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Fundamentals of Electrical
Engineering
Lecture 1
Introduction
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Electrical Engineering
Electrical engineering is the professionconcerned with systems that produce,transmit and measure electric signals.
Five major classifications Communication systems
Computer Systems
Control Systems Power Systems
Signal Processing Systems
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Electrical Engineering (cont.)
Considerable interaction takes place among
the engineering disciplines involved in
designing and operating.
A good example of the interaction among
systems is commercial airplane.
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Charge
The unit charge is the coulomb (C) where onecoulomb is one ampere second.
The coulomb is defined as the quantity of
electricity that flows past a given point in anelectric circuit when a current of one ampereis maintained for one second
= Where I is the current in amperes and t is the
time in seconds.
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Example
If a current of 5A flows for 2 minutes, find the
quantity of electricity transferred?
Solution
Quantity of Electricity = coulombs
I = 5 A, t = 2 X 60 = 120s
Hence, Q = 5 x 120 = 600 C
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Electric Charge
Physical property of matter that causes it to
experience a force when near other
electrically charged matter.
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SI Units
Systme International dUnits (International
systems of units)
Basic SI units
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Quantity Unit
Length Meter, m
Mass Kilogram, Kg
Time Second, s
Electric current Ampere, A
Thermodynamic temperature Kelvin, K
Luminous intensity Candela, cd
Amount of substance Mole, mol
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SI Units (cont.)
Derived SI units
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Quantity Unit Name Formula
Frequency Hertz (Hz)
Force Newton (N) . /
Energy or work Joule (J) .
Power Watt (W) /
Electric charge Coulomb (C) .
Electric potential Volt (V) /Electric resistance Ohm () /
Electric capacitance Farad (F) /
Magnetic flux Weber (Wb) .
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SI Units (cont.)
PREFIX SYMBOL POWER
Pico p 10
Nano n 109
Micro 106
Milli m 103
Centi c 10
Kilo k 103
Mega M 106
Giga G 109
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Force
A force is any influence that causes an object
to undergo a certain change, either
concerning its movement, direction, or
geometrical construction.
From Newtons second law of motion
=
F is force, m is mass and a is acceleration.
Unit of force is newton (N).
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Example
A mass of 5000 g is accelerated at 2 /by a
force. Determine the force needed.
Solution
=
= 5 2
= 10
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Work
Distance covered in the direction of applied
force.
=
Unit of work is joule (J), where one joule is
one Newton meter.
Energy is capacity of a body to do work.
Different kinds of energy.
Law of conservation of energy.
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Power
Rate of doing work or transferring energy
=
The unit of power is watt (W), where one watt
is one joule per second.
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Example
1. A portable machine requires a force of 200 N
to move it. How much work is done if the
machine is moved 20 m and what average
power is utilized if the movement takes 25 s?
2. A mass of 1000 kg is raised through a height
of 10 m in 20 s. What is (a) the work done
and (b) the power developed?
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