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EEEB1113
CircuitAnalysisI
Chapter 1Basic circuit elements and quantities concepts
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LearningObjectivesLecture 1
Welcome and Introduction
Lecture 2
Understand the range ofSI prefixes and notation. Develop an understanding of the concepts ofvoltage, current,and power and their role in the context of an electrical circuit. Introduce the concepts ofDC and AC electrical currents.
Lecture 3
Understand the concept of voltage and current sources2
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WhatiscoveredinTodayLecture:
OCircuit and circuit modelOCircuit VariablesOCircuit Elements
3
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Circuitand
circuit
model
O Actual electrical component: a battery and a light bulb
4
Ideal circuit component: a
mathematical model of an actual
electric component.
Actual electrical
component
Ideal circuit
component Circuit Model
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Circuit model: A commonly used mathematical model forelectric system.
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CircuitElement
O There are two types of elements:
a. Passive elements - cannot generate energy, i.e resistors,
capacitors and inductor.
b. Active elements - can generate energy, i.e batteries,generators, current or voltage sources.
O There are two kinds of sources:
a. An active element that provides voltage or current thatindependent of other circuit elements is called independent
sources
b. An active element that depends on voltage or current of other
element is called dependent sources
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VoltageandCurrentSources
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An ideal independent source is an active element that
provides a specified voltage or current that is completely
independent of other circuit variables.
Symbols for independent voltage source Symbols for independent current source
The voltage is determined by itself but the current through it
is determined by the outside circuit
independent sources
dependent sources
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Note:
2 or more voltage sources with different value are not permissible
to be connected in parallel
2 or more current sources with different value are not permissible
to be connected in series
Voltage sources connected in series is equivalent to one voltage
source
Current sources connected in parallel is equivalent to one current
source
A voltage source connected to any branch in parallel is equivalent
to itself
A current source connected to any branch in series is equivalent to
itself
VoltageandCurrentSources
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An ideal dependent (or controlled) source is an activeelement in which the source quantity is controlled by
another voltage or current.
Symbols for a) dependent voltage sources b) dependentcurrent sources
There are a total of four variations
1. A voltage controlled voltage source (VCVS)
2. A current controlled voltage source (CCVS)
3. A voltage controlled current source (VCCS)
4. A current controlled current source (CCCS)
VoltageandCurrentSources
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What is the difference between independent
and dependent sources?
VCVS CCVS
VCCS CCCS
VoltageandCurrentSources
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O A voltage or current source whose value
depends on the value of voltage or current
elsewhere in the circuit
O Use a diamond-shaped symbol
Vs
1 V/V Vs=uVxVx
+
-
+
-
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VoltageandCurrentSources
Controlled
or
Dependent
Sources
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Vs
1 V/VVs=uVxVx
+
-
+
-
O Vs is the outputvoltage
O Vx is the reference
voltage
O u is the multiplier
O Vs = uVx
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VoltageandCurrentSources
Voltage
Controlled
Voltage
Source
VCVS
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VoltageandCurrentSources
Current
Controlled
Voltage
Source
CCVS
Vs
1 Ohm Vs=pIx
-
+
Ix
O Vs is the outputvoltage
O Ix is the reference
current
O p is the multiplier
O Vs = pIx
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VoltageControlled
Current
Source
VCCS
Is
1 MhoVx
+
-
Is = aVx
O Is is the outputcurrent
O Vx is the reference
voltageO a is the multiplier
O Is = aVx
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VoltageandCurrentSources
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CurrentControlled
Current
Source
CCCS
Is
1 A/AIx Is=bIx
O Is is the outputcurrent
O Ix is the reference
current
O b is the multiplier
O Is = bIx
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VoltageandCurrentSources
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Dependent Voltage Sources
+
6Vx
Voltage-ControlledVoltage Source
(VCVS)
6000Ix
Current-Controlled
Voltage Source
(CCVS)
+
Example:
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Dependent Current Sources
0.006Vx
Voltage-ControlledCurrent Source
(VCCS)
6Ix
Current-Controlled Current
Source (CCCS)
Example:
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oltageandCurrentSources
Dependent
(Controlled)
Source
ExampleIn the following circuits, identify the type of dependent sources:
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ActiveandPassiveElements
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O Active elementO a device capable of
generating electricalenergy
O Voltage source
O Current sourceO Power source
O Batteries
O Generators
O a device that needs to
be powered (biased)O transistor
O Passive elementO a device that
absorbs electricalenergy
O ResistorO Capacitor
O Inductor
O motor
O light bulbO heating element
Vo tagean urrent ourcesDependent(Controlled)Source Example
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EndofChapter1
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