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8/13/2019 Chapter 1 Eee121 Introduction_hanim
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Chapter1
ntro uct on
8/13/2019 Chapter 1 Eee121 Introduction_hanim
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INTRODUCTIONLesson
Outcome:
tt een o t e esson,stu entss ou ea eto:
Definebasic
concept
of
charge,
current,
voltage,
circuit
elements,powerandenergy.
Calculatethecharge,current,voltage,powerand
energyfor
specific
circuit
elements.
Applyandrelatethebasicconceptaccordingtotheirapplication.
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Cha ter1:Introduction
.
1.2 ElectricCharge.
1.3 urren .1.4 Voltage.
1.5 PowerandEnergy.
1.6 CircuitElements.
3nsmh...
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. .The electrical and magnetic units commonly used in electricalcircuit are shown in Table 1.1 and Table 1.2.
Quantity Symbol Unit Symbol
Table 1.1: Electrical quantities
Capacitance
Charge
C
Q
Farad
Coulomb
F
C
Conductance
Current
Energy
G
I
W
Siemens
Ampere
Joule
S
A
J
Frequency
Impedance
f
Z
Hertz
Ohm
Hz
Power
Reactance
P
X
Watt
Ohm
W
Resistance
Voltage
R
V
Ohm
Volt
V
4nsmh...
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1.1.ELECTRICAL ANDMAGNETICUNITS(Cont)
Quantity Symbol Unit Symbol
a e . : agnet c quant t es
Flux density
Magnetic flux
B
Tesla
Weber
T
Wb
Magnetizing forceMagnetomotive force
Permeability
HFm
Ampere-turns/meterAmpere-turn
Webers/ampere-turns-meter
At/mAt
Wb/Atm
Reluctance Ampere-turns/weber At/Wb
5nsmh...
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1.2ElectricChar es Chargeisanelectricalpropertyoftheatomicparticlesof
whichmatterconsists,measuredincoulombs(C).
Thechargee ononeelectronisnegativeandequalin1
. charge.Thechargesthatoccurinnatureareintegral
multi les ofthe
electronic
char e.
1coulombisaunitofchargethatcontains6.24x1018electrons
6nsmh...
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1.3Current 1Electric
Current
is
the
time
rate
of
charge,
measuredinamperes(A).
Mathematicall ,therelationshi betweencurrent
i,charge
q,
and
time
tisi
=dq/dt.
The
unit
of
am erecanbederivedas1A=1C/s.
Adirectcurrent(dc)isacurrentthatremains
Analternatingcurrent(ac)isacurrentthatvaries.
7nsmh...
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1.3Current(2)
The
direction
of
current
flow
Positive ions Negative ions
8nsmh...
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1.3Current(3)Example1Aconductorhasaconstantcurrentof 5A.
Howman electrons assafixed ointontheconductorinoneminute?
9nsmh...
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1.3Current(4)o ut on
Totalno.ofchargespassin1minisgivenby
A= C/s 60s/min = 00C/min
.
minelectrons/1087.1C/electron10602.1
19
xx
10nsmh...
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1.4Voltage(1)
chargethroughanelement,measuredinvolts(V).
,
wisenergyinjoules(J)andqischargeincoulomb(C).
ab
Electricvoltage,vab,isalwaysacrossthecircuitelement orbetweentwo
ointsinacircuit.
vab>0meansthepotentialofaishigherthanpotentialof b.
vab