What
is Energy?
Energy does things for us. It moves cars along the road
and boats in the water. It
bakes a cake in the oven and keeps ice frozen in the
freezer. It plays our favorite songs
and lights our homes at nights so we can read a good
book.
Energy helps our bodies grow and our minds think. Energy
is a doing, moving,
working thing.
Energy is defined as the ability to do work, and that
work can be divided into five
main tasks:
1. Energy gives us light.
2. Energy gives us heat.
3. Energy makes things move.
4. Energy makes things grow.
5. Energy makes technology work.
Forms of Energy
You probably already have a good idea that energy takes
different forms. Energycan light our homes or heat them.
There are six forms of energy:
Mechanical
Mechanical energy puts something in motion. It moves cars
and lifts elevators. It pulls, pushes, twists, turns, and
throws. A machine uses mechanical energy to do work and
so do our bodies! We can throw a ball or move a pencil
across paper.
Kinetic energy is a kind of mechanical energy. It is the
energy of a moving object. A moving car has kinetic
energy. A stalled car does not, however, if it's poised
at the top of a hill, it may have potential energy.
Potential energy is the energy an object has because of
its position. Potential energy is resting or waiting
energy. A spring is a good example of potential energy.
Energy can be stored in the spring by stretching or
compressing it. The sum of an object's kinetic and
potential energy is the object's mechanical energy.
Chemical
Chemical energy is the energy stored in food, wood, coal,
petroleum, and other fuels. During photosynthesis,
sunlight gives plants the energy they need to build
complex chemical compounds. When these compounds are
broken, the stored chemical energy is released in the
form of heat or light. What happens to a wood log in a
fireplace? Burning the wood breaks up the compounds,
releasing the stored chemical energy in the form of
thermal and radiant energy.
Electrical
Electrical energy is a kind of kinetic energy. It is the
energy of moving electrons. Everything in the world is
made up of tiny particles called atoms. Atoms are made up
of even tinier particles called electrons, protons, and
neutrons. Electricity is produced when something upsets
the balancing force between electrons and protons in
atoms. We can use electricity to perform work like
lighting a bulb, heating a cooking element on a stove,
moving a motor.
Radiant
Radiant energy is commonly called light energy. But light
energy is only one kind of radiant energy. All waves emit
energy. Radio and television waves are other types of
radiant energy. So are gamma rays and x-rays. Light waves
do work by wiggling the receptors in the back of our
eyes.
Thermal
Thermal energy, or heat energy, is also a special kind of
kinetic energy. It is the energy of moving or vibrating
molecules. The faster the molecules move, the hotter an
object becomes and the more thermal energy it possesses.
Thermal energy can do work for us or it can be the result
of doing work. Do this: Rub you hands together quickly.
What do you feel? You should feel heat. When two objects
slide against each other they produce friction which
transforms into heat.
Nuclear
Nuclear energy is energy locked in the nucleas of the
atom. It is the force that binds the nucleus of the atom
together. The energy can be released when atoms are
combined or split apart. Nuclear power plants split atoms
in a process called fission. The sun combines atoms in a
process call fussion. In both fission and fusion, mass is
converted into energy, according to Einstein's Theory, E
= mc2.
Most power plants are about 35% efficient. That means
that for every 100 units of energy that go in a plant, 65
units are "lost" as one form of energy is
converted to another form. Thirty-five units are left to
do usable work.
|
All of the cars that we use
are driven by mechanical energy. See across for the
definition of mechanical energy.
Here power lines are transmitting electical energy. This
type of energy is used to perform work around the house
such as light a light bulb. |
