Transcript Pre-VisitIntrotoEner..

Tucson Solar Schools Project
Introduction
to Energy
and
Electricity
E NVI R ONM E NT AL
E D U C A T I O N
E X C H A N G E
About Energy
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In everyday language,
we use the word energy
in many ways.
In science, energy is
defined as the capacity
to do work.
Energy “Rules”
Energy is governed by natural laws that we
call the Laws of Thermodynamics.
These are among the most fundamental principles
in all of science!
First Law of Thermodynamics
Law of Conservation of Energy
Energy can be neither created nor
destroyed… but it can be changed
from one form to another.
(The total amount of energy in the
universe is constant.)
Forms of Energy
Energy occurs in many forms:
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Light
Heat
Sound
Chemical
Gravitational (energy of position)
Nuclear
Kinetic (motion or mechanical energy)
Electrical energy (electricity)
Energy Can Change Forms…
(from the First Law of Thermodynamics)
For example:
Electrical energy becomes heat energy when…
…we turn on an electric heater.
Kinetic energy becomes mechanical
energy when…
…moving water turns a waterwheel.
Electrical energy becomes light
and heat energy when…
…we turn on a light bulb.
Electrical Energy
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Electrical energy,
called electricity, is
a form of energy.
Electricity is the
movement or flow
of electrons.
Electricity is a uniquely versatile form of
energy. It can be easily transformed into
other forms of energy.
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How is Electricity Produced?
Electricity is a natural phenomenon that is
produced in two very different ways:
Electromagnetism – The flow of
electrons is produced with
magnets moving near wires.
Photovoltaics - The flow of
electrons is produced when
sunlight shines on certain
substances.
Electricity from Electromagnetism
Most power plants make electricity with turbine
generators – simple machines that utilize the
natural phenomenon of electromagnetism:
When magnets
are moved near a
wire, electricity
will start to flow
through the wire.
Remember, electricity
is the flow of electrons.
What Turns the Turbine?
We use a variety of energy resources to make turbines spin
and produce electricity:
Flowing water
Blowing wind
Uranium
Coal
Natural Gas
Wood
These renewable natural resources
directly turn turbines in hydropower
plants and wind generators.
Nuclear reactors produce
steam which turns
turbines.
Combustible substances such as
these are burned to produce
steam which turns turbines.
Electricity from Photovoltaics
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Photovoltaic (PV) energy is
made from the light energy
of the sun.
Electricity is created when
sunlight shines on certain
substances causing the
electrons to move. Sunlight is
converted on an atomic level
directly into electricity! This
phenomenon only happens
with certain substances such
as silicon.
Understanding Electricity
Regardless of how it is produced,
electricity is the flow of electrons.
To better understand this flow of electrons
(electricity), we need to understand these
terms:
• Current
• Voltage
• Resistance
• Power
Powerful Basic Terms
Current –
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the rate of the flow of electrons
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measured in amperes or amps (A)
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analogous to the rate of water flow
through a hose
Powerful Basic Terms
Voltage –
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the force or pressure
causing electrons to
flow
measured in volts (V)
analogous to water
pressure
Powerful Basic Terms
Resistance –
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the degree to which the flow of
electrons is opposed or resisted
measured in Ohms (R)
analogous to the diameter of the
hose
Ohm’s Law
… is a scientific law that explains the
relationship between current, voltage,
and resistance:
A=V/R
(Amps = Volts / Resistance)
A
A
That is, the amount
of electric current is
equal to the voltage
(or pressure) divided
by the resistance on
that pressure.
Georg Simon Ohm
(1789-1854)
Ohm’s Law
… has many applications. We use it most
commonly it to calculate the amount of
electrical power:
W=VxA
(Watts = Volts x Amps)
What’s a watt?
Watts
A watt is a measure of electric power.
The more watts, the more work that is getting done.
…the brighter the light bulb
…the faster the motor turns, etc.
Electrical Power
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Power is the rate at which work gets
done, or the rate at which energy is
converted to different forms.
Electrical power is
measured in watts (W)
(or kilowatts, kW;
megawatts, MW; etc.)
100 watts
Electrical Energy
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Energy is a function
of power and time:
Wh = W x h
(how many watts for how many hours)
Electrical energy is measured in
watt-hours (Wh) (or kWh, MWh, etc.)
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Summary Concepts:
Energy can change forms
 Electricity is a major form
of energy (turbines & PV)
 Ohm’s Law power terms
(Watts = Volts X Amps)
 Electrical energy is
measured in watt-hours
 Watt-hours can be used to
compare different energy
sources
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