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Outline
Origin of Electricity
Electric Charge
Early Theories on Charges
Quantization Of Charge
Conservation of Electric Charge
The Triboelectric Series
Conductors and Insulators
Process of Charging
Electricity
filament
Switch 1
Switch 2
Lamp 1
Lamp 2
D.C.
Electricity
Direct Current
A.C.
Alternating Current
Static electricity
Static Electricity
when a material
has an excess or
a lack of
electrons.
Conductor
Something that allows
thermal energy to pass easily
Metal
Water
Insulator
Something that does
NOT allow
thermal energy
to pass easily
semi-Conductor
The Origin of Electricity
Lode stone – magnetized iron core.
Amber – a translucent yellowish- brown fossil
resin.
The first recorded investigator of such ability of
amber was Thales of Miletus ( as early as 600
B.C.) – one of the seven wise men of ancient
Greece,
William Gilbert ( 1600) – found out that many
other substances when rubbed against another
substance have this ability of amber. He called
these substances electrics which comes from the
Greek word elektron meaning “amber”. It was
shown that every object acquires this ability to
attract small pieces of matter after it was rubbed
against another.
Electric Charge
“When amber rubbed with wool, the amber
could then attract other objects”. We say that
amber has acquired a net electric charge or
has become charged.
“When you scuff your shoes across a nylon
carpet, you become electrically charged, and
you can charge a comb by passing it through
dry hair”.
Electric Charge
Glass rod rubbed
with silk
Plastic rod
rubbed with fur
There are two kinds of electric charge:
positive and negative.
The figure demonstrates that charge with
the same electrical sign repel each other,
and charges with opposite electrical signs
attract each other.
In the rubbing process, small amount of positive
charge is transferred from the silk cloth to the
glass rod, so the original neutral rod is now
positively charged.
The opposite happens when a plastic rod is
rubbed with fur.
In the above, neutral means that the total number
of positive charge is same as the total number of
negative charge in the object.
Early Theories on Charges
One fluid theory by Benjamin Franklin. According
to this theory, all bodies possess a certain amount of
“electric fluid” needed to keep them uncharged. When
two bodies are rubbed together, one of the bodies get
some of this fluid from the other body. The body that
loses some of the fluid becomes negatively charged;
the one that gains the fluid become positively charged.
Two - fluid theory by Charles Du Fay – “all bodies
contain equal amount of two kinds of fluid. When two
bodies are rubbed together, one of these fluids spreads
over one body making it positively charged, while the
other kind of fluid spreads over the other body,
making it negative charged.
Dielectric theory of James Clerk Maxwell
and Michael Faraday – consider charges as a
form of strain in the hypothetical ether
surrounding a body. To charge a body is to
strain the ether and to discharge it is to remove
this strain.
The Atomic Structure
The modern theory of electric charges is the
electron theory. It explains the existence of
charges by the structure of atom.
Atomic Structure
The number of protons and electrons are equal
and hence the atom is neutral.
An atom may gain or loses electrons under
some circumtances. If the atom gains electron,
it become negatively charged. If it loses
electrons, it becomes positively charged.
The SI unit of charge is coulomb, C.
The charge of an electron (-e) is -1.6 x 10-19 C.
The charge of proton (+e) is +1.6 x 10-19 C.
Important Facts About Proton, Neutron, and
Electron
Location
Mass
Charge
Proton
Inside Nucleus
1.6725 x 10-27 kg +1.6 x 10 -19 C
Neutron
Inside Nucleus
1.6749x 10-27 kg
None
Electron
Around Nucleus
9.1095x 10-31 kg
-1.6 x 10 -19 C
Answer :
1. How many electrons must be removed from
an object for it to have a charge of 1.0 C?
Switch 1
Switch 2
Lamp 1
Lamp 2
Electricity
filament
Electricity - electrons moving through a
metal wire.
Atomic Absorption
Atomic Emission
Magic is technology that is
not understood.
Electrical Energy - is energy
resulting from the force
between two objects having
different voltages.
Electrical Energy - is the
force of moving electrons.
Circuits
Series Parallel
Static electricity
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Static electricity
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Electricity filament
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