Topic 4
Engineering 1333: Electrical Circuits
The Kirchhoff Laws
(Sections 2.3 & 2.4)
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Kirchoff Laws
1
A Circuit
R1
Heres a circuit with one
voltage source and
several resistors
i4
+
+
vs
R3

Wed like to solve the circuit.
That is wed l
Topic 8
Engineering 1333: Electrical Circuits
Voltage and Current Division
(3.3 & 3.4)
Symbol & MT Extra
included
The Voltage Divider
+
vs v1 + v2
=
The same current i flows through all
the resistors
vs = iR1 + iR2 = i ( R1 + R2 )
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vs
R1 + R2

Topic 5
Engineering 1333: Electrical Circuits
Riding the Hills
(2.4)
5/29/2014
Riding the Hills
1
The Telegraph Hill Bike Race
5/29/2014
Riding the Hills
2
1
3
Write KVL
around the
four loops
shown
+

+
va
vb
v5

+
v4
c
5
vc
6
e
4

+
v3
b
v2


a
+
v1
Topic 11
Engineering 1333: Electrical Circuits
SuperNodes
(4.4)
Is
Special Cases
There are 3 essential nodes
in this circuit, implying two
unique node equations
Choosing a ground node
v1
v2
vi
+
R2

R1
R3
Would normally leave us
with two nodes at which
Topic 13
Engineering 1333: Electrical Circuits
Superposition
(4.13)
1k
2k
Well use the mesh method
to solve this circuit.
+
A Simple Circuit
4

ia
ib
5k
2mA
Since ib is the only mesh current
ib = 2
through the current source branch,
it is specified alrea
Topic 3
Engineering 1333: Electrical Circuits
Sources and Resistance
(Sections 2.1 & 2.2)
12Sep07
Sources and Resistance
1
Independent Voltage Sources
i
+
vs
+
v

The ideal voltage source produces a fixed voltage
across itself no matter what current pa
Topic 7
Engineering 1333: Electrical Circuits
Resistors in Series and Parallel
(3.1 & 3.2)
Resistors in Series
i
R1
R3
+
vs
R2
If one bulb burns out
all the lights go out
because no current
can flow
R4

R6
R5
The circuit contains a single voltage source
Topic 2
Engineering 1333: Electrical Circuits
Power & Energy
(Section 1.6)
Sample Problem 1.3
+
1
v
i

2
Calculate the total charge in
microCoulombs entering the
device at terminal 1
Solution
By definition
so
dq
i=
dt
dq = i dt
Since this is in coulombs
Introduction
Engineering 1333: Electrical Circuits
Voltage, Current, Charge
and Energy
(Sections 1.3 1.5)
Consider potential energy of a mass held at a height
m
g
E=mgh
h
Notice that height is a doubleended measurement
It is the distance between two point
Topic 6
Engineering 1333: Electrical Circuits
Analysis with Dependent Sources
(2.5)
vab = 5i = 5 4 = 20 v
Objective
5
a
Find vo in the circuit
io
+
i
+
500v
b
20
vo

5i

Look for interim objectives
c
1. If we know io then we can
find vo by Ohms Law
By K
Topic 9
Engineering 1333: Electrical Circuits
Node Voltages
(4.2)
Symbol & MT Extra
included
Point Voltages
+
v1

Voltage is an across measurementlike height
+
+
We measure the voltages across the
three components, vs, v1 & v2
vs
v2


We can make vol
Topic 10
Engineering 1333: Electrical Circuits
The NodeVoltage Method
(4.1, 4.2 & 4.3)
Some Terminology (table 4.1 from text)
Name
Definition
node
A point where two or more circuit elements join
essential node
A node where three or more circuit elements
Topic 14
Engineering 1333: Electrical Circuits
Thevinin & Norton Equivalents
(4.94.12)
Source Transformations
We add a load
iL
R
+
vs
+
vL =
RL vL


RL
vs
R + RL
vs
iL =
R + RL
RL
RL
vL
vs = vs
RL
If
We have a circuit with just a voltage
source, a se