Transcript Energy Transformation and the Law of Conservation of Energy

Energy Transformation and the
Law of Conservation of Energy
Energy
• Energy is capacity to do work.
The international measurement system for energy is named "Système
International d'Unités" (french abbreviation: SI). The international
recognized unit for energy is the Joule (J), named after James Joule. He
was the scientist who for the first time demonstrated the rule that work
can be converted into heat.
• Work is a force applied to an object over a certain distance, such as pulling
or pushing a wooden block across your desk. Your muscles do work when
they facilitate body movement.
•
Any form of energy can be transformed into another form. This is called
energy transformation or energy conversion.
Energy doesn't disappear - just changes the forms.
Energy transformation is the process of changing energy from one form to
another. This process is happening all the time
The Main Energy Forms
• Electromagnetic energy (travels through
space)
• chemical energy
• mechanical energy
• nuclear energy
• electrical energy
• heat (thermal) energy
• energy of sound
Electromagnetic Energy
• The energy of electromagnetic waves, is also
known as radiant energy. The sun gives off
electromagnetic energy in the forms of waves.
The waves have both electrical and magnetic
properties.
Chemical Energy
Chemical energy is a potential energy. It comes
from the bonds of atoms and molecules.
Example: people utilize the chemical energy
from the food they consume, and their body
transforms it into mechanical energy, that
allows them to run, play games, do work and
etc.
Chemical Energy
Chemical energy is a potential energy. It comes
from the bonds of atoms and molecules.
Example: people utilize the chemical energy
from the food they consume, and their body
transforms it into mechanical energy, that
allows them to run, play games, do work and
etc.
Mechanical Energy
• Form of energy associated with the position
and motion of an object
– A quarter back football player transfers motion to
a football
– An object with mechanical energy can do work on
another object.
– The more mechanical energy the object has, the
more work it can do.
– Formula: ME=PE+KE
Nuclear Energy
• Nuclear Energy (atomic energy) is the energy
stored in the nucleus of an atom. That energy
can be released when we combine (energy
fusion) or split (energy fission) the nuclei.
Electrical Energy
• The energy of electric charges (electrons)
• Can be potential or kinetic
– An example of kinetic is lightening
– An example of potential is a battery
Thermal energy
• Thermal energy (heat energy) is the total
kinetic energy of atoms and molecules that
are constantly in motion. It’s the motion of
molecules.
Sound Energy
• Sound energy (energy of the sound) is a type of wave
motion. When we talk we breathe out that occurs the
effect of air motion which is because the air molecules
are vibrating. The vibrating molecules hit our
eardrums. That allow us to hear when we talk.
• Sound energy is possible to be converted into electrical
energy and to transmit from one place to another good example for it is the radio, phone.... After that
this electric energy could be transformed back to
sound energy that we can hear.
Energy Types
Energy type is different than energy form. All
energy forms could be set as two types of
energy - potential and kinetic energy
Kinetic energy is the motion.
Potential energy is the stored energy.
Energy Transformation
• Energy transformation is the process of changing
energy from one form to another. This process is
happening all the time.
• Any form of energy can be transformed into
another form. This process of energy
transformation is also known as energy
conversion.
Energy Transformation Examples
Energy Transformation is happening all of the time.
• Energy of food could be transformed in energy to
play.
• Chemical energy from coal, oil, natural gas can be
transformed into heat energy (process of burning
the fuel). The heat energy can be converted into
kinetic energy by gas turbines or into electrical
energy by generators; or it might be expelled into
the atmospere.
Energy Transformation Examples
(Cont’d)
• Sun gives the grass thermal energy. The grass
uses it to grow and transform it to a chemical
energy using the photosynthesis process.
• Rabbits eat grass and use it as an energy
source to grow and to have power to run.
• Hunting dogs like rabbits, but they can run
after them only if they have enough power to
do that. To have power dogs need to be feed.
Energy Transformation Examples
(cont’d)
If you turn on the power switch the electricity
bulb will use the electricity power and will
transform in to light.
The wind turbine uses the wind energy and
transforms in to electricity.
Solar panels transform light to electricity.
Where else can we find examples of
Energy Transformation?
• Look around you and try to find other
examples for energy transformation.
Energy Transformation and the Law of
Conservation of Energy
Work is an energy requiring process. So, how do you
describe energy? Energy is not a substance that can
be held, seen, or felt as a separate entity. We cannot
create new energy that is not already present in the
universe. We can only take different types materials
in which energy is stored, change their state, and
harness the energy that escapes from the system in
order to use it to do work for us. If the released
energy is not used, it will escape and be transformed
usually as heat.
Law of Conservation of Energy
• Energy doesn't disappear - it just can change forms.
• Energy is not destroyed or created – it can just change
forms or remain the same.
• The total amount of energy always stays the same. If
100% energy is put into any system or task, 100%
energy will come out either in it’s original form plus a
new form as multiple different energies, or it will come
out as 100% energy in a new form.
• The Law of Conservation of Energy states that the total
amount of energy in the universe is constant. This
means that all of the energy has to end up somewhere,
either in the original form or in a different form.
Law of Conservation of Energy (cont’d)
We can use this knowledge to determine the
amount of energy in a system, the amount lost as
waste heat, and the efficiency of the system.
Heat is the quantity of energy stored or transferred
by thermal vibrations of molecules. At absolute
zero (approx. -459 degrees Celsius), a system has
no heat energy. Heat is additive. If two masses
with heat energies of 5 joules and 10 joules are
added together, the added masses will have a
total heat energy of 15 joules. Heat and
temperature should not be confused.
Law of Conservation of Energy (cont’d)
We can use this knowledge to determine the
amount of energy in a system, the amount lost as
waste heat, and the efficiency of the system.
Heat is the quantity of energy stored or transferred
by thermal vibrations of molecules. At absolute
zero (approx. -459 degrees Celsius), a system has
no heat energy. Heat is additive. If two masses
with heat energies of 5 joules and 10 joules are
added together, the added masses will have a
total heat energy of 15 joules. Heat and
temperature should not be confused.
Law of Conservation of Energy (cont’d)
• The temperature of a system is the average vibrational energy of all
the molecules within the system. Temperature is not additive.
Putting two metal blocks that are 75o C together will leave the new
system at the same temperature; whereas if you’re talking about
heat, the total energy would be 150o C. Putting two masses that are
50o C and 100o C will make the new system somewhere between
50o C and 100o C. The temperature of which would be dependent
on the masses and heat capacities of each added element.
• When a fast-moving molecule collides with other molecules, it loses
some of its kinetic energy to those surrounding molecules. Those
molecules now have more energy than they had before. This extra
energy is manifested as vibrations within the molecule. Thus, the
temperature of the substance being hit will increase.
• For example, when ice cream melts, warmer molecules from the
surrounding air infuse the ice cream, collide with the colder
molecules, and the colder molecules speed up due to collissions
with the warmer molecules, and this causes the ice cream to melt.
Law of Conservation of Energy (Cont’d)
• We’re going to look at the transformation of energy
and the Law of Conservation of Energy by using an
example of an internal combustion engine.
• Combustion is where a chemical change takes place
when something is burned or oxidized. Combustion
produces heat and usually light. Internal means
inside—so internal combustion means a chemical
change is taking place due to burning, inside a
chamber.
• Internal combustion engines are machines that enable
other machines or parts of a machine to do work.
Internal combustion engines are found inside
automobiles, tractors, go-carts, or anything operated
by gasoline.
Law of Conservation of Energy (cont’d)
Law of Conservation of Energy (Cont’d)
• An example of how an internal combustion
engine works is in this video:
http://www.sciencekids.co.nz/videos/engineerin
g/carengine.html
Law of Conservation of Energy (cont’d)
• Internal combustion engines work this way: Into a chamber, a small
amount of fuel is drawn. The fuel is ignited (set on fire), by a spark
plug, and this causes a small explosion in the chamber. The
explosion (combustion), is what gives the engine power to move
parts attached to the chamber.
•
There are hundreds of parts used in engines to make it function
well enough to work for many years. When we look at an internal
combustion engine, it can give us a great insight both concepts of
transformation of energy and the law of conservation of energy
(also known as the first law of thermal dynamics). When an
internal combustion engine is running, it uses gasoline, a fuel, and
the fuel is combined with oxygen and a flame by the spark plug to
produce a very small explosion. This explosion produces power
which enables the engine to move cam shafts, axles, gears pulleys
and other parts of the vehicle.
Law of Conservation of Energy (cont’d)
• The next video shows the computer generated
assembly of an engine, and how all of the
parts work together.
• https://www.youtube.com/watch?v=l7MUL3v
tZ5o
How does an engine an example of
energy transformation and the law of
conservation of energy?
• Energy Transformation: No energy is ever lost, it it only
stays as it is, or it is transformed into different forms of
energy.
• In the case of an internal combustion engine: Potential
chemical energy (the fuel), is put into a chamber (container)
of the engine. The fuel is ignited (set on fire) in the
chamber, and when that happens, the potential chemical
energy changes to kinetic energy (during combustion); and
then the explosion of the chemical change causes engine
parts to move. The rest of the car parts move because the
engine powers the other car parts through a system of
pulleys, gears and levers. No energy is ever lost, it just
remains in its original form or is transformed.
Law of Conservation of Energy (cont’d)
• No energy is ever lost, it just remains form or is
transformed. In every energy transformation,
energy is conserved. This means that the form of
energy may change as it is used, but the amount of
energy is always 100%. 100% is input, and 100% is
output. According to the Law of Conservation of
energy, The total sum of potential and kinetic
energy stays the same. If 100% of one type of
energy is input, then 100 % must be output.
Law of Conservation of Energy
Energy Efficiency
• Energy efficiency can be thought of as the
efficiency with which we are capable of
utilizing a resource. If we don't use the energy
released from the chemical bonds in a
resource, the energy is transformed into heat,
sound, thermal vibrations, or light. The heat
energy is unusable, and is not lost, but
expelled through different parts of the engine
and the car’s parts including the tailpipe.
The Law of Conservatin of Energy
Energy Efficiency
• The more energy conversion steps there are in a
process, the more energy you lose as heat. For
example, in order to run a car, the chemical potential
energy in the gas (100% potential energy), converts
into thermal energy (or heat energy) by igniting the
fuel. The thermal energy is converted to mechanical
energy to make the engine run. This three step process
has an overall maximum efficiency of about 30%. That
means that 70% of the energy initially stored in the
gasoline was transformed to heat, and 30% was
actually converted into mechanical energy—the energy
that does the work.
The Law of Conservation of Energy
Energy Efficiency (cont’d)
• 100% potential chemical energy went into the
engine, and 70% left as heat energy and 30% left
as usable work output; so energy came in at
100% and energy left at 100%. The energy came
in as chemical potential energy, and left as
unusable heat and mechanical energy. No matter
what, the amount of energy that goes in is the
amount of energy that goes out. You’ll always
start at 100% energy and end up with 100%
energy, even when the energy has been
transformed into several different types of
energy.
Energy Conservation TOTD
An engine converts 95% of energy input into
useful work output. What happens to the
remaining 5% of the energy?
1.
2.
3.
4.
It is converted to heat or
to some other form of
unusable energy.
It is destroyed in the
process of converting
from one type of energy
to another.
It is stored in the engine
for later use.
It is lost along with the
mass of the fuel.