CHAPTERS 2 & 3 NETWORKS 1: 0909201-01 17 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 v(t) = 0 i(t) 0 (if there is a source in the circuit) i(t) = 0 v(t) 0 (if there is a source in the circuit) short
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.
i(t) + + v(t) i(t) v(t) – – Currentsource Voltagesource ideal independent sources • Ideal independent sources maintain their assigned value indefinitely. 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.
10 _ + + V= 5v + _ _ 20 sources / series connections • series – elements connected in series have the same current running through them i
i2 i3 i1 + v _ I R1 R2 R3 sources / parallel connections • parallel – elements connected in parallel have the same voltage
ideal dependent sources • Voltage and current sources can be controlled by either a voltage or a current somewhere else in the circuit. voltage sources current sources 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
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 c b c ic ic + vbe – ic = gmvbe b rp + vbe – e e
transducers • devices that convert physical quantities into electrical quantities: • pressure • temperature • position - potentiometer
switches Make before break SPDT SPST 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
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:
PATH OR LOOP an illustration R1 NODE + V R2 – ARE THESE TWO NODES OR ONE NODE?
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.
R1=10 Node 1 Node 2 _ + + + R3= 5 I=5A R2= 20 _ _ Node 3 KCL Assume passive sign convention
R1=10 i1 _ + v1=50v + + I I=5A v2=20v R3= 5 i2 i3 R2= 20 v3=20v _ _ Node 1 Node 2 Node 3 Node 1 +I - i1 = 0 Node 2 +i1 - i2 - i3 = 0 Node 3 +i2 + i3 - I = 0 i2 = v2/R2 i3 = v3/R3 Use KCL and Ohm’s Law
R1=10 _ + + V= 5v + LOOP 1 _ _ R2= 20 Start +V - vR1 - vR2 = 0 iV = iR1 = iR2 = i +V = iR1 + iR2 V = i(R1 + R2) KVL i = V/(R1 + R2) vR! = iR1 = VR1 /(R1 + R2) vR2 = iR2 = VR2/(R1 + R2)
R1=10 _ + + V= 5v + LOOP 1 _ _ R2= 20 Start +V - vR1 - vR2 = 0 iV = iR1 = iR2 = i +V = iR1 + iR2 V = i(R1 + R2) SERIES RESISTORS NOTE i = V/(R1 + R2) vR! = iR1 = VR1 /(R1 + R2) vR2 = iR2 = VR2/(R1 + R2) VOLTAGE DIVIDER
R = 2 R = 3 R = 9 R = 4 SERIES RESISTORS • resistors attached in a “string” can be added together to get an equivalent resistance.
One Minute Paper • please complete handout • no names • leave in box on leaving • thanks