Transcript electric fluid.

ELECTRICITY and
MAGNETISM
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Several thousand years ago, the ancient Greeks
observed that a substance called amber attracted bits
of lightweight material, such as feathers or straw.
AMBER is a good electric insulator, so it easily holds
electric charge, they were actually experimenting with
static electricity when they rubbed amber. The Greek
word for amber is elektron.
Other people, including the ancient Greek and
Chinese, knew of another substance that could attract
things. It was a black rock called lodestone or
magnetic.
EARLY E
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Girolamo Cardano an Italian Mathematician in 1551 , realized that
the attracting effects of amber and of magnetite must be different.
Cardano was the first to note the difference between electricity and
magnetism.
In 1600, the English physician William Gilbert reported that such
materials as glass, sulfur and wax behaved like amber. When rubbed
with cloth, they too attracted light objects. Gilbert called these as
electrics. He studied the behavior of electrics and concluded that the
effects must be due to some kinds of fluid.
In 1730, the French scientist Charles Dufany found that the charge
pieces of glass attracted amberlike substances but repelled other
glasslike substances. Dufany decided to have 2 Kinds of Electricity.
He called one vitreous and the other resinous. He thought of them as
two kinds of “electric fluid.”
E ATTRACT AND E-REPEL
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The American scientist and statesman Benjamin Franklin
began to experiment with electricity in 1746. Franklin thought
that there is only one electric fluid. He theorized that objects
with too much fluid would repel each other but they will attract
if there are less fluid. His ideas explained how opposite charges
cancel each other out when they come in contact.
He used the term positiive for what he thought was an excess
of fluid and he used the negative for a deficiency fluid. He did
not know that electricity is not a fluid. Rather, electricity is
associated with the charges of electrons and protons.
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In 1767, the English scientist Joseph Priestley described the
mathematical law that shows how attraction weakens as the
distance between oppositely charged objects increases.
In 1785, the French scientist Charles Augustin de Coulomb
confirmed Priestley’s law. Coulomb showed that the law also
held true for the repulsive force between objects with the same
charge.
In 1771, Luigi Galvan, found that the leg of a recently killed frog
would twitch when touched with two different metals at the
same time.
In the late 1790’s Alessandro Volta showed that chemical
action occurs in a moist material in a contact with two different
metals. Volta gathered pairs of disks, consisting of one silver
and one zinc disk. Then Volta constructed the first battery
called a voltaic pale.
E-M & E-M (ELECTROMAGNETISM EXPLAINED
MATHEMATICALLY)
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The Danish physicist Hans C. Oersted found that an electric
current flowing near a compass needle would cause the needle
to move. He is the first to show a definite connectin between
electricity and magnetism.
During 1820, Andre Ampere discovered the relationship
between currents and magnetic fields called Ampere’s Law, it is
one of the basic laws of electromagnetism.
The physicist James Maxwell combined all the known laws
covering electricity and magnetism into a single set of 4
equations.
In later 1880’s Heinrich Hertz showed how to generate and
detect radio waves, transmitted electromagnetic waves and
satellite communication.
THE ELECTRONIC AGE
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The Irish physicist G. Stoney believed that electric current was
actually the movement of extremely small electriically charged
particles called electrons.
In the late 1880’s, scientists discovered that electrons can be
dislodged from metal surface in a vacuum tube. Vacuum tube
contains electrodes with wires that extended through the glass.
In 1947, Bardeen, Brattain and Shockley invented the
transistor. Transistors do the same job as vacuum tubees but
they are smaller and more durable and they use less energy.
RECENT DEVELOPMENTS
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Most of the electric energy we use comes from power pplants
that burn fossil fuels, such as coal, oil and natural gas. Some
electric energy comes from nuclear and hydroelectric plants.
Many people are concerned that the earth’s supply of fossil
fuel is limited and will someday run out. Another problem is
that the present methods of generation electric energy may
harm the environment.
Many scientists hope that new electric devices will actually help
curb the growing demand for electric energy. Computers, for
example, can control the lights, air conditioning and heating the
buildings to reduce energy use. Compact fluorescent lamps,
using miniature electronic circuits , provide the same light as
ordinary light bulbs but use only one-fifth as much electric
energy.
ELECTROSTATIC INDUCTION
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The electric charges can be redistributed by induction. If a
negatively charged object is placed near a surface that
conducts charges, the electrons on the sphere will move away
from the object. On the other hand, the positive charges on the
sphere will be attracted toward the oppositely charged object.
An electroscope is two thin gold leaves hanging from a stem in
an insulated jar and lid. Insulators are materials, such as cloth,
some plastics, glass and oil that tend to prevent charges from
moving. This is an instrument which can confirm when you
have built up static charge.