lect01 electrical quantities and laws electrical eng for mech 802307
TRANSCRIPT
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802307
ELECTRICAL ENGINEERING FORMECHANICAL ENGINEER
Tarek M. Abdolkader
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• Description of
the
course
• Fundamental electrical quantities and laws
لعربية لسعوديلمملكة
جامعة م لقر-وز رة لتعليم لعالي
كلية لهندسة و لعمارة إلسالمية
قسم لهندسة لكهربائية
802307: ELECTRICAL ENGINEERING
FOR MECHANICAL ENGINEER
K INGDOM OF SAUDI ARABIA
Ministry of Higher Education
Umm Al-Qura University
College of Engineering and Islamic ArchitectureElectrical Engineering Department
Lecture
1
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OUTLINE
• Description of the course• Course outline
• Notices
• Grading policy
• Do we need Electrical Engineering?
• Fundamental
electrical
quantities
and
laws• Charge• Current
• Voltage
• Power
and
energy
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Presentation slides: (not adequate alone)
Lecture notes
Textbook:
John Bird, Electrical and Electronic principles and Technology , 2nd Ed., Newnes,
2003.
References:
1. Hughes, “Electrical technology,” 7th Ed., Addison‐Wesley, 1995.
2. A.E. Fitzgerald,
“Basic
electrical
engineering,”
McGraw
‐Hill.
3. T. A.DeMassa,“Electrical and Electronic Devices Circuits and Instruments,” West
Publishing Company, St. Paul, 1989.
4. P.J. Freeman, “Electric power transmission and distribution,” 2nd Ed., Harrap
Resources
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1. Attendance of lectures is a must.
2. Ask whenever you feel any ambiguity or confusion.
3. You have to read the text book along with lecture notes and presentation slides.
4. Solving a lot
of
examples
and
exercises
is
a must
to
get
the
skills
needed
to
pass
this
course.
لنصيح لنصيحلين لنصيحلين لنصيحلين لنصيحلين لنصيحلين لنصيحلين لنصيحلين لنصيحلين لين
Notices
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Semester works
40
Attendence
5
0.5 grades are subtracted for each one hour
absence in either lecture or Lab. Absence
more than 25% of hours of the course
(lecture and/or Lab) leads to Denial.Homeworks (HWs)
10
HWs given in lecture are due before the next
lecture. To take the grades of HW, you must
come to office hours to discuss solution with
the instructor.
Quizzes
10
Two Quizzes are given with 5 grades each.
The first Quiz is after the 4rd week and thesecond Quiz is after the 10th week
Midterm
15
Midterm exam should be after the 7 th week
Lab
20
Lab semester work
10
For each experiment, a report to be
submitted
Final lab exam
10
After the 13th week.
Final exam
40 No curve up
Semester works 40%
Lab 20%Final Exam 40%
Grading Policy
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You need Electrical Engineering
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You need Electrical Engineering
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Charge
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Current
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Current
A constant current (also known
as a direct current or DC) is
denoted by symbol I whereas a
time-varying current (alsoknown as alternating current or
AC) is represented by the
symbol i or i(t )
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If a current of 5 A flows for 2 minutes, find the quantityof electricity transferred.
See Problem 1 at p. 4 in the textbook
Q
= 600 C
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The total charge passing through a conductor is given by:
5 sin(4 )q t t mC π =
Calculate the
electric
current
at
t =
0.5
s
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Determine the total charge entering a terminal between t = 1 sand t = 2 s if the current passing the terminal is defined by:
i = (3
t 2
– t
) A
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Voltage
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VoltageMathematically,
ab
dwv
dq
=
Where v is in volts (V), w is energy in joules (J), and q is charge in Coulombs
(C)
1 volt = 1 joule/coulomb
Like electric current, a constant voltage is called a DC voltage and it is
represented by V, whereas a sinusoidal time-varying voltage is called a AC
voltage and is represented by v. The electromotive force (e.m.f) provided by a
source of energy such as a battery (DC voltage) or an electric generator (ACvoltage) is measured in volts
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Power and Energy
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Power and EnergyWe write the relationship as:
dw p
dt =
Where p is the power in Watts, w is the energy in joules (J), and time in
seconds. From voltage and current equations, it follows that:
dw dw dq p vi
dt dq dt = = =
p is the
instantaneous
power
and
is
equal
to
the
product
of
instantaneous
voltage and current
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• Due to the conservation of energy,
The algebraic sum of power in a circuit, at any instant of time, must be zero
0 p =∑• In another form,
The total power supplied = the total power absorbed
The supplied by the source = VI
The power absorbed by the resistor = VI
Power and Energy
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A source of e.m.f of 5 V supplies a current 3 A for 10 minutes.How much energy is provided in this time?
See Problem 7 at p. 6 in the textbook
Energy = 9 kJ
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An electric heater consumes 1.8 MJ when connected to a 250 Vsupply for 30 minutes. Find the power rating of the heater andthe current taken from the supply.
See Problem 8 at p. 6 in the textbook
Power = 1 kW
Current = 4 A
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An air conditioner of 3 kW power. How does it cost per month tooperate this AC 10 hours per day. 1kwh costs 10 Halalah.