EET101 LITAR ELEKTRIK 1
ELECTRIC 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)
Syllabus - EET 101
Chap 1 : Circuit Elements and 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, Kirchhoff’s Law, circuit model, circuit with
dependent source.
Chap 2 : Resistive Circuit
Series / 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 MeshCurrent 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 Capacitance
Inductor, relationship between voltage, current, power and energy,
capacitor, relationship between voltage, current, power and energy,
series-parallel combinations for inductance and capacitance.
Syllabus - EET 101
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 Analysis
The 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 Calculation
Instantanenous power, average (active) and reactive power, the rms
value power calculation, complex and power triangle , the maximum
power transfer
Chap 8 : Three Phase System Circuit
Single 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.
COURSE STRUCTURE
• Final Exam
• Laboratory
• Test (2 test)
= 50%
= 20%
= 20%
Test 1 – 6 September 2008
Test 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
Luminous
intensity
Kelvin
K
candela
cd
• Standardized prefixes to signify powers of 10
Power
Prefix
Symbol
1012
Tera
T
109
Giga
G
106
Mega
M
103
Kilo
k
10-3
Mili
m
10-6
Micro
µ
10-9
Nano
n
10-12
Pico
p
10-15
Femto
f
10-18
Atto
a
100
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
Current
Voltage
Resistance
Power
»»»
»»»
»»»
»»»
»»»
Coulomb (C)
Ampere (A)
Volt (V)
Ohm ()
Watt (W)
Electric charge is a property
possessed by both electrons and
protons.
Quantity is
CHARGE (Q)
Base Unit is
COULOMB (C)
Examples of correct usage:
Charge = 15 Coulombs
Q = 15 C
CURRENT
Current is the movement
of charge in a specified
direction.
Electric Current Terminology
Quantity is
CURRENT (I)
Base Unit is
AMPERE (A)
An ampere equals a coulomb per second.
Examples of correct usage:
Current = 12 Amperes
I = 12 A
Electric Current Relationships
Charge
Current =
Time
Q
I= t
Examples:
Q
14 C = 1.4 A
I = t = 10 s
Q
14 C = 10 s
t = I = 1.4 A
Types of current:
i
DC
AC
ex batteries –
used in
automobiles
or flashlight
t
Alternating current
(arus ulangalik)
Direct current (arus terus)
i
t
Damped alternating current
(arus ulangalik teredam)
Exponential current
VOLTAGE
Definition of Voltage
• 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.
Voltage Terminology
Quantity is
VOLTAGE (V)
Base Unit is VOLT (V)
A volt equals a joule per coulomb.
Examples of correct usage:
Voltage = 32 Volts
V = 32 V
Voltage Relationships
Energy
Voltage =
Charge
Examples:
W
V= Q =
W
V= Q
56 J = 28 V
2C
84 J = 4 C
W
Q = V = 21 V
RESISTANCE
Definition of Resistance
Resistance is the opposition
a material offers to current.
Resistance is determined by:
• Type of material (resistivity)
• Temperature of material
• Cross-sectional area
• Length of material
Some Factors That Determine Resistance
For a specific material and temperature,
this block has given amount of resistance.
Doubling the length of the block, doubles the resistance.
Doubling the cross-sectional area, halves the resistance.
Resistance Terminology
Quantity is
RESISTANCE (R)
Base Unit is
OHM ()
An ohm equals a volt per ampere.
Examples of correct usage:
Resistance = 47 ohms
R = 47 
Resistance Relationships
Resistivity x length
KL
Resistance =
R= A
area
Example:
1.4 x10-6  cm x 2 x104 cm
KL
=
R=
A
0.28 cm2
= 0.1 
ENERGY
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.
POWER
Definition of Power
Power is the rate of using
energy or doing work.
“Using energy” means that energy
is being converted to a different
form.
Power Terminology
Quantity is
POWER (P)
Base Unit is WATT (W)
A watt equals a joule per second.
Examples of correct usage:
Power = 120 Watts
P = 120 W
Power Relationships
Energy
Power =
Time
W
P= t
Examples:
158 J = 7.9 W
W
P = t = 20 s
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
Current
Voltage
Dependent source
Vs  ix
is  Vx
Voltage
Current
Ideal voltage source connected in
series
Ideal current source connected
in parallel
Symbol of circuit elements
• Resistor
R
UNIT: Ohm (Ω)
Resistor colour code
Resistor Colour Codes
Yellow
Violet
Red
Silver
4700 ±10 %
Resistor Colour Codes
Green = 5
Blue = 6
Orange = 3
Gold = ± 5 %
56 x 103 ± 5 % = 56000 ± 5 % = 56 k ± 5 %
Resistor Colour Codes
4 6 4 0 0 0 ± 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
1 i
G 
R v
• Capacitor
C
UNIT: Farad (F)
• Inductor
L
UNIT: 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.
V  IR
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)
Kirchhoff’s Current Law (KCL)
• Current entering node = current exiting
(What goes in, must come out)
• Convention: +i is exiting, -i is entering
• For any circuit node:
i

0

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.
Kirchhoff’s Voltage Law (KVL)
• voltage increases = voltage decreases
(What goes up, must come down)
• Convention: hit minus (-) side first, write
negative
• For any circuit loop:
v

0

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.
CIRCUIT MODEL
SERIES
PARALLEL
PARALLEL-SERIES
This complete circuit uses the following:
•An energy or power source
•A control device
•A load
•Conductors
•Insulation (not shown)
Calculating Current
S1
B1
36 V
SPST
R
1.8 k
V
36
V
= 0.02 A = 20 mA
I=
=
R
1800 
Calculating Resistance
A
B1
24 V
0.03 A
R
V
24 V
R= I =
= 800  = 0.8 k 
0.03 A
Calculating Voltage
A
B1
0.15 A
R
270 
V = IR = 0.15 A x 270  = 40.5 V
Calculating Power
A
V
0.2 A
54 V
270 
P = IV = 0.2 A x 54 V = 10.8 W
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
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,
500  5 i  20 i0
• Using KCL on the second loop,
i0  i  5 i
i0  6i
• Solve the equations,
i  4 A
i0  24 A
• Using Ohm law for the
resistor,
v 0  i o (20)
 480V