Key Words: light, heat, sound, kinetic energy, potential energy, nuclear, chemical, electrical, Joules, conduction, convection, radiation, fossil fuels, alternative energy, solar, wind, tidal, thermal,electromagnetic,electrostatic, E=MC², NIMBY.
- Light: this is a part of the electromagnetic spectrum.
- Heat: this is the energy of vibrating particles in a substance.
- Sound: this is also the energy of vibrating particles.
- Chemical: this is the energy held in the bonds between atoms in a molecule.
- Kinetic: this is the energy of a moving object.
- Potential: this is the energy due to the pull of gravity.
- Nuclear: this is the energy present in atoms and released in nuclear reactions.
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. 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!
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.
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.
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.
Kinetic energyis 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.
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.
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
Converting one form 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.
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.
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.
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.
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).