Transcript Ohm`s Law

Russo Marco 5a E
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Ohm’s Law is a Math formula that
establishes the relation between the
three main classes of electricity: the
resistance, the current and the
voltage.
There are three different ways that
are used to represent Ohm’s law.
R is the resistance which is
represented by the omega symbol.
This is the ability of a material to
restrict the flow of electrons.
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All materials have a resistance. They
can obstruct the flow of electrons or
allow them to flow freely.
In the international system the unit
of measurement of the resistance is
the ohm.
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V is Voltage which is the difference
in electrical potential between two
points.
The difference of potential among
the terminals of a circuit is the same
as the result of the resistance of this
circuit by the electric current
intensity that passes by that circuit.
Mathematically we have:
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I is the current which is the rate of the
flow of electrons in a circuit. Measured in
amperes. This is a measurement
recording in one second how many
electrons are passing a specific point.
Mathematically we have:
For the first Ohm’s law, the characteristic
curve of a metal is a straight line passing
through the origin of the axes.
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For the second ohm’s law the
resistance depends on the nature and
size of the conductor.
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He clearly defined the electric
resistance of a conductor. He himself
demonstrated that the resistance of a
conductor is directly proportional to
its length and inversely proportional to
the area of its transversal section.
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ρ = resistivity, depends on the
material of the conductor and its
temperature.
ℓ = width of the conductor.
A = area of the transversal section.
With a cylindrical conductor of length L
and transversal section A, we will see
that its electric resistance is bigger when
the length L is bigger and the section A
is smaller, and the electric resistance will
be smaller when the length L is smaller
and the section A is bigger, and also
depending on the material the conductor
is constituted through a coefficient
nominated resistivity (ρ).
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There is one more important
variable which is power. This is
expressed in watts or wattage. It is
the process in which electrical
current releases heat. There are
three different ways to calculate
wattage:
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The electric current is a result of
free electron movement. When the
electric current circulates the
particles that are in movement end
up hitting the other parts of the
conductor that are in rest, causing a
kinetic energy variation that will
generate a heating effect. This
heating effect is named Joule’s
effect. Mathematically we have:
Q = (I)²(R)(t)
Where:
I = current intensity
R = conductor resistance
t = time that the current travels the
conductor