CHAPTERS 2 & 3CHAPTERS 2 & 3

NETWORKS 1: NETWORKS 1: 0909201-010909201-01 17 September 2002 – Lecture 2b

ROWAN UNIVERSITYROWAN UNIVERSITY

College of EngineeringCollege of Engineering

Professor Peter Mark Jansson, PP PEProfessor Peter Mark Jansson, PP PEDEPARTMENT OF ELECTRICAL & COMPUTER ENGINEERINGDEPARTMENT OF ELECTRICAL & COMPUTER ENGINEERING

Autumn Semester 2002Autumn 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 circuitsOpen - 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)+–

Voltagesource

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)

+

–

Currentsource

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

Ii1

i2 i3

R1 R2 R3

+

v

_

ideal dependent sources

Voltage and current sources can be controlled by either a voltage or a current somewhere else in the circuit.

+–

vd = r ic

or

vd = b vc

id = g vc

or

id = d ic

r, b, g and d are the gains of these sources

voltage sources current 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 2.8-1 VCCS: exercise 2.8-2 CCVS: exercise 2.8-3

a very important example

b

e

c cb

e

+

vbe

–+

vbe

–

rp

ic =

gmvbe

ic ic

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; powerPassive sign conventionActive and Passive elementsLinearity - superposition + homogeneityResistors and Ohm’s LawSources - Ideal, independent and dependentOpens 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. 58-63 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, 2.7-1 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

R1

R2PATH OR LOOP

ARE THESE TWO NODES OR ONE NODE?

an illustration

Gustav Robert Kirchhoff

1824-1887 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

R2= 20

I=5A

R1=10

R3= 5+

_

+

_

+ _Node 1 Node 2

Node 3

R2= 20

I=5A

R1=10

R3= 5v2=20v

+

_v3=20v

+

_

v1=50v+ _

i1

i2 i3

I

Node 1 +I - i1 = 0

Node 2 +i1 - i2 - i3 = 0

Node 3 +i2 + i3 - I = 0

i2 = v2/R2 i3 = v3/R3

Node 1 Node 2

Node 3

Use KCL andOhm’s Law

KVL

+V - vR1 - vR2 = 0

iV = iR1 = iR2 = i

+V = iR1 + iR2

V = i(R1 + R2)

R2= 20

V= 5v

R1=10

+

_

+ _

LOOP 1+_

Start

i = V/(R1 + R2)

vR! = iR1 = VR1 /(R1 + R2)

vR2 = iR2 = VR2/(R1 + R2)

SERIES RESISTORS

+V - vR1 - vR2 = 0

iV = iR1 = iR2 = i

+V = iR1 + iR2

V = i(R1 + R2)

R2= 20

V= 5v

R1=10

+

_

+ _

LOOP 1+_

Start

i = V/(R1 + R2)

vR! = iR1 = VR1 /(R1 + R2)

vR2 = iR2 = VR2/(R1 + R2)

VOLTAGE DIVIDER

NOTE

SERIES RESISTORS

resistors attached in a “string” can be added together to get an equivalent resistance.

R = 2 R = 3

R = 4R = 9

One Minute Paper

please complete handout no names leave in box on leaving thanks