ELECTRICAL AND ELECTRONIC ELECTRICAL AND ELECTRONIC TECHNOLOGYTECHNOLOGY

((BEX17003BEX17003) )

DR SOON CHIN FHONGDepartment of Electronic Engineering Faculty of Electrical and Electronic EngineeringUniversiti Tun Hussein Onn Malaysia

Name : DR SOON CHIN FHONG Website: http://www.chinfhong.webs.com/ Education :

B.Eng (Hons) in Electrical and Electronic Engineering (UTM)

Diploma in Education (UTM)M.Eng in Electrical and Electronic Engineering (UTM)

About me

M.Eng in Electrical and Electronic Engineering (UTM) PhD in Molecular and Biomedical Engineering

(Bradford Univ.)Contact: Email : soon@uthm.edu.my Tel : 07-4538614 (Office) Room : F5-001-03(MiNT-SRC)

Chapter 1: CHARGE AND

ELECTRICAL VARIABLES

1.1 Definitions and UnitsElectric circuit, or electric network:Electric circuit, or electric network:

- A collection of electrical elements interconnected in some way.

FIGURE 1.1: General two-terminal electrical elements

a b

Example

FIGURE 1.2: A simple electric circuit

Important terminology Coulomb (C):Coulomb (C):

- The basic unit used to measure electric charge

Joule (J):Joule (J):- A joule is the work done by a constant 1-N force - A joule is the work done by a constant 1-N force

applied through a 1-m distance.(1Nm = 1 J)

Ampere (A):Ampere (A):- One ampere or amp is the current that flows when 1

Coulomb of charge passes each second (1 A = 1 C/s)

Cont Volt (V):Volt (V):

- If a charge of 1 Coulomb may be moved between two points in space with expenditure of 1 Joule of work, 1 Volt is said to be a potential difference existing between these points (1 V = 1 J/C)

Watt (W):Watt (W):- The rate at which work is done or energy

expended. The watt is defined as 1 Joule per second (1W =1 J/s).

Quantities and SI Units

Quantities and SI Units:Quantities and SI Units:- The International System of Units (SI) will be

used throughout this course.used throughout this course.- The standard language for measurement- 6 principal units

The six basic SI unitsTABLE 1.1: The six basic SI Units

QUANTITY BASIC UNIT SYMBOL

Length meter mMass kilogram kgMass kilogram kgTime second sElectric current ampere AThermodynamic temperature kelvin KLuminous intensity candela cd

TABLE 1.2: Prefixes in the SI

Prefixes in the SI

MULTIPLIER PREFIXES SYMBOL1012 Tera T

1009 Giga G1006 Mega M1006 Mega M1003 (=1000) Kilo k10-03 (=1/1000 =0.001) Mili m10-06 Micro

10-09 Nano n

10-12 Pico p

Example 1.1a. Convert 0.15mA (0.15mA) to

microamperes (A)

Solution:Solution:0.15mA = 0.15x10-3A

= 150 x 10-6A= 150 A

b. Add 15mA and 8000A and express the sum in mA

Solution:Convert 8000A to 8mA.15x10-3 A + 8000x10-6 A= 15x10-3 A + 8x10-3 A= 15mA+8mA= 23mA

1.1 Electric Charge1.1 Electric Charge

1.2 Charge and Currents All things are made of indivisible particles called

atom.

Charge:Charge:- Is an electrical property of the atomic particles of

which matter consist, measured in Coulomb (C).

ContEach atom consists of electrons, protons and neutrons.

- 1 electron charge,e= -1.602 x 10-19C- 1 proton charge,e= 1.602 x 10-19C

--

-

FIGURE 1.3: Electrons flow

- -

-

-

-

-

-

-

-

-

+ -

unlike charges attract AND like charges repel

1.2 Current and 1.2 Current and Voltage

Electric current

Electric current:Electric current:- Electric current is the time rate of

change of charge, measured in amperes change of charge, measured in amperes (A).

- Motion of chargers creates electric current.

Cont

I

FIGURE 1.4: Electric current due to flow of electronic charge in a conductor

Battery

Mathematically:Mathematically:The relationship between current i, charge q, and time t, is

dq

Cont

dtdqi =

(Eq. 1.1)

where current is measured in amperes (A), and1 ampere = 1 coulomb/second

The charge transferred between time to and t is obtained by integrating both sides of Eq. (1).We obtain,

=t

idtq

Cont

=to

idtq

(Eq. 1.2)i = dq/dt;

tt0 (dq/dt) dt = tt0 i dt

A direct current (dc) is a current that remains constant with time.

An alternating current (ac) is a current that varies sinusoidally with time.

FIGURE 1.5: Two common types of current: (a) direct current (dc), (b) alternating current (ac).

Example 1.21. Given:-

(a) i(t) = (3t2 - t) A. Calculate charge,q from t=1 to t=2 s.

Answer:q = idt = (3t2 - t) dt

= [t3 - t2/2] from 1 to 2 sec= (8-2) (1- 1/2) = 5.5 C

Example 1.32. How much charge (Q) is represented by 4,600 electrons?

Answer:Each electron has -1.602 x 10-19C. Each electron has -1.602 x 10 C. Hence 4,600 electrons will have

-1.602 x 10-19 C/electron x 4,600 electrons

= -7.369 x 10-16 C

VoltageVoltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts (V) and is define as energy of work (W) define as energy of work (W) per unit charge (Q).

V=W/Q

Where W is expressed in joules (J) and Q is in columbs (C).

FIGURE 1.6:Polarity of voltage Vab

Example 1.4

If 50J of energy are available for every 10C of charge, what is the voltage?

V= W/Q=50J/10C=50J/10C=5V

1.3 Independent and Dependent SourceDependent Source

Independent Source An ideal independent source is an active element that

provides a specified voltage or current that is completely independent of other circuit variables.

FIGURE 1.8: Symbols for independent voltage sources:(a)used for constant or time-varying voltage,

(b)used for constant voltage (dc).

FIGURE 1.9:Symbol for

independent current source.

Dependent SourceAn ideal dependent (or controlled) source is an active element in which the source quantity is controlled by another voltage or current.

Fig 1.10: Symbols for a) dependent voltage sources b) dependentcurrent sources

1.4 Basic Ideal Circuit elementselements

Circuit Elements

An element is the basic building block of circuit.

An electric circuit is simply an interconnection of the elements.of the elements.

Circuit analysis is the process of determining voltages across (or the currents through) the elements of the circuit.

There are two types of elements found in electric circuits: passive elements and active elements.

ContAn active element is capable of generating

energy while apassive element is not.

Active element Typical active elements include generators, Typical active elements include generators,

batteries, and operational amplifiers. The most important active elements are

voltage or current sources that generally deliver power to the circuit connected to them.

Passive element Examples of passive elements are resistors,

capacitors, and inductors.

1.5 Power and Energy1.5 Power and Energy

Power Power is the time rate of expending or absorbing

energy, measured in watts (W). There is always a certain amount of power dissipated in electrical circuit, depend on amount of resistance and current, as express as:

P =I2RP =I2R

P = I(IR)= IV

P = IV= (V/R)V= V2R .

Equation 1

Equation 2

Equation 3

= 3A

= 4V

= - 3A

p = vi = 4 x 3 = 12 W p = v ( -i) = 4 x (- 3 ) = -12 W

Figure 1.7 (a) : Element with absorbing power of 12 W

Figure 1.7 (b) : Element with Supplying power of 12 W

How to make Rochelle salt piezoelectric crystals Element of supplying power http://www.youtube.com/watch?v=E1Ct3V

UWvhQUWvhQ

Energy is ability to do work. Power is the rate at which energy is used.

Power, symbolized by P, is certain amount of energy, symbolized by W, used in certain length of time (t), expressed as below:

Energy

of time (t), expressed as below:P= W

t

Energy is measured in joules (J), time t is measured in seconds (s) and power P is measured in watts (W).

Example 1.5

What is power in watts for an amount of energy equal to 100J used in 5 s?

Solution:P= W/t

= 100J/5s= 20W