Potential Energy is any type of stored energy. It
can be chemical, nuclear,
gravitational, or mechanical .
Kinetic Energy is found in movement. An airplane
flying or a meteor plummeting each have kinetic energy. Even the tiniest things
have
kinetic energy, like atoms vibrating when they
are hot or when they transmit sound waves . Electricity is the kinetic
energy of flowing electrons between atoms.
Energy can shift between forms, but it is never destroyed or created .
A car transforms the potential energy trapped in
gasoline into various types of
energy that help the wheels turn and get the car
to move. Most of the energy is
converted to thermal energy, which is an
unorganized form of energy that is
difficult to convert into a useful form.
Power plants transform one form of energy into a
very useful form, electricity.
Coal and natural gas plants use the chemical
potential energy trapped in fossil
fuels. Nuclear power plants change the nuclear
potential energy of uranium or
plutonium into electricity too. Wind turbines
change the kinetic energy of air
molecules in wind into electricity. Hydroelectric
power plants take advantage of
the gravitational potential energy of water as it
falls from the top of a dam to the
bottom.
These transformations are hardly perfect. An
efficient fossil fuel power plant
loses more than half of the energy it creates to
forms other than electricity, such
as heat, light, and sound.
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FORMS OF POTENTIAL ENERGY
GRAVITATIONAL ENERGY
Systems can increase gravitational energy as mass moves away from
the
center of Earth or other objects that are large
enough to generate significant
gravity (our sun, the planets and stars).
For example, the farther you lift an anvil away
from the ground, the more
potential energy it has. Lifting the anvil is
called work, which is an interaction in
which energy is transferred from one system (the
person) to another (the anvil).
The person has to do more work in order to carry
the anvil higher, and the
higher the anvil is carried, the more
gravitational potential energy is stored in the
anvil. If the anvil is dropped, that potential
energy transforms to kinetic energy
as the anvil moves faster and faster toward
Earth.
CHEMICAL
Chemical energy is stored in the bonds between
the atoms in compounds. This
stored energy is transformed when bonds are
broken or formed through
chemical reactions. Like letters of the alphabet
that can be rearranged to form new words with very different meanings, atoms
move around
during chemical reactions, and they form new
compounds with vastly different personalities.
When we burn sugar (a compound made of the
elements hydrogen, oxygen, and
carbon) in our bodies, the elements are reorganized into
water and carbon dioxide. These reactions both
absorb and release energy, but the overall result is that we get energy from
the sugar, and
our bodies use that energy to do work.
Chemical reactions that produce net energy
are exothermic. When wood is burned, the
chemical reactions taking place are
exothermic.
Electromagnetic and thermal energy are released. Only some
chemical reactions release energy.
Endothermic reactions need energy to
start and to continue, such as by adding heat or
light.
NUCLEAR
Today’s nuclear power plants are fueled by fission . Uranium or plutonium atoms are
broken apart, freeing lots of energy. Hydrogen atoms in
the sun experience nuclear fusion , combining to
form helium and subsequently releasing large amounts of energy in the form of
electromagnetic radiation and thermal energy.
Nuclear energy is the stored potential of the
nucleus of an atom. Most atoms are
stable on Earth; they keep their identities as particular
elements, like hydrogen, helium,
iron, and carbon, as identified
in the Periodic Table of Elements. The number of protons in the nucleus tells
you which element it is. Nuclear reactions change the fundamental identity of elements by
splitting up an atom’s nucleus or fusing together
more than one nucleus. These changes are
called fission and
fusion, respectively.
ELASTIC
Elastic energy can be stored mechanically in a
compressed gas or liquid, a coiled spring, or a stretched elastic band. On an
atomic scale, the
stored energy is a temporary strain placed on the
bonds between atoms, meaning there’s no permanent change to the material. These
bonds absorb energy as they are stressed, and
release that energy as they relax.
·
FORMS OF KINETIC ENERGY
MOTION
A moving object has kinetic energy. A basketball
passed between players shows
translational energy. That kinetic energy is proportional to
the ball’s mass and the square of its velocity.
To throw the same ball twice as fast, a player does more work and transfers
four times the
energy.
If a player shoots a basketball with backspin or
topspin, the basketball will also have
rotational energy as it spins. Rotational energy is proportional to how
many times it spins per second, as well as the ball’s mass, and the size and
shape of the ball.
In shooting a basketball, players often try to
add rotational energy as backspin, because it results in the greatest slowdown
in speed when
the basketball hits the rim or the backboard,
increasing the chance that the ball stays near the basket. The opposite
direction of spin, a
topspin, can be used in games like tennis,
because it will help speed up a ball after impact and lowers the angle it
travels after the bounce.
THERMAL ENERGY AND TEMPERATURE
Thermal energy is directly related to
temperature. We can’t see individual
atoms vibrating, but we can feel their kinetic energies as
temperature. When there’s a difference between
the temperature of the environment and a system within it, thermal energy is
transferred
between them as heat.
A hot cup of tea loses some of its thermal energy
as heat flows from the tea to the air in the room. Over
time, the tea cools to the same temperature as
the room air. At the same time, the thermal energy in the
room air increases due to heat transfer from the
tea. However, the thermal capacitance of the room air is
much larger than the tea, so the temperature of
the air in the room increases by very little – so little that a
person in the room wouldn’t notice it.
Heat flows
spontaneously from high temperature objects to nearby low temperature objects,
until all
objects reach the same temperature, called
thermal equilibrium. Some materials are easier to heat up or
cool down than others. The thermal capacitance,
or heat capacity, of a material tells us how much energy it
takes to raise that material one degree in temperature.
A pound of water has greater thermal capacitance
than the same amount of stainless steel, for
example. In moments, an empty one pound pot on the stove heats to 212 degrees
Fahrenheit
(the boiling temperature of water). If you pour a
pound of water into the pot, it will take much longer than the empty pot to
reach the same
temperature, because water needs more energy to
get as hot as steel.
SOUND
Sound waves are made when stuff vibrates – like
strings on an instrument or gas molecules in the air. Sound waves travel when
the vibrating
stuff causes stuff surrounding it to also
vibrate. This happens in liquid, solid, or gaseous states. Sound cannot travel
in a vacuum because a
vacuum has no atoms to transmit the vibration.
Solids, liquids, and gases transmit sounds as
waves, but the atoms that pass along the sound don’t travel the way photons do.
The sound
wave travels between atoms, like people passing
along a “wave” in a sports stadium. Sounds have different frequencies and wavelengths
(related to pitch) and different magnitudes
(related to how loud).
Even though radio waves can transmit information
about sound, they are a completely different kind of energy, called electromagnetic
energy.
ELECTROMAGNETIC RADIATION
Electromagnetic energy is the same as radiation
or light. This type of energy can take the form of visible light,
like the light from a candle or a light bulb, or
invisible waves, like radio waves, microwaves, x-rays and
gamma rays. Radiation — whether it’s coming from
a candle or an x-ray tube — can travel in a vacuum.
Sometimes physicists describe electromagnetic
radiation as being composed of particles – tiny packets of
energy called
photons. Each photon has a characteristic frequency, wavelength, and
energy, but all photons
travel at the same speed, the speed of light, or
nearly 1 billion feet per second.
Electromagnetic energy can be converted to
the chemical energy stored in plants
through photosynthesis,
the process by which plants and algae use the
sun’s radiation to turn carbon dioxide gas into sugar and
carbohydrates.
ELECTRIC
Electric energy is to the kinetic energy of
moving electrons, the negatively-charged particles in atoms
REFERENCE:BURNANENERGYJOURNAL.COM
