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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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