Tucson Solar Schools Project

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Tucson Solar Schools Project

• Introduction to Energy
• and
• Electricity

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About Energy

• In everyday language, we use the word energy in
  many ways.
• In science, energy is defined as the capacity to
  do work.

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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!
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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.)
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Forms of Energy

• Energy occurs in many forms
• Light
• Heat
• Sound
• Chemical
• Gravitational (energy of position)
• Nuclear
• Kinetic (motion or mechanical energy)
• Electrical energy (electricity)

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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.
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Electrical Energy

• 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.
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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.
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What Turns the Turbine?
We use a variety of energy resources to make
turbines spin and produce electricity
These renewable natural resources directly turn
turbines in hydropower plants and wind generators.
Flowing water Blowing wind
Nuclear reactors produce steam which turns
turbines.
Uranium
Combustible substances such as these are burned
to produce steam which turns turbines.
Coal Natural Gas Wood
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Electricity from Photovoltaics

• 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.

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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

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Powerful Basic Terms

• Current
• the rate of the flow of electrons
• measured in amperes or amps (A)
• analogous to the rate of water flow through a hose

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Powerful Basic Terms

• Voltage
• the force or pressure causing
  electrons to flow
• measured in volts (V)
• analogous to water pressure

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Powerful Basic Terms

• Resistance
• the degree to which the flow of electrons is
  opposed or resisted
• measured in Ohms (R)
• analogous to the diameter of the hose

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Ohms Law
is a scientific law that explains the
relationship between current, voltage, and
resistance A V / R (Amps Volts / Resistance)
That is, the amount of electric current is equal
to the voltage (or pressure) divided by the
resistance on that pressure.
A
A
Georg Simon Ohm (1789-1854)
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Ohms Law
has many applications. We use it most commonly
it to calculate the amount of electrical power
W V x A (Watts Volts x Amps) Whats a watt?
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Watts

• A watt is a measure of electric power.

The more watts, the more work that is getting
done.
the faster the motor turns, etc.
the brighter the light bulb
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Electrical Power

• 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
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Electrical Energy

• 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)
• Ohms Law power terms (Watts Volts X Amps)
• Electrical energy is measured in watt-hours
• Watt-hours can be used to compare different
  energy sources