ENERGY
Energy is the ability to do work and there are many types of energy.
Types of Energy
Energy has a number of different forms, all of which measure the
ability of an object or system to do work on another object or system.
Kinetic Energy
Consider a baseball
flying through the air. The ball is said to have “kinetic energy” by
virtue of the fact that its in motion relative to the ground. You can see that it is has energy because it can do “work” on an object on the ground if it collides with it (either by pushing on it and/or damaging it during the collision).
Potential Energy
Consider a book sitting
on a table. The book is said to have “potential energy” because if it
is nudged off, gravity will accelerate the book, giving the book kinetic
energy. Because the Earth’s gravity is necessary to create
this kinetic energy, and because this gravity depends on the Earth being
present, we say that the “Earth-book system” is what really possesses
this potential energy, and that this energy is converted into kinetic energy as the book falls.
Heat Energy
where motion or rise in temperature is caused by heat like a fire in your fireplace.Consider
a hot cup of coffee. The coffee is said to possess “thermal energy”, or
“heat energy” which is really the collective, microscopic, kinetic and
potential energy of the molecules in the coffee (the molecules have
kinetic energy because they are moving and vibrating, and they have
potential energy due their mutual attraction for one another – much the
same way that the book and the Earth have potential energy because they
attract each other). Temperature is really a measure of how
much thermal energy something has. The higher the temperature, the
faster the molecules are moving around and/or vibrating, i.e. the more
kinetic and potential energy the molecules have.
Mechanical Energy
is the energy of motion that does the work like the wind turns a windmill.
Electrical Energy
is when motion, light or heat is produced by an electrical current like the electric coils on your stove.All
matter is made up of atoms, and atoms are made up of smaller particles,
called protons (which have positive charge), neutrons (which have
neutral charge), and electrons (which are negatively charged). Electrons
orbit around the center, or nucleus, of atoms, just like the moon
orbits the earth. The nucleus is made up of neutrons and protons.Some
material, particularly metals, have certain electrons that are only
loosely attached to their atoms. They can easily be made to move from
one atom to another if an electric field is applied to them. When those
electrons move among the atoms of matter, a current of electricity is created.
This is what happens in a piece of wire when an electric field, or voltage,
is applied. The electrons pass from atom to atom, pushed by the
electric field and by each other (they repel each other because like
charges repel), thus creating the electrical current. The measure of how
well something conducts electricity is called its conductivity, and the reciprocal of conductivity is called the resistance.
Copper is used for many wires because it has a lower resistance than
many other metals and is easy to use and obtain. Most of the wires in
your house are made of copper. Some older homes still use aluminum
wiring.The energy is really transferred by the chain of
repulsive interactions between the electrons down the wire – not by the
transfer of electrons per se. This is just like the way that water
molecules can push on each other and transmit pressure (or force)
through a pipe carrying water. At points where a strong resistance is
encountered, its harder for the electrons to flow – this creates a “back
pressure” in a sense back to the source. This back pressure is what
really transmits the energy from whatever is pushing the electrons
through the wire. Of course, this applied “pressure” is the “voltage”.
As the electrons move through a “resistor” in the circuit, they interact
with the atoms in the resistor very strongly, causing the resistor to
heat up – hence delivering energy in the form of heat. Or, if the
electrons are moving instead through the wound coils of a motor, they
instead create a magnetic field, which interacts with other magnets in
the motor, and hence turns the motor. In this case the “back pressure”
on the electrons, which is necessary for there to be a transfer of
energy from the applied voltage to the motor’s shaft, is created by the
magnetic fields of the other magnets (back) acting on the electrons – a
perfect push-pull arrangement
Chemical Energy
is the chemical reaction causing changes; food and fuel both store chemical energy.Consider
the ability of your body to do work. The glucose (blood sugar) in your
body is said to have “chemical energy” because the glucose releases
energy when chemically reacted (combusted) with oxygen. Your muscles use this energy to generate mechanical force and also heat. Chemical energy is really a form of microscopic potential energy,
which exists because of the electric and magnetic forces of attraction
exerted between the different parts of each molecule – the same
attractive forces involved in thermal vibrations. These parts get
rearranged in chemical reactions, releasing or adding to this potential
energy.
Gravitational Energy
where motion, like water going over a dam, is caused by gravity’s pull.
Electrochemical Energy
Consider
the energy stored in a battery. Like the example above involving blood
sugar, the battery also stores energy in a chemical way. But electricity
is also involved, so we say that the battery stores energy
“electro-chemically”.
Electromagnetic Energy (light)
Consider the
energy transmitted to the Earth from the Sun by light (or by any source
of light). Light, which is also called “electro-magnetic radiation”. Why
the fancy term? Because light really can be thought of as oscillating,
coupled electric and magnetic fields that travel freely through space
(without there having to be charged particles of some kind around).
It turns out that light may also be thought of as little packets of energy called photons (that is, as particles, instead of waves). The word “photon” derives from the word “photo”, which means “light”.
Photons are created when electrons jump to lower energy levels in
atoms, and absorbed when electrons jump to higher levels. Photons are
also created when a charged particle, such as an electron or proton, is
accelerated, as for example happens in a radio transmitter antenna.
But because light can also be described as waves, in addition to being a
packet of energy, each photon also has a specific frequency and
wavelength associated with it, which depends on how much energy the
photon has (because of this weird duality – waves and particles at the
same time – people sometimes call particles like photons “wavicles”).
The lower the energy, the longer the wavelength and lower the
frequency, and vice versa. The reason that sunlight can hurt your skin
or your eyes is because it contains “ultraviolet light”, which consists
of high energy photons. These photons have short wavelength and high
frequency, and pack enough energy in each photon to cause physical
damage to your skin if they get past the outer layer of skin or the lens
in your eye. Radio waves, and the radiant
heat you feel at a distance from a campfire, for example, are also forms
of electro-magnetic radiation, or light, except that they consist of
low energy photons (long wavelength and high frequencies – in the
infrared band and lower) that your eyes can’t perceive. This was a great
discovery of the nineteenth century – that radio waves, x-rays, and
gamma-rays, are just forms of light, and that light is electro-magnetic
waves
Sound Energy
Sound
waves are compression waves associated with the potential and kinetic
energy of air molecules. When an object moves quickly, for example the
head of drum, it compresses the air nearby, giving that air potential
energy. That air then expands, transforming the potential energy into
kinetic energy (moving air). The moving air then pushes on and
compresses other air, and so on down the chain. A nice way to think of
sound waves is as “shimmering air”.
Nuclear Energy
The Sun, nuclear reactors, and the interior of the Earth, all have
“nuclear reactions” as the source of their energy, that is, reactions
that involve changes in the structure of the nuclei of atoms. In the Sun, hydrogen nuclei fuse (combine) together to make helium nuclei, in a process called fusion,
which releases energy. In a nuclear reactor, or in the interior of the
Earth, Uranium nuclei (and certain other heavy elements in the Earth’s
interior) split apart, in a process called fission. If
this didn’t happen, the Earth’s interior would have long gone cold! The
energy released by fission and fusion is not just a product of the
potential energy released by rearranging the nuclei. In fact, in both cases, fusion or fission, some of the matter making up the nuclei is actually converted into energy. How can this be? The answer is that matter itself is a form of energy! This concept involves one of the most famous formula’s in physics, the formula,
E=mc2.
Link : http://www.way2science.com/energy/
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