Download - 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
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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electrical potential
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!!