chapters 2 & 3 chapters 2 & 3 networks 1: 0909201-01 networks 1: 0909201-01 17 september...
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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
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