Natural Science Project
Transcript of Natural Science Project
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Natural Science
FES 150
Lecturer:Mr. Ayman Abulail
Electric Charge and Electric Currents
Prepared by:
Ahmed Mohammed Al Sayari 200910383
Hassan Abaas Al Bloushi 2009
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Table of Contents
Table of Contents ........................................................2
Abstract .......................................................................2
Introduction .................................................................3
Charles-Augustin de Coulomb was born on 14 June
1736 in Angoulême, France. His father Henri
Coulomb, was an inspector of the Royal Fields in Montpellier. His mother, Catherine Bajet, came from
a wealthy family in the wool trade. He is best known
for developing Coulomb's law and The SI unit of
charge, the coulomb, was named after him. He did
on 23 August 1806...................................................9
Conclusion .................................................................15
Abstract
What is electricity? Where does is come from? Who
discovered it? What is it? These are some questions
that people usually don’t think about these days. Youturn on a switch and the light comes on; you put your
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keys in the ignition and turn the car turn on. These
things are some of the things we should think of and
understand what is happening behind that switch or in
the battery of the car or mobile phones, computer andall electric devices. We hear about positive and
negative charge but do not understand them and how
we use them and where they come from. Sometimes
you feel a shock when touching a door knob or while
shaking another person’s hand. What is that shock you
felt and why and how is it happening. We use the units
of Ohm and coulombs but where did these come from
and what do they represent in the world of physicsand electronics. We have many materials with
different properties. Each material has something
special that makes it different from other materials. In
electricity there are special materials that are used in
wires and other electrical devices. Why we use these
material and not other materials is a question in
addition to the pervious questions that need to beanswered.
Introduction
Electric charge and electric currents are very
important to our lives today. In the case of electric
charge we will discuss the different charges and howthey are formed. In addition to static electricity which
talks about the repletion and attraction factor of
charges and signs. Coulombs law and the discovery of
this formula that discusses the forces exerted on an
electric charge and the magnitude of these forces.
These are very important because without these we
would have faced many problems and couldn’tdevelopment and enhance our technology.
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Furthermore electric current has a major role in or
lives. We find current in all of your wires and electrical
devices. Some of the factors in electric current are the
electric battery and how it works, Ohm’s law and therelation of the voltage and resistance to the current. In
addition to resistivity and the different materials used
for electric current. These are other factors are some
greatest discoveries in the world which opened new
doors of technology and inventions. The topic is
interesting because it talks about things that all
people use everyday but don’t really understand the
physics behind it. These discoveries and factors havebeen discovered many years before and since that
time people were trying to develop and enhance these
factors to become more efficient and reliable. Some of
these factors are still being used as it was first
discovered and formulated many years ago such as
Ohm’s law and Coulombs law.
Electric Charge
Static Electricity: Electric Charge and its Conversation
Static electricity is one of the major discovers that
people found out about by coincidence. It was first
known as the “amber effect”, in which the ancient
knew that by rubbing a piece of amber tree with a
cloth, makes the amber attract small pieces of leaves.
We can also feel this even now in our daily lives such
as the attraction we feel when getting out clothes
from the dryer. Even sometimes we feel a shock when
touching a metal door knob. These are all caused as aresult of rubbing in which objects get charged and is
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then said to be a net electric charge. After some
experiments we found out that their where different
charges. One of these experiments is the plastic and
glass experiment. They rub both of these objects will asilk to charge them. Then we try charging another
glass in the same way and bring it close to the first
glass they repelled each other. But when the glass is
brought next to the plastic they attracted. This
experiment is illustrated below:
They found that there are only two kinds of electric
charges and came up with a law that states that:
unlike charges attract and like charges repel.
The charges were referred to as negative and
positive by philosopher and scientist Benjamin
Franklin. He said “that when ever a certain amount of
charge is produced on one object, an equal amount of
the opposite type of charge is produced on another
object.” “For example, when a plastic ruler is rubbed
with a paper towel, the plastic acquires a negative
charge and the towel acquires an equal amount of
positive charge. The charges are separated, but the
sum of the two is zero.” By this example we
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established what we know today as the law of
conservation of electric charge which states that the
net amount of electric charge produced in any process
is zero.
Insulators and Conductors
After many experiments we found out that there
are some materials that let electricity or electric
charges to flow and some do not allow. One of these
experiments are having two object in which one of them is charge and the another is neural (having no
charge) and having some kind of metal touching both
objects, the neural object will be charged with the
same charge as the first object. In the same conditions
instead of using a metal object to touch both objects
we use a wooden object the result will be neural and
nothing will happen to either objects. After manyexperiments we found out that materials that contain
iron are conductors (allow electric flow) and materials
such as wood and rubber are insulators (do not allow
electric flow). There are also some materials that are
not really good conductors nor are good insulators and
are not considered neither insulators nor conductors
such as silicon and germanium, these materials are
known as semiconductors.
Induced charge
An object having as positive charge is brought
close to a neutral object. When both of them touch the
neural will acquire a positive charge, meaning that the
free electrons moved from one object to the other.
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This type of charging is called charging by conduction.
Another kind of charging objects is induced charge, for
example let us take the example before with the two
rods one with a positive charge and the other with aneutral charge. If we put the positive charged rod on
one end of the neural rod without touching, the free
electrons will not be able to leave the rod, but still be
able to move within the rod. Meaning it will form a
positive charge on the opposite side of the rod which
is far from the originally positive rod which is brought
close.
An electroscope is a deviceused to detect charge. In theelectroscope there is inside twomovable metal leaves. Theseleaves are connected to a metal
knob from the outside. Theapparatus works in two ways byusing conduction and inductioncharging methods. If a positivecharge is brought close to the knobwe will be using induction chargewhich will form a positive chargeon both leaves making them repeleach other. In the other case of conduction if a positive charge
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object touches the knob the whole apparatus acquiresthe net charge, making the leaves repel. The strongerthe charge the further apart they move.
By using the electroscopewe can only know if there is a
charge in the object but still we
do not know what charge is it a
negative or a positive charge,
as illustrated before if we use a
negative charge instead of a
positive we will still get the
same result. But we can figure
out the charge using the electroscope by using this
technique. First by using conduction there was a
negative charge in the apparatus, we bring a negative
object to the knob making the charges repel and move
apart even more, then bring another object which we
know is positively charged and touch the knob if the
leaves move a but closer than before then the originalsign was negative, this technique works either way for
positive or negative charges.
Coulombs Law
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Charles-Augustin de Coulomb was
born on 14 June 1736 in
Angoulême, France. His father
Henri Coulomb, was aninspector of the Royal Fields in
Montpellier. His mother,
Catherine Bajet, came from a
wealthy family in the wool
trade. He is best known for developing Coulomb's
law and The SI unit of charge, the coulomb, was
named after him. He did on 23 August 1806.
He studied the electric charge forces of attraction and
repulsion on other electric charges and wanted to
know the factors that affected the magnitude of these
forces. Then after many studies and experiments he
came up with this statement “the force one small
charged object exerts on a second one is proportional
to the product of the magnitude of the charge on one,
Q1 times the magnitude of the charge on the other,
Q2, and inversely proportional to the square of the
distance r between them”. This is illustrated in the
equation below:
This equation as mentioned before gives the
magnitude of the electric force that either object
exerts on the other. Furthermore the direction of the
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electric force is always along the line joining the two
objects.
Electric Currents
Electric Battery
The people who discovered the electric battery were
Luigi galvanic and Volta. A battery
produces its energy by converting or
transforming chemical energy into
electrical energy this is the basic
phenomena of how it works. Today
we have many kinds of batteries and
electric cells. The basic battery
contains two rods made out of
dissimilar metals called electrodes. These electrodes are put in a
solution such as a dilute acid called
an
electrolyte. Such devices are called an electric cell and
having several cells together is considered to be a
battery.
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As shown in the figure we have two electrodes, one
made of Zinc and the other from Copper. They are
both put in sulfuric acid as the electrolyte. Theremaining part that is not in the solution is known as
the terminal where connections and wires are
connected. In this case the zinc electrode will start to
dissolve and then acquires a negative charge and the
copper gets a positive charge. If the electrodes are not
connected there will not be much flow in the cell which
will cause it to die.
Electric Current
For a battery to do its main
function and we need a
continuous path which connects
between the terminals of thebattery. This path then is
known as an electric circuit. We
use this in a light bulb, heater,
radio and many other things. In this case were we
have a continuous circuit from one terminal of the
battery to the other, the flow of charge in the wires is
called an electric current.
The current (I) is known as the amount of the charge
that passes through the conductor at any location
during the time interval as shown below:
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Electric current is measured in coulombs per second
known as Ampere, after the French physicist Andre
Ampere.
Ohm’s Law: Resistance and Resistors
This law was established by George Simon Ohm in
which he ran experiments to show that current in a
wire is proportional to the potential difference. To
have an electric current, a difference in potential is
required. Different steps and discoveries took place to
come up with Ohm’s law. The main comparison wasbetween electric current in a wire and water in a river
which is now known as the water analogy. In the end
George discovered that how small or large a current is
in a wire does not only depend on the voltage but also
on the resistance the wire offers to the flow of
electrons. This is how he came up with this equation
for the electrical resistance showing that the current isinversely proportional to the resistance.
Furthermore from that equation before he derived
what we know now as Ohm’s law, he found out that in
metal conductors the resistance is a constant
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independent of the voltage and came up with this
formula.
The unit for resistance is called ohm and is
abbreviated by omega (Ω).
Resistors are used to control the amount of current.
These resistors have resistance from less than 1 Ohm
to million of Ohms. The value of a resistance is givenor written on the resistor from the exterior, or may be
given as a color code as shown in the bottom table.
The first two colors represent the first and second
digits, the third color represents the power of ten that
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it must be multiplied by, and the fourth is the
manufactured tolerance.
Resistivity
By experiments it was found that the resistance R of
any wire is directly proportional to the length L and
inversely proportional to its cross-sectional area A.
This is how we came up with this rule.
The unit for resistivity is (Ω.m). The resistivity depends
on the material used in the first place then other
factors effect its result such as purity, heat treatment,
temperature and other factors as shown in some of
the materials below.
Discussion
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Electric factors such as electric charge, field, potential,
and current. These discoveries have led to even major
discoveries and developments that we see today. By
using Ohm’s & Coulombs law and understanding theelectric current, electric battery, the different charges
and materials. The derivation of different equations
and formulas to be able to understand the relation
between them such as Current, voltage and resistance
in Ohm’s law and how each one is inversely or directly
proportional to one another.
Conclusion
The discoveries that were mentioned before in the
field of electric charge and electric current have
changed the world as we now it today. With out these
discoveries we wouldn’t have all of this technology
and some of the luxuries we use in our daily lives.Electricity, mobile phones, computers, cars and many
other devices wouldn’t be available nowadays if not
for these discoveries. We should try to improve in the
fields of electric charge and electric current and try to
enhance them to be more efficient to provide a better
living for the future. These discoveries made by
coulomb or ohm and other scientist we found many
years ago. As the years passed the technology andusage of these discoveries have increased rapidly in
addition to having major improvement done to them
and are used in many different fields. This is how
important these finding over the years have affected
our lives as we know now it.
Reference
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DOUGLAS.C.GIANCOLI. PHYSICS: PRINCIPLES WITH APPLICATION, SIXTH
EDITION; Published by: PEARSON EDUCATION, INC: 2005.
http://www.wikipedia.org/
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