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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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