EET101 LITAR ELEKTRIK 1ELECTRIC CIRCUIT 1

SEM 1 2008 09

Lecturer : Wan Nur Suryani Firuz Bt Wan Ariffin

Office: KKF 8C

Email : suryanifiruz@unimap.edu.my

Reference Book: 1. Fundamentals of Electric Circuits – Alexander sadiku (3rd edition)

2. Electric Circuits Fundamentals – FLOYD (7Th edition)

3. Basic Engineering Circuit Analysis – J.David Irwin & R.Mark Nelms( 9th edition)

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Chap 1 : Circuit Elements and VariablesOverview of circuit analysis, SI unit, voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source, Ohm’s Law, Kirchhoff’s Law, circuit model, circuit with dependent source. Chap 2 : Resistive CircuitSeries / Parallel circuit, voltage divider circuit, current divider circuit, voltage and current measurement, Wheatstone Bridge, equivalent circuit for delta-wye (Pi-Tee).

Chap 3 : Circuit Analysis Methods Introduction to the Node-Voltage Method, the Node-Voltage Method with dependent sources and special cases, introduction to Mesh-Current Method, Mesh-Current Method with dependent sources and special cases, source transformations, Thevenin and Norton equivalent circuit, maximum power transfer and superposition. Chap 4 : Inductance and CapacitanceInductor, relationship between voltage, current, power and energy, capacitor, relationship between voltage, current, power and energy, series-parallel combinations for inductance and capacitance.

Chap 5 : First-Order and Second-Order Response of RL and RC Circuit Natural response of RL and RC Circuit, Step Response of RL and RC Circuit, general solutions for natural and step response, sequential switching, introduction to the natural and step response of RLC circuit, natural response of series and parallel RLC circuit, Step response of series and parallel RLC circuit. Chap 6: Sinusoidal Steady-State AnalysisThe sinusoidal source, the sinusoidal response, the phasor and phasor diagram, the passive circuit elements in the frequency domain, impedances and reactances, Kirchhoff’s Laws in frequency domain, techniques of circuit analysis in frequency domain Chap 7 : Sinusoidal Steady-State Power CalculationInstantanenous power, average (active) and reactive power, the rms value power calculation, complex and power triangle , the maximum power transfer Chap 8 : Three Phase System CircuitSingle and Three Phase System (Y and Δ circuit), balanced three phase voltage sources, Y – Y circuit analysis, Y - Δ circuit analysis, power calculation in three phase balanced circuit, average power measurement in three phase circuit.

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COURSE STRUCTURE

• Final Exam = 50%• Laboratory = 20%• Test (2 test) = 20%

Test 1 – 6 September 2008Test 2 – 18 October 2008

• Assignment = 10%Group & Tutorial

Total : =100%

Basic electric circuit concepts

• Review SI • Know the definition of basic electrical

quantities : voltage, current, and power• Know the symbols for and definition of

independent and dependent sources• Be able to calculate the power absorbed

by a circuit element using the passive sign convention

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• Voltage,currents, power, energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

SI UNIT• Unit SI

SI : International System of Unit is used by all the major engineering societies and most engineers throughout the world.

Quantity Base unit Symbol

Length Meter m

Mass Kilogram kg

Time second s

Electric current Ampere A

Thermodynamic temperature

Kelvin K

Luminousintensity

candela cd

• Standardized prefixes to signify powers of 10

Power Prefix Symbol

1012 Tera T

109 Giga G

106 Mega M

103 Kilo k

100

10-3 Mili m

10-6 Micro µ

10-9 Nano n

10-12 Pico p

10-15 Femto f

10-18 Atto a

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• Voltage, currents, power, energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

ELECTRIC UNITS

• Charge »»» Coulomb (C)• Current »»» Ampere (A)• Voltage »»» Volt (V)• Resistance »»» Ohm ()• Power »»» Watt (W)

Electric charge is a property possessed by both electrons and protons.

Quantity is

CHARGE (Q)

COULOMB (C)Base Unit is

Examples of correct usage:

Charge = 15 Coulombs

Q = 15 C

Current is the movement of charge in a specified direction.

CURRENT

Electric Current Terminology

Quantity is CURRENT (I)

AMPERE (A)Base Unit is

Examples of correct usage:Current = 12 Amperes

I = 12 A

An ampere equals a coulomb per second.

Electric Current Relationships

Current = I =

Examples:

Charge Time

Qt

I = Qt =

14 C 10 s

= 1.4 A

t = QI =

14 C 1.4 A

= 10 s

Types of current:i

t

i

t

Direct current (arus terus)Alternating current

(arus ulangalik)

Damped alternating current(arus ulangalik teredam) Exponential current

ACDC

ex: Used to run

refrigerator,

stove, washing

machine, and so

on…

ex batteries – used in

automobiles or flashlight

• Voltage is the electric pressure or force that causes current.

• It is a potential energy difference between two points.

• It is also known as an electromotive force (emf) or potential.

Definition of Voltage

VOLTAGE

Voltage Terminology

Quantity is VOLTAGE (V)

VOLT (V)Base Unit is

Examples of correct usage:Voltage = 32 Volts

V = 32 V

A volt equals a joule per coulomb.

Voltage Relationships

Voltage = V =

Examples:

EnergyCharge

WQ

V = WQ =

56 J 2 C

= 28 V

Q = WV =

84 J 21 V

= 4 C

Resistance is the oppositiona material offers to current.

Resistance is determined by:

• Type of material (resistivity)

• Temperature of material

• Cross-sectional area

• Length of material

Definition of Resistance

RESISTANCE

Some Factors That Determine Resistance

For a specific material and temperature, this block has given amount of resistance.

Doubling the length of the block, Doubling the cross-sectional area,

doubles the resistance.halves the resistance.

Resistance Terminology

Quantity is RESISTANCE (R)

OHM ()Base Unit is

Examples of correct usage:

Resistance = 47 ohmsR = 47

An ohm equals a volt per ampere.

Resistance Relationships

Resistance = R =

Example:

Resistivity x length area

KLA

R = KLA

=

= 0.1

1.4 x10-6 cm x 2 x104 cm 0.28 cm2

Work (W)consists of a force moving through a distance.

Energy (W)is the capacity to do work.

The joule (J)is the base unit for both energy and work.

The amount of work done equals the amount of

energy used (converted).

Fifty joules of energy are

required to do fifty joules of

work.

ENERGY

Power is the rate of using energy or doing work.

“Using energy” means that energy is being converted to a different form.

Definition of Power

POWER

Power Terminology

Quantity is POWER (P)

WATT (W)Base Unit is

Examples of correct usage:

Power = 120 Watts

P = 120 W

A watt equals a joule per second.

Power Relationships

Power = P =

Examples:

Energy Time

W t

P = W t =

158 J 20 s

= 7.9 W

W = Pt = 75 W x 25 s = 1875 J

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• voltage and currents, power,

energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

ACTIVE AND PASSIVE ELEMENTS

Circuit Elements

Active elements•capable of generating electric energy•Example : voltage and current sources

Passive elements•incapable of generating electric energy•Example : resistore, inductor, capacitor, diode and etc

Independent source

Voltage

Current

Dependent source

xs iV xs Vi

Voltage Current

Ideal voltage source connected in series

Ideal current source connected in parallel

Symbol of circuit elements

• Resistor

RUNIT: Ohm (Ω)

Resistor colour code

Resistor Colour Codes

Yellow

4 10 %

Silver

7

Violet

00

Red

Resistor Colour Codes

Green = 5 Blue = 6 Orange = 3 Gold = 5 %

56 x 103 5 % =56000 5 % = 56 k 5 %

Resistor Colour Codes

4 0 0 06 4 2% = 464 k 2%

Conductance

• Conductance is a measure of the ability of an element to conduct electric current

• Inverse of resistance• Units: Siemens (S) or mhos

v

i

R

1G

• Capacitor

CUNIT: Farad (F)

• Inductor

LUNIT: Henry (H)

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• voltage and currents, power,

energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

Short Circuit– R = 0 no voltage difference exists – all points on the wire are at the same

potential.– Current can flow, as determined by

the circuit

Open circuit

– R = no current flows– Voltage difference can exist, as

determined by the circuit

Circuit Nodes and Loops

• A node is a point where two or more circuit elements are connected.

• A loop is formed by tracing a closed path in a circuit through selected basic circuit elements without passing through any intermediate node more than once

Example: Find the Nodes

+

-Vs

node

Example: Find the loops

loop

OHM LAW

• George Simon Ohm (1787-1854) formulated the relationships among voltage, current, and resistance as follows:

The current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit.

IRV

KIRCHHOFF LAW

• Gustav Robert Kirchhoff (1824 – 1887)

• Models relationship between:– circuit element currents (KCL)– circuit element voltages (KVL)

• Introduce two laws:– Kirchhoff Current Law (KCL)– Kirchhoff Voltage Law (KVL)

• Current entering node = current exiting(What goes in, must come out)

• Convention: +i is exiting, -i is entering• For any circuit node:

0i

Kirchhoff’s Current Law (KCL)

Kirchhoff’s Current Law (KCL)

No matter how many paths into and out of a single point all the current leaving that point must equal the current arriving at that point.

• voltage increases = voltage decreases(What goes up, must come down)

• Convention: hit minus (-) side first, write negative

• For any circuit loop:

0v

Kirchhoff’s Voltage Law (KVL)

Kirchhoff’s Voltage Law (KVL)

The voltage drops around any closed loop must equal the applied voltages

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• voltage and currents, power,

energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

PARALLEL-SERIES

CIRCUIT MODEL

SERIES PARALLEL

This complete circuit uses the following:

•An energy or power source

•A control device•A load•Conductors •Insulation (not shown)

Calculating Current

I =VR

= 36 V1800

= 0.02 A = 20 mA

S1

SPST

R

1.8 k

B1

36 V

Calculating Resistance

R = V I =

24 V 0.03 A

= 800 = 0.8 k

R

B1

24 V

A0.03 A

Calculating Voltage

V = IR = 0.15 A x 270 = 40.5 V

R

B1

A0.15 A

Calculating Power

P =

0.2 A

IV = 0.2 A x 54 V= 10.8 W

V54 V

P = I2R = 0.2 A x 0.2 A x 270 = 10.8 W

P = V2/R = (54 V x 54 V) / 270 = 10.8 W

A

CIRCUIT ELEMENTS & VARIABLES

• Overview of circuit analysis• SI unit• voltage and currents, power,

energy, • elements on the circuit (passive

and active) voltage and current source

• Ohm’s Law and Kirchhoff’s Law• circuit model• circuit with dependent source.

CIRCUIT WITH DEPENDENT SOURCE

• Using KVL on the first loop,

0205500 ii

• Using KCL on the second loop,

ii

iii

6

5

0

0

• Solve the equations,

Ai

Ai

24

4

0

• Using Ohm law for the resistor,

V480

)20(iv o0