = =. = vi dt dq dt p is the power in Watts (W), v is the voltage in volts (V), i is the current in amperes (A) C.A. Berry Lec1 2.docx Page 2 of 3

20 If the current flowing through an element is in the direction of the voltage drop across the element, p = + vi, otherwise it is p = vi. If the numerical value of power is positive (p > 0), the element is absorbing power, otherwise the element is delivering power. The law of conservation of energy states that energy can neither be created nor destroyed only transferred. Therefore, the total power delivered to an electric circuit must be equal to the total power absorbed. In Class Activity: Figure 1 and 2 shows the current through and the voltage across a device. Sketch the power and find the total energy absorbed by the device for the period of 0<t<8 ms. i, ma Figure time, ms v, V Figure time, ms p, W time, ms In Class Activity: In the following circuit, a) identify which elements are drawn to obey the passive sign convention, b) using the numerical values on the table, identify which elements are absorbing power and which are delivering power, c) confirm that the law of conservation of energy is satisfied. element Voltage (V) Current (A) a 8 4 b c d e f v d _ i d d i b b + v a - a + v b - + v c - - v e + i e e i a c + v f _ i c f i f C.A. Berry Lec1 2.docx Page 3 of 3

21 Lecture 1 3 Sources, resistors, Ohm s law, Power Calculations Reading: Objectives: Be able to explain Ohm s law, power across a resistor, ideal voltage and current sources, active and passive circuit elements Be able to identify resistors in a network Be able to solve for voltage, current and power in a resistive network Be able to apply the law of conservation of energy to a resistive circuit ************************************** An electric source is a device that is capable of converting nonelectric energy to electric energy and vice versa. These sources can either absorb power or deliver power, generally by maintaining either voltage or current. Independent sources establish a voltage or current in a circuit without relying on voltage or currents elsewhere in the circuit. Dependent sources or controlled sources establish a voltage or current in a circuit whose value depends on the value of a voltage or current elsewhere in the circuit. Dependent sources are used to model transistors and operational amplifiers. Element Description Graphic Independent Establishes a voltage or current in a circuit Sources without relying on voltages and currents elsewhere in the circuit ideal current source This circuit symbol is a circle and must include an arrow for the direction of the current and a ideal voltage source Dependent or Controlled Sources current controlled current source (CCCS) voltage controlled voltage source (VCVS) value. This circuit symbol is a circle and must include a polarity for the reference voltage and a value Establishes a voltage or current in a circuit which depends on a voltage or current elsewhere in the circuit. This circuit symbol is a diamond and it must include an arrow for the direction of the supplied current, a formula to calculate the supplied current from the controlling current, i x. i s = βi x (β is unit less) This circuit symbol is a diamond and it must include a reference polarity for the supplied voltage, a formula to calculate the supplied voltage from the controlling voltage, v x. v s = μv x (μ is unit less) + _ + _ i s v s βi x μv x C.A. Berry Lec1 3.docx Page 1 of 3

22 voltage controlled This circuit symbol is a diamond and it must current source include an arrow for the direction of the (VCCS) supplied current, a formula to calculate the αv x supplied current from the controlling voltage, v x. current controlled voltage source (CCVS) i s = αv x (α s units are A/V) This circuit symbol is a diamond and it must include a reference polarity for the supplied voltage, a formula to calculate the supplied voltage from the controlling current, i x. v s = ρi x (ρ s units are V/A) + _ ρi x An active circuit element is one that models a device capable of generating electric energy A passive circuit element models physical devices that cannot generate electric energy. Resistors, Inductors, and Capacitors are examples of passive circuit elements. In Class Activity What value of v s is required in order for the following interconnection to be valid? In Class Activity What value of α is required in order for the interconnection to be valid? Resistance, R is the capacity of materials to impede the flow of current or the flow of electric charge. The circuit element used to model this behavior is the resistor. Many useful devices take advantage of resistance heating including stoves, toasters, irons, and space heaters. C.A. Berry Lec1 3.docx Page 2 of 3

23 Ohm s law describes the voltage across a resistor, v = ir, where v is the voltage in volts, i is the current in amperes, and R is the resistance in ohms (Ω) The reciprocal of resistance is conductance, G measured in Siemens (S) or mhos. G = 1/R (S) The power dissipated in a resistor is given by the following formulas p = i 2 R = v 2 /R = v 2 G = i 2 /G (W) FE Preview: A 5 Ω resistor is placed in series with a varying current. Most nearly how much energy is dissipated by the resistor over the 4 s time interval shown? i(t), Amperes time, seconds a) 80 J b) 180 J c) 200 J d) 320 J In Class Activity For the following circuit, confirm that it satisfies the law of conservation of energy. In Class Activity For the following circuit, confirm that it satisfies the law of conservation of energy. C.A. Berry Lec1 3.docx Page 3 of 3

24 Lecture 2 1 Kirchhoff s Voltage and Current Laws Reading: Objectives: Be able to briefly and clearly explain Kirchhoff s voltage and current laws Be able to solve circuits for voltage, current, and power using KCL and KVL ************************************** A node is a point where two or more circuit elements meet. Kirchhoff s current law (KCL ) states that the algebraic sum of all the currents at any node in a circuit equals zero. (i.e. current in = current out) i 1 i 2 + i 3 + i 4 i 5 = 0 i 1 + i 3 + i 4 = i 2 + i 5 A closed loop or path in a circuit is any closed path in a circuit through selected basic circuit elements and return to the original node with passing any intermediate node more than once. Kirchhoff s voltage law states that the algebraic sum of the voltages around any closed path in a circuit equals zero. (i.e. voltage drops = voltage rises) v 1 + v 4 = v 2 + v 3 + v 5 v 1 + v 2 +v 3 v 4 +v 5 = 0 Write 3 KCL and 3 KVL equations for the following circuit. C.A. Berry Lec2 1.docx Page 1 of 4

25 In Class Activity 1: Use KCL, to find all of the voltages and current in the following circuit. Finally, confirm that the circuit satisfies the law of conservation of energy. element V, V I, A P del, W P abs, W 5A 10A 2 Ω 6 Ω TOTAL C.A. Berry Lec2 1.docx Page 2 of 4

26 In Class Activity 2: Use KVL, to find all of the voltages and current in the following circuit. Finally, confirm that the circuit satisfies the law of conservation of energy. element V, V I, A P del, W P abs, W 12 V 6 V 2 Ω 4 Ω 12 Ω TOTAL C.A. Berry Lec2 1.docx Page 3 of 4

27 In Class Activity 3: Use KVL to find v 1 and v 2. C.A. Berry Lec2 1.docx Page 4 of 4

28 Lecture 2 2 Kirchhoff s Voltage and Current Laws Reading: Objectives: Be able to briefly and clearly explain Kirchhoff s voltage and current laws Be able to solve circuits for voltage, current, and power using KCL and KVL Recall that ************************************** KVL states that = 0 (i.e. voltage rises = voltage drops) KCL states that = 0 (i.e. current in = current out) In Class Activity 1: For the following circuit, find i o and v o. Confirm that the circuit obeys the law of conservation of energy. element V, V I, A P del, W P abs, W 6 A i o /4 8 Ω 2 Ω TOTAL C.A. Berry Lec2 2.docx Page 1 of 4

29 In Class Activity 2: For the following circuit, find i o. C.A. Berry Lec2 2.docx Page 2 of 4

30 In Class Activity 3: For the following circuit, find v x and v o. Confirm that the circuit obeys the law of conservation of energy. element V, V I, A P del, W P abs, W 35 V 2 v x 10 Ω 5 Ω TOTAL C.A. Berry Lec2 2.docx Page 3 of 4

31 In Class Activity 4: For the following circuit, use KVL and KCL to find a) i 1, i 2, i 3 b) v 1, v 2, v 3 C.A. Berry Lec2 2.docx Page 4 of 4

32 Lecture 2 3 Resistors in parallel and series Reading: Objectives: Be able to recognize resistors connected in series and in parallel and use the rules of combining resistors to yield equivalent resistance ************************************** When two elements connect at a single node, they are said to be in series. Elements in series have the same current. The equivalent resistance for resistors in series is the sum of the individual resistors. Therefore the equivalent resistance is always larger than the largest individual resistor. R eq = R 1 + R R n When two elements connect at a single node pair, they are said to be in parallel. Elements in parallel have the same voltage. The equivalent resistance is reciprocal of the sum of the individual conductances. Therefore the equivalent resistance is always smaller than the smallest individual resistor R eq = + + L + R R R 1 2 n G eq = G 1 + G G n The special case for 2 parallel resistors is the product over the sum, R eq = (R 1 R 2 )/(R 1 + R 2 ) 1 C.A. Berry Lec2 3.docx Page 1 of 4

33 Concept Question: In the following circuit, a 75 W and 50 W bulb are placed in parallel across a voltage source, which of the following statements is true 75-W a) the current through the 50 W bulb is larger b) the current through the 75 W bulb is larger c) the current through both bulbs is the same 50-W d) none of the above Concept Question: In the following figure, as more identical resistors are added to the parallel circuit between points P and Q, the total resistance between points P and Q a) increases b) decreases c) remains the same d) none of the above In Class Activity 1: For the following circuit, a) Find R ab b) If a 10V source is placed across terminals a and b, what the is the power delivered by the source? C.A. Berry Lec2 3.docx Page 2 of 4

34 ECE203 DC Circuits Winter 2009/2010 In Class Activity 2: For the following circuit, a) Find R ab b) If a 10mA source is placed across terminals a and b, what is the current through each of the 2 kω resistors? C.A. Berry Lec2 3.docx Page 3 of 4

35 In Class Activity 3: For the following circuit, a) Find R ab b) If a 25 V source is placed across terminals a and b, what is the voltage, V db? C.A. Berry Lec2 3.docx Page 4 of 4

36 Lecture 3 1 Voltage and Current Divider Reading: Objectives: Be able to design simple voltage divider and current divider circuits Be able to apply current and voltage division to solve simple circuits Be able to derive the voltage divider using KVL Be able to derive the current divider using KCL ************************************** The voltage divider is used to calculate the voltage across several resistors when the voltage is supplied from a single source. In order to use the voltage divider, all of the elements must be in series. Use KVL to find the voltage across R 3 : v + v 1 + v 2 + v 3 = 0 Use Ohm s law to rewrite voltages across the resistors: v + ir 1 + ir 2 + ir 3 = 0 Solve for the current through the resistors: i = v/ (R 1 + R 2 + R 3 ) Use Ohm s law to find v 3 : v 3 = ir 3 = vr 3 /(R 1 + R 2 + R 3 ) Therefore the voltage divider rule is v n = Rn R v x x The current divider is used to calculate the current through several resistors when the current is supplied from a single source. In order to use the current divider rule, all of the elements must be in parallel. Use KCL to find the current through R 3 : i + i 1 + i 2 + i 3 = 0 Use Ohm s law to rewrite the currents across the resistors: i + v/r 1 + v/r 2 + v/r 3 = 0 Solve for the voltage across the resistors: v = i[1/r 1 + 1/R 2 +1/ R 3 ] 1 = i/(g 1 + G 2 + G 3 ) Use Ohm s law to find i 3 : i 3 = v/r 3 = vg 3 = ig 3 /(G 1 + G 2 + G 3 ) = = i[1/r 1 + 1/R 2 +1/ R 3 ] 1 / R 3 G R n eq Therefore the current divider rule is i n = i = i G + G + LG R 1 2 n n C.A. Berry Lec3 1.docx Page 1 of 4

37 In Class Activity 1: For the following circuit, a) use the voltage to find v 1 and v 2 b) use the current divider to find i 1 and i 2 C.A. Berry Lec3 1.docx Page 2 of 4

38 In Class Activity 2: For the following circuit, a) use the current divider to find i 1, i 2 and v 2 b) use the voltage to find v 1 C.A. Berry Lec3 1.docx Page 3 of 4

39 In Class Activity 3: For the above circuit, a) Write a voltage divider relationship between the 10V source and V a, V b, and V c. b) Use the voltage divider to find V a, V b, and V c. In Class Activity 4: For the above circuit, a) Write a current divider relationship between I a, I b, and I c b) Use the current divider to find I b and I c c) Write a current divider relationship to find I d d) Use the current divider to find I d C.A. Berry Lec3 1.docx Page 4 of 4

40 Lecture 3 2 Wheatstone Bridge and Delta Wye Equivalents Reading: Objectives: Be able to identify a Wheatstone Bridge and find the resistance to balance the bridge Be able to analyze a Wheatstone bridge to find unknown voltages and currents Be able to apply delta to Wye equivalents to solve simple circuits ************************************** The purpose of the Wheatstone Bridge is to make precise resistance measurement. One application of a Wheatstone Bridge is to place a strain gauge in one leg in order to measure small changes in resistance in the range of 1 Ω to 1 MΩ to detect the strain on a device. A detector called a galvanometer can be placed in the bridge to measure current in the μa range. The bridge is balanced when there is no current flowing through the galvanometer. In Class Activity 1: Determine what value of resistance, R x, causes the Wheatstone bridge to balance. In Class Activity 2: For the following Wheatstone bridge, determine what value of resistance, R x, causes the bridge to balance. If these are 25 mw resistors, do any of them exceed their power dissipating capacity? C.A. Berry Lec3 2.docx Page 1 of 4

41 In Class Activity 3: For the following Wheatstone bridge, determine the detector current, i d if the voltage drop across the detector is negligible. In Class Activity 4: For the following circuit, what is the bridge output voltage, v o? C.A. Berry Lec3 2.docx Page 2 of 4

42 Delta Wye Equivalents When the internal resistance of the galvanometer is modeled in the Wheatstone Bridge this creates a special configuration of resistances that is neither series nor parallel. Therefore this interconnection cannot be simplified by using series and parallel combinations. These special configurations are referred to as Delta (Δ) or Wye ( Y ) interconnections and they can be transformed to equivalent representations. Δ or π interconnection R a = R 1 = R b = R 2 = R c = R 3 = Y or T interconnection NOTE: Each resistor in the Δ network is the sum of all possible products of Y resistors taken two at a time divided by the opposite Y resistor. The Y and Δ configurations are said to be balanced when the resistance in each branch is the same and R Y = R Δ /3 or R Δ =3 R Y The following figure is a superposition of the Y and Δ configurations to aid in transforming from one to another. What does equivalent mean? Equivalent means that both configurations have the same voltage and current characteristics at the terminals a, b, and c. If these 2 networks were in a black box and you measured voltage and current, you could not state whether it was a Δ or Y interconnection in the box. However, you CANNOT state that the voltage across and current through the internal resistors is the same for both. C.A. Berry Lec3 2.docx Page 3 of 4

43 In Class Activity 5: For the following circuit, determine the equivalent resistance at terminals a and b if all of the resistors have a value of 30Ω. In Class Activity 6: For the following circuit, a) use 2 different Δ to Y transformations to find the voltage v 1. b) Use a Δ to Y transformation to find the power delivered by the 80V source. C.A. Berry Lec3 2.docx Page 4 of 4

44 Node-voltage method Mesh-current method Source Transformations Thevenin and Norton Equivalents Maximum Power Transfer Superposition

45 Lecture 4 1 Node voltage method Reading: Objectives: Be able to briefly and clearly explain in your own words node, node voltage method Be able to identify nodes in a circuit Be able to apply the node voltage method to calculate voltage, current, and power in an electric circuit ************************************** A planar circuit is a circuit that can be drawn on a plane with no crossing branches. The nodevoltage method can be used on planar and non planar circuits. However, the mesh current method cannot be used on non planar circuits (see Figures 4.1 and 4.2 on page 94 in the textbook for examples of both). All of the terms used to describe a circuit are provided in the following table. node essential node path branch a point where two or more circuit elements join a node where 3 or more circuit elements join a trace of adjoining basic elements with no elements included more than once a path that connects two nodes essential branch loop mesh a path which connects two essential nodes without passing through an essential node a path whose last node is the same as the starting node a loop that does not enclose any other loops C.A. Berry Lec4 1.docx Page 1 of 4

46 Recall that Kirchhoff s current law states that the sum of the currents in and out of a node must equal zero. The node voltage law is based upon using KCL to analyze a circuit to independent simultaneous equations to solve for node voltages. The number of equations required is based upon the branches and nodes in the circuit. If there are n nodes in a circuit, then it is possible to derive n 1 equations using KCL and b (n 1) equations using KVL. In Class Activity: How many nodes and branches are in the following circuit? How many KCL and KVL equations are required to solve for the unknown branch currents? Steps to implement the node voltage method i. make a neat layout of the circuit with no branches overlapping ii. mark one of the essential nodes the reference node (typically the one with the most branches near the bottom of the circuit) [note: this is the ground (0 V), all node voltages are with respect to this node] iii. node voltages are defined as the voltage rise from the ground node to a non reference node iv. label all of the node voltages on the circuit (v1, v2, v3, etc.) v. draw currents leaving each labeled node if it is not given vi. use Ohm s law to write the KCL equations at each of the non reference labeled nodes vii. Solve the simultaneous equations by using Cramer s rule, matrix manipulation or your calculator to find the node voltages viii. Finally complete the power table by using the derived values. C.A. Berry Lec4 1.docx Page 2 of 4

47 In Class Activity 1: For the above circuit, execute steps i v of the node voltage method. Use the node voltage method to confirm that the circuit satisfies the law of conservation of energy. element V (V) I (A) Power (W) delivered 20mA 5 ma 10 ma 2 kω 4 kω 2 kω 4 kω 1 kω TOTAL Power (W) absorbed C.A. Berry Lec4 1.docx Page 3 of 4

48 In Class Activity 2: Use the node voltage method to find the voltage across the current sources in the following circuit. C.A. Berry Lec4 1.docx Page 4 of 4

49 Lecture 4 2 Node voltage method (special cases) Reading: Objectives: Be able to apply the node voltage method to circuits with voltage sources to solve for voltage, current, and power ************************************** As seen from the prior lecture, when circuit includes dependent sources, the node voltage method must be supplemented with constraint equations imposed on the dependent source. When a voltage source is between two non reference nodes, the equation derivation is simplified because the voltage between the 2 essential nodes is constrained by the value of the source. This voltage source between two non reference nodes and any element in parallel with it is called a supernode. Properties of a supernode: 1. The voltage source inside the supernode provides a constraint equation needed to solve for the node voltages. 2. A supernode has no voltage of its own. 3. A supernode requires the application of both KCL and KVL. To analyze the supernode: 1. perform KCL into and out of the supernode, (i.e., i 4Ω + i 3Ω + i 2Ω + i 6Ω = 0) 2. perform KVL at the supernode (i.e., v 2 v 1 = 3 V) Finally, since the purpose of the node voltage method is to use KCL to find all unknown nodevoltages, it is also not necessary to perform KCL at the 7V source. Instead of labeling this node as v 1 or v 2, refer to it at 7V. C.A. Berry Lec4 2.docx Page 1 of 4

50 In Class Activity 1: For the above circuit, a) outline how you would use the node voltage method to find all of the unknown voltages b) confirm that the circuit satisfies the law of conservation of energy Element V (V) I (A) Power (W) delivered 7V 3V 4 Ω 3 Ω 4 Ω 6 Ω 2 Ω TOTAL Power (W) absorbed C.A. Berry Lec4 2.docx Page 2 of 4

51 In Class Activity 2: For the above circuit, are there any supernodes? if so, what are they? Use the node voltage method to analyze the circuit and confirm that the circuit satisfies the law of conservation of energy. Element V (V) I (A) Power (W) delivered 10 V 5 V 2 Ω 4 Ω 6 Ω 8 Ω TOTAL Power (W) absorbed C.A. Berry Lec4 2.docx Page 3 of 4

52 In Class Activity 3: For the following circuit, use the node voltage method to find v 1, v 2, v 3, v o, and I o. C.A. Berry Lec4 2.docx Page 4 of 4

53 Lecture 4 3 Mesh current method Reading: 4.5 Objectives: Be able to briefly and clearly explain in your own words loop, mesh, mesh current and mesh current method Be able to identify loops and meshes in a circuit Be able to apply the mesh current method to calculate voltage, current, and power in an electric circuit ************************************** Recall that the mesh current method is only valid for non planar circuits. For the mesh current method, use KVL to describe a circuit in terms of b (n 1) independent simultaneous equations. A mesh current is the current that exists only in the perimeter of a mesh. Note that Figure 4.18 illustrates mesh currents and Figure 4.4 illustrates branch currents. It should be evident that it is not always possible to identify a mesh current in terms of a branch current. In order to implement the mesh current method, 1. Assign mesh current i 1, i 2,.... i n to the n meshes in the circuit 2. Apply KVL to each of the n meshes. Use Ohm s law to express the voltages in terms of the mesh currents 3. Solve the resulting n simultaneous equations to get the mesh currents. 4. Determine the relationship between the mesh currents and branch currents in order to find all the voltage and power in the circuit Similar to the analysis with dependent sources for the node voltage method, the existence of a dependent source must be supplemented by an appropriate constraint equation. Concept Question: In the following circuit, all of the light bulbs are identical. Knowing that the intensity of a light bulb is proportional to the power dissipated across it. When the switch is closed, which of the following statements is true? a) Bulb B is brighter b) Bulb B is dimmer c) Bulb B remains the same d) none of the above C.A. Berry Lec4 3.docx Page 1 of 4

54 In Class Activity 1: For the above circuit, use the mesh current method to find all of the mesh currents and confirm that it satisfies the law of conservation of energy. Element V (V) I (A) P del (W) P abs (W) 80 V 5 Ω 30 Ω 90 Ω 26 Ω 8 Ω TOTAL C.A. Berry Lec4 3.docx Page 2 of 4

55 In Class Activity 2: For the following circuit, use the mesh current method to find the mesh currents and voltages across the 8Ω and 6Ω resistors. Compare your solution to the result of Lecture 4 2 In Class Activity 2. C.A. Berry Lec4 3.docx Page 3 of 4

56 In Class Activity 3: For the following circuit, find the power developed in the dependent voltage source. C.A. Berry Lec4 3.docx Page 4 of 4

57 Lecture 5 1 Mesh current method (special cases) Reading: Objectives: Be able to apply the mesh current method to circuits with current sources to solve for voltage, current, and power ************************************** Recall that the mesh current method uses KVL to determine the unknown mesh currents in a circuit. The steps to implement the mesh current method include labeling the meshes, write the KVL equation for each mesh, and solve the simultaneous set of equations. FE Preview: What is the current, I B, through the 40 V battery? a) 1.3 A b) 2.9 A c) 6.7 A d) 13 A Just like there was a special case of the node voltage method when it involves voltage sources, there are also special cases of the mesh current method when a current source is shared between meshes or on an outer branch of a circuit. The following 2 circuits give illustrations of how current sources affect mesh analysis. (a) current source only in one mesh (b) two meshes have the current source in common CASE I CURRENT SOURCE IN ONLY ONE MESH When a current source exists only in one mesh, the mesh current is equal to the value of the source. The sign is dependent upon the direction of the source current. For the circuit in (a) i 2 = 5A. C.A. Berry Lec5 1.docx Page 1 of 4

58 CASE II TWO MESHES HAVE THE CURRENT SOURCE IN COMMON When the current source exists between two meshes, create a supermesh by excluding the current source and any elements connected in series with it. If a circuit has two or more supermeshes that intersect, they should be combined for form a larger supermesh. A supermesh results when two meshes have a (dependent or independent) current source in common. Properties of a supermesh: 1. The current source in the supermesh provides the constraint, (i.e., i 2 i 1 = 6A) 2. A supermesh has no current of its own 3. A supermesh requires the application of both KVL and KCL (i.e., 20 + v 6Ω + v 10Ω + v 4Ω = 0) Node Voltage Method versus Mesh Current Method Networks that contain many series connected elements, voltage sources, or supermeshes are more suitable for mesh analysis. Networks with parallel connected elements, current sources, or supernodes are more suitable for nodal analysis. A circuit with fewer nodes than meshes is better analyzed using nodal analysis. A circuit with fewer meshes than nodes is better analyzed using mesh analysis. The key is to select the method that results in the smaller number of equations. Also, consider the information that is required. If node voltages are required, it may be expedient to apply node analysis. If branch or mesh currents are required, it may be more expedient to use mesh analysis. Concept Question: For the following circuit, would you select the node voltage or mesh current method to solve for the voltage across each passive circuit element? Why? C.A. Berry Lec5 1.docx Page 2 of 4