EE201 Fundamentals of Electric Circuits
Instructor:
Dr. Ali M. Eltamaly, Office: 2C20, eltamaly@ksu.edu.sa
Phone: 4676-828
Website: faculty.ksu.edu.sa/eltamaly
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Text Book:
“Introductory Circuit Analysis” By Robert L. Boylestad, 10th Edition, Published by
Prentice Hall, 2001.
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Mid term tests:
First mid-term Exam:
Tuesday, 22/11/1430 H (10/11/2009)
Second Mid-Term Exam:
Sunday, 26/12/1430 H (13/12/2009)
Third Mid-Term Exam:
Tuesday, 26 /1/1431 H (12/1/2010)
Notes:
1. The best two mid-term exams will be counted
2 All mid-term
2.
id t
exams will
ill bbe performed
f
d after
ft Maghreb
M h b prayers
3. If you miss any mid-term exam, there will be no make up test for any given reasons
Grading
g Policy:
y
Mid-Term Exams:
Home Works + Quizzes
Final Exam
50%
10%
40%
Chapters
Definitions and Laws
1-4
Series/Parallel (DC) circuits
analysis
5-8
Network Theorems (DC) circuits
9
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Topic
13-14
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Sinusoidal alternating and phasors
15 17
15-17
Network Theorems (AC) circuits
18
Power ((AC))
19
Polyphase Systems
22
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Series/Parallel
S
i /P ll l (AC) circuits
i it
analysis
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Course outline:
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Texas Instruments TI-89 calculator.
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FIG. 1.5
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POWERS OF TEN
Chapter 2 Current and Voltage
Current and Voltage
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ATOMS AND THEIR STRUCTURE
FIG. 2.1
Hydrogen and helium atoms.
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Shells and subshells of the atomic structure.
2n
2
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The atomic structure of copper.
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CURRENT
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If 6.242 * 1018 electrons drift at uniform velocity through the imaginary circular cross
section
sec
o oof Fig.
g. 2.7
.7 in 1 seco
second,
d, thee flow
ow oof ccharge,
a ge, or
o cu
current,
e , iss said
sa d too be 1 aampere
pe e ((A))
VOLTAGE
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A potential difference of 1 volt (V) exists between two points if 1 joule (J) of energy
is exchanged in moving 1 coulomb (C) of charge between the two points.
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Potential: The voltage at a point with respect to another point in the
electrical system. Typically the reference point is ground, which is at
zero potential.
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Potential difference: The algebraic difference in potential (or voltage)
between two points of a network.
network Voltage: When isolated,
isolated like potential,
potential
the voltage at a point with respect to some reference such as ground (0
V).
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Voltage difference: The algebraic difference in voltage (or potential)
between two points of the system. A voltage drop or rise is as the
terminology would suggest.
Electromotive force (emf): The force that establishes the flow of
charge (or current) in a system due to the application of a difference in
potential. This term is not applied that often in today’s literaturebut is
associated primarily with sources of energy.
3 1 – Introduction
3.1
The resistance of any material with a uniform cross-sectional area is
determined by the following factors:
– Material
– Length
– Cross-sectional Area
– Temperature
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•
FIG. 3.1
Resistance symbol and notation.
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Film resistors: (a) construction; (b) types.
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Molded composition-type potentiometer.
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Color coding for fixed resistors.
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FIG. 3.25
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Color coding.
Example 3.13.
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FIG. 3.27
12 * 10 Ω = 12 kΩ
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Five-band color coding for fixed resistors.
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FIG. 3.29
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Chapter 4 – Ohm’s Law, Power and Energy
Developed in 1827 by Georg Simon Ohm
Ohm’s Law
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E
I=
R
Where:
I = current (amperes, A)
E = voltage (volts, V)
R = resistance (ohms, Ω)
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Defining polarities.
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FIG. 4.3
4 4 Power
4.4 ‐
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F Power is an indication of how much work (
(the conversion of energy from one form to gy
another) can be done in a specific amount ;
,
of doing work.
g
of time; that is, a rate
Power
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W
P=
t
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1 Watt ((W)) = 1 jjoule / second
Power can be delivered or absorbed as defined by F
th
the polarity of the voltage and the direction of the l it f th
lt
d th di ti
f th
current.
4 5 Energy
4.5 ‐
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F Energy (W) lost or gained by any system is determined by:
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W = Pt
F Since power is measured in watts (or joules per second) and time in seconds, the unit of energy is the wattsecond (Ws) or joule (J)
Energy
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The watt
The
watt‐second
second is too small a quantity for most is too small a quantity for most •
practical purposes, so the watt‐hour (Wh) and kilowatt‐hour (kWh) are defined as follows:
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Energy (Wh) = power (W) × time (h)
power (W) × time (h)
Energy (kWh) =
1000
The killowatt‐hour meter is an instrument used •
for measuring the energy supplied to a residential or commercial user of electricity. id i l
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4 6 Efficiency
4.6 ‐
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Efficiency (η) of a system is determined by F
the following equation: g q
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η = Po / Pi
η = efficiency (decimal number) Where:
Po = power output
Pi = power input
Chapter 5 – Series dc Circuits
Series connection of resistors.
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FIG. 5.4
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RT = R1 + R2 + R3 + R4 + ... + RN
FWhen series resistors have the same value
RT = NR
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Configuration in which none of the resistors are in series.
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FIG. 5.5
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Series connection of resistors for Example 5.1.
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FIG. 5.6
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Schematic representation for a dc series circuit.
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FIG. 5.12
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5.5 ‐ Voltage Sources in Series
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F Voltage sources can be connected in series to increase or
decrease the total voltage
g applied
pp
to the system.
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F Net voltage is determined by summing the sources
having the same polarity and subtracting the total of the
sources having the opposite polarity.
Kirchhoff’s Voltage Law
F The applied voltage of a series circuit equals the sum of the voltage drops across the series g
p
elements:
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= ∑Vdrops
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∑V
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FThe sum of the rises around a closed loop must equal the sum of the drops.
the sum of the drops.
F When applying Kirchhoff’s voltage law, be sure to concentrate on the polarities of the voltage rise or drop rather than on the type of element.
th th
th t
f l
t
F Do not treat a voltage drop across a resistive element differently from a voltage drop across a source.
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Applying Kirchhoff’s voltage law to a series dc circuit.
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FIG. 5.26
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EXAMPLE 5.4
Determine the unknown voltages for the networks of Fig. 5.14.
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EXAMPLE 5.5 Find V1 and V2 for the network of Fig. 5.15
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Notation
FDouble‐subscript notation
F Because voltage is an “across” variable and exists D
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between two points, the double‐subscript notation b
i
h d bl
b i
i
defines differences in potential.
F The double‐subscript notation Vab specifies point a as the higher potential. If this is not the case, a negative sign must be associated with the magnitude of Vab .
F The voltage V
The voltage Vabb is the voltage at point (a)
is the voltage at point (a) with respect with respect
to point (b).
Notation
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F Single‐subscript notation
F The single‐subscript notation V
The single subscript notation Va specifies the specifies the
voltage at point a with respect to ground (zero volts). If the voltage is less than zero volts, a negative sign must be associated with the magnitude of Va .
Notation
F General Relationship
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F If the voltage at points a
g
p
and b are known with respect to ground, then the voltage Vab
can be determined using the following equation:
Vab = Va – V b
5 7 – Voltage Division in a Series Circuit
5.7 –
Voltage Division in a Series Circuit
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F The voltage across the resistive elements will divide as the magnitude of the resistance levels.
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F The greater the value of a resistor in a series circuit, the more of the applied voltage it will capture.
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FV lt
FVoltage Divider Rule (VDR)
Di id R l (VDR)
FThe VDR permits determining the voltage levels of a circuit without first finding the current.
circuit without first finding the current.
E
VX = R X
RT
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Chapter 6 – Parallel dc Circuits
FTwo elements, branches, or circuits are in parallel D
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if they have two points in common as in the figure below
Insert Fig 6.2
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GT = G1 + G2 + G3 + ... + GN
1
RT =
1
1
1
1
+
+
+ ... +
R1 R2 R3
RN
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EXAMPLE 6.3 Determine the total resistance for the network of Fig. 6.8.
Parallel Resistors
Parallel Resistors
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FF
FFor equal resistors in parallel:
l i
i
ll l
Where N = the number of parallel resistors.
EXAMPLE 6.4
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Find the total resistance of the network of Fig. 6.9.
EXAMPLE 6.4
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Calculate the total resistance for the network of Fig. 6.10.
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Parallel Resistors
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EXAMPLE 6.7 Calculate the total resistance of the parallel network of Fig. 6.13.
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EXAMPLE 6.8 Determine the value of R2 in Fig. 6.15 to establish a total resistance of 9 k.
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6.3 – Parallel Circuits
Is = I1 + I 2
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F Voltage is always the same across parallel elements.
V1 = V2 = E
The voltage
g across resistor 1 equals
q
the voltage
g across resistor 2,, and both equal
q
the voltage supplies by the source.
E E
Is = I1 + I 2 =
+
R1 R2
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EXAMPLE 6.12 Given the information provided in Fig. 6.23:
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a. Determine R3.
b. Calculate E.
c. Find Is.
d. Find I2.
e. Determine
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Kirchhoff’ss Current Law
Kirchhoff
Current Law
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F Most common application of the law will be at the junction of two or
more paths
h off current.
F Determining whether a current is entering or leaving a junction is
sometimes the most difficult task.
FIf the current arrow points toward the junction, the current is entering the
junction.
F If the current arrow points away from the junction, the current is leaving
the junction.
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EXAMPLE 6.15 Determine the currents I3 and I5 of Fig. 6.29 through applications
of Kirchhoff’s current law.
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6.6 CURRENT DIVIDER RULE
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V RT IT
Ix =
=
Rx
Rx
RT
IT
Ix =
Rx
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EXAMPLE 6.17 Determine the current I2 for the network of Fig. 6.35 using the current
divider rule.
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EXAMPLE 6.18 Find the current I1 for the network of Fig. 6.36.
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Current seeks the path of least resistance.
RT
Ix =
IT
Rx
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OPEN AND SHORT CIRCUITS
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Determine the unknown voltage and current for each network of Fig. 6.48.
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EXAMPLE 6.25 Determine V and I for the network of Fig. 6.52 if the
resistor R2 is shorted out.