electronics 1 introduction

7/23/2019 Electronics 1 Introduction

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electricity

a phenomenon associatedwith the presence andmotion of electrons andother charged particles


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electric current

the directional motion ofelectrons


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electrostatics

deals with stationarycharged particles


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magnetism

the effect of movingelectrons


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electromagnetism

magnetism due to electriccurrent


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atomic structure

Electrons are present in every

material and its motions are

usually illustrated together with

protons and neutrons within an

atomic structure.


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John Joseph Thomson (1856-1940)

discovered the electron in 1897,

which he initially called

corpuscles, meaning a living cell


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elementary particles

Electronsnegatively charged

particles

Protonspositively charged

particles

Neutronselectrically neutral (nocharge)

Mass of proton1836 times the

mass of electron


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elementary particles

Particle Charge, C Mass, kg Charge to

mass ratio,

C/kg

Electron

Proton

Neutron none N/A


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structure of matter

The elementary particles are

basic form of matter and as they

combine they form another

matter, the atom; and as atoms

combine forms yet another

different matter.


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structure of matter

Matteranything in the universe

that has mass, occupies space,

and is convertible to energy

Atoma substance consisting of

the basic particles, electrons,protons, and neutrons. As atoms

combine they form either an

element or a compound


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structure of matter

Elementsubstance consisting of

atoms of only one kind. This is

considered as the elementary

(irreducible) chemical identity of

materials

Compounda combination of two

or more different atoms or

elements. Most of the insulators

are compound


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structure of matter

Moleculethe smallest part of a

compound or material that retains

all the properties of the compound

Atomic numberrepresents the

number of protons in the nucleusof an atom which in a neutral

atom equals the number of

electrons outside the nucleus.

This number determines the place

of the element in the periodic

table of elements


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Niel Henrik David Bohr (1885-1962)

the Danish physicist who

developed a new model of atomic

structure called the Bohr Atomic

Model in 1913.


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Bohr atomic model

The maximum number of

electrons (e-) that can occupy a

given shell or the nthshell can be

approximated by:

where: n is the nthshell


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Bohr atomic model

Energy levelthe farther the

electron from the nucleus, the

higher its energy level

Valence shellthe outermost

shell or the last shell. This shell ororbit is filled with the remaining

electrons.


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Bohr atomic model

Valence electronselectrons that

occupies the valence shell or the

last shell

Free electronsoriginally valence

electrons. As they gain enoughenergy they escape from the

valence shell and become free.


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electrical classifications of material

The number of valence electrons

is a common indication that tells

us the electrical characteristics of

a material


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conductor

material with less than four

valence electrons; allows

electrical current to flow easily

because they have more free

electrons


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insulator

material with more than four

valence electrons; will not allow

electrical current to flow easily

because they have very few or

even no free electrons


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semiconductor

with exactly four valence

electrons; have electrical

characteristics in between

conductors and insulators


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energy bands

Before a valence electron can

escape from its shell and

becomes free, it must gain energy

of at least equal to the energy

gap.


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energy gap

the energy difference between

the valence band and conduction

band. Its unit is the electron volt

(eV)


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valence band

the region where the valence

shell and valence electrons are

occupying. It is the highest energy

level before conduction band


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conduction band

the region where free electrons

are said to be present. Electrons

at this band have a higher energy

level than those electrons at the

valence band.


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forbidden band

the region in an atom where no

electrons exist. It is in between

two allowed bands, such as

between valence and conduction

bands.


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electron volt

a unit of energy equal to the

energy gained by an electron in

passing from a point of low

potential to a point one volt higher

in potential


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energy gap of different materials

Means that the valence electrons

can easily become free. This

explains why conductors have the

most number of free electrons

and can easily support electric

current flow


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electric charge (Q)

a fundamental property of

matter and is influenced by

elementary particles such as

electrons and protons


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kinds of electric charges

Positive chargecarried by

protons

Negative chargecarried by

electrons


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coulomb (C)

unit of electric charge; named

after the French physicist, Charles

Augustin de Coulomb (1736-

1806)


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conservation of charge

the total or net electric charge in

an isolated system always

remains constant


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conservation of charge-energy

electric charge is neither

created nor destroyed but is

transferred from one body to

another


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charged atom and charged body

Basically, atoms are electrically

neutral (balance) which means

the number of negatively charged

electrons and the number of

positively charged protons are

equal. This is uncharged atomand the material whose atoms are

uncharged is called uncharged

body.


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ions

Anionnegatively charged ion

Cationpositively charged ion


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cation

Atom that loses electron lacks

negative charge and the atom

becomes positively charged ion,

cation.

Electropositive elements

elements that give up electrons in

chemical reactions to produce

positive ions. These elements are

metallic in nature.


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anion

Atom that gains electron will have

more negative charge and the

atom becomes negatively charge

ion, anion.

Electronegative elements

elements that accept electrons in

chemical reactions to produce

negative ions. These elements

are nonmetallic in nature.


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electric field and electric force

When the body is electrically

charged, it is said to have electric

field in its surroundings. This field

interacts with other charged

bodies and will produce an

electric force that may causethem to move.


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electric field and electric force

Electric fieldthe area or region

surrounding an electrically

charged particle or body

Electric forcethe force

produced due to the electric field

of a charged particle or body


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electrical potential

the ability of a charged body to

do work on charged particles such

as electrons.

The fact that charged bodies tendto move charged particles, it is

said to have a capacity to do work

or it has a potential to do work.

This is also called electrical

potential energy.


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Electrical potential difference

the difference between the

capacities (potentials) of two

charges to do work

Voltthe unit of potential

difference. A potential of one volt

has the capacity to do one joule of

work in moving one coulomb of

charge; named after the Italian

physicist, Alessandro Volta (1745-

1827) in 1881.


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Voltageanother name of

potential difference expressed in

volts

Electromotive force (EMF)the

electrical force that moves the

charged particles such as

electrons (electron moving force).

The term emf is used

interchangeably with potential

difference and voltage


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Count Volta

Count Alessandro Giuseppe

Antonio Anastasio Volta invented

the voltaic pile, the first electric

cell, in 1796. Using his voltaic

pile, he produced a continuous

electric current for the first time onearth.


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electric current

any directional movement of

electric charges such as electrons


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electric current

Current in gases and liquids

generally consists of a flow of

positive ions in one direction

together with a flow of negativeions in the opposite direction


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ampere

the unit of electric current.

Current of one ampere is equal to

one coulomb of charge flows a

given point in one second; named

after French physicist and

mathematician Andre M. Ampere(1775-1836)


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current

Direct currentcharges flow in

one direction only

Alternating currentthe motion of

electric charges is periodically

reversed

Conventional currentthe

assumption which considered the

flow of charge from positive to

negative. This is opposite to the

actual charge flow negative to

positive


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material resistance

the ability of a material to

oppose or block the flow of

charge or current


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electrostatics

deals with phenomena due to

attractions or repulsions of electric

charges that are not moving.


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properties of electric force

According to Charles Augustin de

Coulomb (1736-1806) French

physicist, the electric force for

charges at rest has the following

properties:

1. The size of the force of

attraction or repulsion between

two charges is directly

proportional to the value of each

charge (Coulombs first law of

electrostatics)


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properties of electric force

2. The size of the force variesinversely as the square of the

distance between the two

charges (Coulombs second law

of electrostatics)

3. The attraction or repulsion actsalong the line between the two

charges

4. Like charges repel each other,

unlike charges attract. Thus, two

negative charges repel oneanother, while a positive charge

attracts a negative attracts a

negative charge


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Coulombs law

Coulombs law or Law of

Electrostatics

The force F between two

electrical charges is directly

proportional to the product of the

charges and inversely

proportional to the square of the

distance between them. This is

the sum of Coulombs first and

second laws.


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The end!!

electronics 1 introduction

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