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電路學(一)
Text Book:
Fundamentals of Electric Circuits, by C. K. Alexander and M.
N. O. Sadiku
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Basic Concepts
Basic Laws
Methods of Analysis
Circuit Theorems
Operational Amplifiers
Capacitors and Inductors
First-Order Circuits
Second-Order Circuits
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評分標準
• Homework: 15%
– 一律用A4紙書寫，並裝訂好。遲交的作業：一周內補交成績以80%
採計，隔周起補交打對折。
‧ 期中考: 35%
‧ 期末考: 35%
‧ 隨堂小考、出席狀況: 15%
• 教材密碼:
• E-mail: ycchiang1970@nchu.edu.tw
‧ 個人網頁: http://web.ee.nchu.edu.tw/~ycchiang1970 (或由系
網頁的連結), http://web.nchu.edu.tw/~ycchiang/
‧ 實驗室網頁: http://web.ee.nchu.edu.tw/~rfem
3
Introduction
• Electric Circuit
– An interconnection of electrical elements.
Connecting wires
4
Introduction
5
Introduction
‧ 相關課程
微電子學
物理學
工程數學
電路學
電機機械
微波通訊
電磁學
…
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Systems of Units
• International System of Unit (SI)
– The General Conference on Weights and Measures (1960).
Quantity
Length
Mass
Time
Electric current
Thermodynamic temperature
Luminous intensity
Basic unit
meter
kilogram
second
ampere
Symbol
m
kg
s
A
kelvin
candela
K
cd
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Multiplier
1 000 000 000 000 000 000  1018
1 000 000 000 000 000  1015
Prefix
exa
peta
Symbol
E
P
1 000 000 000 000  1012
1 000 000 000  109
1 000 000  106
1 000  103
100  102
10  101
0.1  101
0.01  102
0.001  103
0.000 001  106
0.000 000 001  109
0.000 000 000 001  1012
0.000 000 000 000 001  1015
tera
giga
mega
kilo
hecto
deka
deci
centi
milli
micro
nano
pico
femto
T
G
M
k
h
da
d
c
m
atto
a
Systems of Units
0.000 000 000 000 000 001  1018

n
p
f
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Charge and Current
• Charge
– An electrical property of the atomic particles of which
matter consists, measured in coulombs (C).
• Electronic Charge
e  1.60 217733 1019 (C)
• Coulomb
– Unit for charges, 1 C charges:
1 (1.60217733 1019 )  6.24 1018 electrons
• Low of conservation of charge
– Charge can neither be created nor destroyed.
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Charge and Current
• Electric Current
– The time rate of change of charge, measured in amperes (A).
dq
i
dt
(1.1)
1 ampere
=1 coulomb / 1 second
t
Q   i dt
t0
(1.2)
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Charge and Current
• Direct Current (dc)
– A current that remains constant with time.
• Alternating Current (ac)
– A current that varies sinusoidally with time.
I
i
t
0
0
Direct current (dc)
t
Alternating current (ac)
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Charge and Current
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Example 1.1
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Practice Problem 1.1
• Calculate the amount of charge represented by four million
protons.
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Example 1.2
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Practice Problem 1.2
• If in Example 1.2, q = (10 – 10e–2t ) mC, find the current at
t = 0.5 s.
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Example 1.3
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Practice Problem 1.3
• The current flowing through an element is
 2 A, 0  t  1
i 2
t 1
2t A,
Calculate the charge entering the element from t = 0 to t = 2s.
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Voltage
• Voltage (or Potential difference, emf)
– The energy required to move a unit charge through an
element, measured in volts (V).
dw
(1.3)
vab 
dq
vab = –vba
1 volt
= 1 joule / 1 coulomb
= 1 newton-meter / 1 coulomb
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Voltage
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Power and Energy
•
• Power
– The time rate of expending or absorbing energy, measured
in watts (W).
dw
p
(1.5)
dt
dw dw dq
p


 vi
(1.6)
dt dq dt
p  vi
(1.7)
instantaneous power
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Power and Energy
• Passive sign convention
– Current enter the positive polarity of the voltage.
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Power and Energy
• Passive sign convention
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Power and Energy
• Law of conservation of power
p0
(1.8)
• Energy
– The capacity to do work, measured in joules (J).
t
t
t0
t0
w   p dt   vi dt
(1.9)
– The electric power utility companies measure energy in
watt-hours (Wh):
1 Wh = 3600 J
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Example 1.4
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Practice Problem 1.4
• To move charge q from point a to point b requires –30 J. Find
the voltage drop vab if: (a) q = 2C, (b) q = – 6C.
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Example 1.5
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Example 1.5 (cont.)
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Practice Problem 1.5
• Find the power delivered to the element in Example 1.5 at t = 5
ms if the current remains the same but the voltage is:
(a) v = 2i V,
t
(b)
v  10  5 idt V.

0

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Example 1.6
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Practice Problem 1.6
• A stove element draws 15A when connected to a 240-V line.
How long does it take to consume 60 kJ?
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Circuit Elements
• 2 types of elements: Passive and Active
• Active elements: Voltage sources, current sources, …
• 2 kinds of sources: Independent and Dependent sources
• Ideal independent source
– An active element that provides a specified voltage or
current that is completely independent of other circuit
elements.
• Ideal dependent (or controlled) source
– An active element in which the source quantity is
controlled by another voltage or current.
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Circuit Elements
• Independent sources
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Circuit Elements
• Dependent sources
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Circuit Elements
• 4 possible types of dependent sources
– A voltage-controlled voltage source (VCVS)
– A current-controlled voltage source (CCVS)
– A voltage-controlled current source (VCCS)
– A current-controlled current source (CCCS)
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Circuit Elements
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Example 1.7
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Example 1.7 (cont.)
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Example 1.7 (cont.)
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Practice Problem 1.7
• Compute the power absorbed or supplied by each component
of the circuit in Fig. 1.16.
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Applications
• TV Picture Tube
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Example 1.8
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Example 1.8 (cont.)
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Practice Problem 1.8
• If an electron beam in a TV picture tube carries 1013 electrons/
second and is passing through plates maintained at a potential
difference of 30 kV, calculate the power in the beam.
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Applications
• Electricity Bills
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Example 1.9
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Example 1.9 (cont.)
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Practice Problem 1.9
• Referring to the residential rate schedule in Example 1.9,
calculate the average cost per kWh if only 400 kWh are
consumed in July when the family is on vacation most of the
time.
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Problem Solving
1. Carefully Define the problem.
2. Present everything you know about the problem.
3. Establish a set of Alternative solutions and determine the one
that promises the greatest likelihood of success.
4. Attempt a problem solution.
5. Evaluate the solution and check for accuracy.
6. Has the problem been solved Satisfactorily? If so, present the
solution; if not, then return to step 3 and continue through the
process again.
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Example 1.10
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Example 1.10 (cont.)
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Example 1.10 (cont.)
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Example 1.10 (cont.)
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Example 1.10 (cont.)
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