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Key words: light, heat, sound, kinetic, potential (stored), nuclear,
chemical (stored), electrical, Joules, conduction, convection, radiation, fossil fuels,
alternative energy, solar, wind, tidal, thermal, quantum, NIMBY, electromagnetic,
electrostatic, E = MC2
INDEX
Forms of energy:
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Light:
this is a part of the electromagnetic
spectrum. |
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Heat: this is the energy of vibrating particles in a substance. |
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Sound:
this is the energy of vibrating particles. |
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Chemical: this is the energy held in the molecules of any substance. |
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Kinetic: this is the energy of a moving object. |
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Potential: this is the energy due to the
pull of gravity on an object. |
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Nuclear: this is the energy present in
atoms and released in nuclear reactions. |
Sources of energy:
Different Forms of Energy:
Light is a form of energy. Visible light is just a small section of the electromagnetic spectrum. "Richard Of
York Gave Battle In Vain" is a mnemonic, i.e. an aid to memorising the colours of the
spectrum. Red, Orange, Yellow, Green, Blue, Indigo, Violet. The red end of the spectrum
has longer wavelength and lower energy, the violet end of the spectrum has shorter
wavelength and higher energy.
Infra Red is also a form of light energy, but the wavelength is
too long for the human eye to detect it. Infra Red can be detected by speccial
photographic films and by some animals such as the pit viper. Infra Red waves have a
longer wavelength than visible light and they have less energy. However, Infra Red light
is absorbed by your skin and makes you feel warm.
Electromagnetic waves longer than Infra red are micro-waves (in
your micro-wave oven) and radio waves. Radio waves can be anything from a fraction of a
millimetre to kilometres long. There is some more information about radio waves in my Amateur Radio Web.
Ultra Violet light is also a part of the electromagnetic
spectrum. Here the waves are much shorter than visible light and there is more energy. It
is the Ultra Violet UV light which gives us our sun tans or skin cancers. UV can be used
to kill micro-organisms on our food. It can also be used to detect markings on personal
property. You can mark you personal property with your name and address with an ink which
does not reflect visible light but does reflect UV. The police will be able to see your
name and address on your property when they shine UV light onto it. The thief did not see
your markings when he took your property! Of course if he had a UV light he would have
seen the markings and not stolen your property.
Electromagnetic waves shorter than UV light include X-rays and
gamma rays. They have so much energy they can even get through sheets of metal. This is
very useful if you want to look for cracks in aeroplane wings.
When light energy (visible or invisible) falls onto an object, it
can do one of three things. It may be reflected, it may be absorbed, or it may pass
straight through. When light is absorbed by an object the light energy is turned into heat
energy or chemical energy. If you shine white light (a mixture of all the colours of the
spectrum) onto a leaf, some of the light passes through, some of the light is reflected,
and some of the energy is absorbed. When leaves absorb light the energy is turned into
heat and chemical energy. Photosynthesis is the process by which green plants turn light
energy into chemical energy.
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Heat is another form of energy. At absolute zero -273°C the particles do not
vibrate. The particles are COLD. I think that it is like this in outer space, but I have
never been there to find out.
When we heat something we make the particles move faster. You may
think that ice is very cold; what you really mean is thai ice is colder than your body.
Actually it is quite hot compared to outer space and the molecules in the ice are
vibrating quite fast. When the molecules vibrate too fast, the ice melts. When the
molcules in water vibrate much too fast the water boils. If you think that boiling water
is very hot, take a holiday on the sun; the surface of the sun is millions of degrees!
The amount of heat energy in an object is measured in Joules.
There are some very easy calculations: if you heat 1 gram of water by 1 degree celsius you
will use 4.2 Joules. So you could work out how many Joules of heat energy are used to heat
the water for your bath. Send me e-mail to
check your calculation.
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Sound energy is the energy of vibrating particles. This is very simple. When
you pluck a guitar string you are giving it kinetic energy. The vibrating string makes the
air around it vibrate. You can hear these vibrations (the sound of the guitar) because the
vibrating air or sound waves travel to your ear and make your eardrum vibrate.
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Chemical energy is the energy held in the molecules of any substance. In any
chemical reaction it is very unlikely that there is the same amount of energy in the
initial reactants and the products of the reaction. If there is more energy in the
reactants than in the products the extra energy is usually released as heat. We call this
kind of reaction an exothermic reaction because it gives out heat. We could also call it
an exergonic reaction because it gives out energy.
The energy released in an exergonic reaction could be
released as heat, light, electrical energy, or even as sound energy. If you sit near to a
fire in the winter, you can enjoy the heat as well as seeing the flames and hearing the
crackle as the wood or coal burns.
The chemical energy in our food is released in the
process of tissue respiration. This energy can be used for other activities like moving
and growing.
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Kinetic energy is the energy of a moving object. It is easy to calculate how
much kinetic energy a moving object has. The equation is E = ½MV2 ; but remember to get the units right. Next time you see me
coming down the road on my motorcycle check my velocity; this should be in metres per
second. I will probably be doing 100 miles per hour; you will have to do a conversion. The
motorcyle is about 220 Kilograms. I am 69 Kgm (I lost a little weight this holidays). How
much kinetic energy do I have? E-mail
your answer. Your answer should be in Joules or
even Kilojoules.
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Potential energy is the energy of an object due to the force of gravity. It is
easy to calculate how much potential energy an object has. The equation is E = FH; again you must remember
to get the units right. The height of the object is measured in Metres and the force of
gravity on the object is measured in Newtons. I am still only 69 Kgm so on this planet
(Earth) the force on me will be 690 Newtons. How much energy do I use going upstairs if
the stairs are 3.5m high? E-mail
your answer.
I read about a man who jumped out of an aeroplane at
20,000 ft without a parachute (you will have to convert the feet into metres). He had a
good reason to jump out; the aeroplane was on fire, but I forget why he didn't have a
parachute. Perhaps he forgot it. Anyway, all his potential energy got turned into kinetic
energy. I am sure that he was very surprised to find himself alive when he landed: he just
got up and walked away. He landed in a forest covered in deep snow, and this saved him.
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Nuclear energy is the energy present in atoms and released in nuclear
reactions. Nuclear reactions take place in stars including the sun. These reactions also
take place in substances like Uranium and Plutonium. There are two main kinds of nuclear
reactions, fission and fusion. In the sun and other stars, atoms of Hydrogen combine to
form Helium, this is called fusion. Fusion only takes place at very high temperatures and
pressures. When two atoms of Hydrogen combine to form one atom of Helium, some of their
mass is converted into energy. This is nuclear energy.
The nuclear reactions in the sun generate an enormous
amount of energy. Some of this energy is converted into light energy and radiated out in
all directions. Without this energy we would be in serious trouble. No light means no
photosynthesis means no food. No light would also mean no heat!!!
Fission reactions also release energy. When Uranium or
Plutonium atoms split in half, some of the mass is converted into energy. It is possible
to make these reactions happen on Earth. Unfortunately some of the products of fission are
very unpleasant. We all seem to argue about nuclear waste. The solution to the problem of
nuclear waste is very simple and most people agree about it: the solution is NIMBY.
So everything is alright, we can use fission reactions to get energy as long as we use NIMBY.
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Converting one kind of energy into another:
The chemical energy in glucose (the sugar in my blood)
can be converted into kinetic energy and heat energy in the process of tissue respiration.
The same kind of thing happens in the petrol engine in your car. The only difference is
that you cannot hear me when I move but you can hear the car engine; some of the chemical
energy in the petrol engine is converted into sound, some into heat and some into movement
or kinetic energy.
Electrical energy can be converted into kinetic energy
and heat energy by an electric motor.
Electrical energy can be converted into light energy,
sound energy and heat energy in a television set.
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Energy Sources:
Don't get confused between kinds of energy and sources of energy.
Read the exam question carefully. Are you being asked to name the different kinds of
energy or are you being asked to say where we get our energy from?
Fossil Fuels: It took
millions of years to make fossil fuels. These are coal, oil, natural gas, and peat. We can
burn them to get energy but one day these sources of fuel will run out. Burning fossil
fuels also causes pollution and perhaps Global Warming.
Alternative Energy: It
is possible to obtain energy from "clean" sources. Solar energy (light from the
Sun) can be used to generate electricity. Apart from making the solar panels and other
equipment to distribute the electrical energy, solar power does NOT casuse pollution. It
will NOT run out for millions of years.
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This page is still "under
construction", please be patient.
Glossary:
Light is an electromagnetic disturbance. We can
think of light as being made of tiny particles called photons, or we can think of it as
being made of waves. Both models help us to understand how light behaves. Here are some
simple rules:
- Light always travels at the speed of light which is about 300,000,000
metres per second. We use the symbol "C" to represent this
figure.
- Light always travels in straight lines, (at least it does on my
planet) unless it is reflected or refracted by passing from one material into another.
- Light is reflected when it falls onto a shiny surface.
- Light is refracted when it passes from one material into another,
i.e. out of the air and into water or in and out of glass. Light can also be refracted by
passing through hot and cold air; this is what causes a mirage.
Heat is caused by vibrations of the atoms and
molecules of substances. The hotter the substance is, the faster the particles vibrate. At
absolute zero ( -273degrees C) the particles stop moving, they have NO heat energy.
Sound energy is the energy of vibrating
particles in the air or even water. The sound travels in waves radiating out from the
source of the sound.
Nuclear
Chemical
Electrical
Solar Power is light energy from the Sun.
Wind Power is used to generate electrical
energy.
Tidal Energy is available if we can make
machines to harness the power of the waves on the sea or the tides as they come in and go
out.
Thermal Energy is a renewable source of energy.
The inside of the earth is very hot. It is possible to use this energy by
Quantum: this is the smallest possible amount of
energy that can exist by itself. It is NOT possible to have less than one quantum of
energy.
Electromagnetic
Electrostatic
E = MC2 I
have been told that this is the only important discovery in physics since Isaac Newton
worked out how gravity made planets go round the sun etc.. What this famous equation says
is that if we totally destroyed an obect by turning all its mass (M) into
energy then the amount of energy produced (E) would be equal to the mass
multiplied by the square of the speed of light (C2).
NIMBY stands for Not
In My Back Yard. i.e.
bury the nuclear waste some where else.
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