Objective The student knows that energy occurs in many forms and ...

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16 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Objective

The student knows that energy occurs in many forms and can be observed in cycles,
patterns, and systems. The student is expected to explore the uses of energy, including
mechanical, light, thermal, electrical, and sound energy.

Foundation

Energy

is power…the ability to do work. Every time anything moves, whether it’s the
wind, water, cars, trees, people, clocks, or animals, energy makes it happen. All
movement is energy. It takes energy to cook a meal, ride a bicycle, speak to a friend,
turn on a

computer, or listen to a song. We use energy every day. And just like a car
cannot run with an empty fuel tank, we need fuel to have the energy to complete tasks.
We gain our energy by consuming food. However, energy comes in different forms, all
of which

provide the power for an object to do work.

Mechanical energy is the energy which is possessed by an object due to its motion or
due to its position. Mechanical energy can be in the form of kinetic or potential energy.
Kinetic energy is the energy which c
omes from movement, and potential energy is the
stored energy which comes from an object’s placement. A ball flying through the air has
mechanical kinetic energy due to its mass and the speed of its movement. A tightly
wound spring in a wind up toy has pot
ential (stored) energy which will change to kinetic
energy (movement) when the spring is released. The string of a bow when drawn back
to shoot an arrow has mechanical (potential) energy, and, when released, changes to
kinetic energy to rapidly push the ar
row away from the bow.

A fire, a hot cup of coffee, or a heating stove has “thermal” or heat energy. Temperature
is really a measure of how much thermal energy an object has. The higher the
temperature the faster the particles, or molecules, of an object a
re moving. A cooking
stove heats the air inside the oven and when the cake mixture is placed in the oven, the
thermal heat of the air is transferred to the cake and it bakes. A microwave works
differently; it uses microwaves (Longer waves in length around
a food are the ones that
help heat food in the microwave itself.) to make the particles inside the food move more
rapidly. The resulting heat from the faster moving particles cooks the food.

Light energy is something we take for granted, but it is becoming

even more important
than ever. Light is able to travel through space, unlike sound that needs air or some
other medium to be transmitted. The portion of the electromagnetic spectrum that
humans can see is commonly called “light.” Light energy travels in a

straight line, but it
can be reflected. Light is reflected when it bounces off a shiny surface, such as a mirror.
Light can also be refracted, meaning it can be “bent” when it travels from one medium to
another. Because light travels slower in water than
in air, a pencil placed in a cup of
water will appear broken at the point of entry into the water. Curved lenses in
telescopes refract light in order to magnify the picture. Advances have been made even
recently to utilize light energy beyond just illumina
tion. Laser lights have become
important tools for doctors in surgery, for the manufacture of CD and DVD players and
computers, and even for teachers and speakers who use laser pointers in their
presentations.

All matter is made up of atoms. Electrical ene
rgy is created when electrons, small
particles of atoms, are caused to move along a path called a circuit. For the electrons to
flow and electricity to be evident, the circuit must be closed, that is to say the path along
which electrons are flowing must n
ot be broken, or open, anywhere along the way.
When we turn on a light, we are closing an electrical circuit and the lights come on.
When we flip the switch off, we open the circuit and the electricity ceases to flow.
Materials through which electrons flow

easily, such as copper wire, are called
conductors, while materials such as rubber or plastic, which do not allow electrons to
flow through them as easily, are called insulators. When electricity passes through coils
of wire, it can create an electromagne
tic field. All electric motors in everything from toy
cars to powerful fans use electromagnetic fields to create their power.

When we listen to someone speak, we are doing so because of the effects of sound
energy. Sound is created when an object vibrates.

The vibration of the object pushes
the air molecules nearby, which travel as sound waves to the listener. Our ears are
designed to be sensitive to these waves of sound, which our brain translates back into
the voice which we hear. Sound waves can be demon
strated by striking a metal rod and
feeling the vibration of the ringing rod or by simply placing our hand on our throat and
speaking. Sound energy requires a medium such as air or water to transmit, which is
why sound does not travel in space.

Energy can
be altered or changed within objects to meet the needs of people. We can
change the amount of sound energy in a radio or television to adjust the volume up or
down. We can adjust the amount of electrical energy in a light bulb if we want a room to
be brigh
ter or dimmer. A television is an example of how energy can be changed to
meet our needs. A television is powered by electrical energy, but the TV changes the
electrical energy into light energy so we see a picture and to sound energy so we hear
the voices
.

Without sources of energy, the Earth would be a lifeless planet. We have learned how
to harness the various forms of energy for our use, and in doing so, we have made our
lives more comfortable and enjoyable.