CHAPTERS 2 & 3 CHAPTERS 2 & 3 NETWORKS 1: NETWORKS 1: September 2002 – Lecture 2b ROWAN UNIVERSITY College of Engineering Professor Peter Mark Jansson, PP PE DEPARTMENT OF ELECTRICAL & COMPUTER ENGINEERING Autumn Semester 2002

networks I Announcements – Homework 1 answers posted today  Returned next Monday Homework 2 is posted on web First Test is in 1 week  Ch. 3: 24 Sep Lab 1 assignment is due in 1 week  Sec 1: 23 Sep  Sec 2: 24 Sep

networks I Today’s Learning Objectives – Define open and short circuit elements Analyze independent electrical sources Analyze dependent sources  VCVS, VCCS, CCVS, CCCS Analyze DC circuits with passive and active elements including: resistance and power sources Introduce Kirchhoff’s Laws

chapter 2 - overview engineering and linear models - done active and passive circuit elements -done resistors – Ohm’s Law - done independent sources dependent sources transducers switches

open & short circuits Open - a break in the circuit where no current flows. Short - a connector between two elements with no voltage drop. open i(t) = 0 v(t)  0 (if there is a source in the circuit) short v(t) = 0 i(t)  0 (if there is a source in the circuit)

sources A “thing” that can supply energy. The energy can come in the form of:  current  voltage  power? There are two types of sources: Independent - constant no matter what you hook it to. Dependent - the value is tied to some other point in the circuit.

ideal independent sources  Ideal independent sources maintain their assigned value indefinitely. i(t) v(t) + – Voltage source An ideal voltage source will maintain its voltage value and sustain ANY value of current. An ideal current source will maintain its current value and sustain ANY value of voltage. i(t)v(t) + – Current source

sources / series connections series – elements connected in series have the same current running through them 20  V= 5v 10  + _ + _ + _ i

sources / parallel connections parallel – elements connected in parallel have the same voltage I i1i1 i2i2 i3i3 R1R1 R2R2 R3R3 +v_+v_

ideal dependent sources  Voltage and current sources can be controlled by either a voltage or a current somewhere else in the circuit. + – v d = r i c or v d = b v c i d = g v c or i d = d i c r, b, g and d are the gains of these sources voltage sourcescurrent sources

the key dependent sources CCVS: current-controlled voltage source VCVS: voltage-controlled voltage source VCCS: voltage-controlled current source CCCS: current-controlled current source

examples CCCS: exercise VCCS: exercise CCVS: exercise 2.8-3

a very important example b e c cb e + v be – + v be – rprp i c = g m v be icic icic

transducers devices that convert physical quantities into electrical quantities: pressure temperature position - potentiometer

switches SPST SPDT Make before break SPDT

ch. 1 & 2 important concepts Circuits; current; voltage; power Passive sign convention Active and Passive elements Linearity - superposition + homogeneity Resistors and Ohm’s Law Sources - Ideal, independent and dependent Opens and Shorts Switches

WHAT DO YOU KNOW (or, what’s going to be on the test)?

Homework for next Monday 9.23 show all work for any credit Dorf & Svoboda, pp Problems 2.3-1, 2.3-2, 2.3-6, 2.4-1, 2.5-1, 2.5-3, 2.5-5, 2.5-7, 2.6-1, 2.6-2, Verification Problem 2-2 Design Problem 2-1

chapter 3 - overview electric circuit applications define: node, closed path, loop Kirchoff’s Current Law Kirchoff’s Voltage Law a voltage divider circuit parallel resistors and current division series V-sources / parallel I-sources resistive circuit analysis

electric circuit applications electric telegraph transatlantic cable engineers vs. scientists those who can do, those who can’t teach?

resistive circuits we are ready to make working circuits with resistive elements and both independent and dependent sources. words we know: short, open, resistor new words: node closed path loop

more definitions node: a junction where two or more are connected closed path: a traversal through a series of nodes ending at the starting node loop:

+ – NODE V R1R1 R2R2 PATH OR LOOP ARE THESE TWO NODES OR ONE NODE? an illustration

Gustav Robert Kirchhoff two laws in 1847 how old was he?

Kirchhoff’s laws Kirchhoff’s Current Law (KCL): at any instant is zero. Kirchhoff’s Voltage Law (KVL): The algebraic sum of the voltages around any closed path in a circuit is zero for all time.

KCL Assume passive sign convention R 2 = 20  I=5A R 1 =10  R 3 = 5  + _ + _ + _ Node 1Node 2 Node 3

R 2 = 20  I=5A R 1 =10  R 3 = 5  v 2 =20v + _ v 3 =20v + _ v 1 =50v+ _ i1i1 i2i2 i3i3 I Node 1 +I - i 1 = 0 Node 2 +i 1 - i 2 - i 3 = 0 Node 3 +i 2 + i 3 - I = 0 i 2 = v 2 /R 2 i 3 = v 3 /R 3 Node 1Node 2 Node 3 Use KCL and Ohm’s Law

KVL +V - v R1 - v R2 = 0 i V = i R1 = i R2 = i +V = iR 1 + iR 2 V = i(R 1 + R 2 ) R 2 = 20  V= 5v R 1 =10  + _ + _ LOOP 1 + _ Start i = V/(R 1 + R 2 ) v R! = iR 1 = VR 1 /(R 1 + R 2 ) v R2 = iR 2 = VR 2 /(R 1 + R 2 )

SERIES RESISTORS +V - v R1 - v R2 = 0 i V = i R1 = i R2 = i +V = iR 1 + iR 2 V = i(R 1 + R 2 ) R 2 = 20  V= 5v R 1 =10  + _ + _ LOOP 1 + _ Start i = V/(R 1 + R 2 ) v R! = iR 1 = VR 1 /(R 1 + R 2 ) v R2 = iR 2 = VR 2 /(R 1 + R 2 ) VOLTAGE DIVIDER NOTE

SERIES RESISTORS resistors attached in a “string” can be added together to get an equivalent resistance. R = 2  R = 3  R = 4  R = 9 

One Minute Paper please complete handout no names leave in box on leaving thanks