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What is energy?

Energy is the ability to do work. It's what you get when you burn fuel

'Burn' in this sense doesn't have to mean burning with flames, like in a car engine or a fire. It can also mean what happens inside your body when your muscles use energy to make you move about. That too is a sort of slow burning of fuel (sugars)and it releases heat. That's why you get hot when you run about a lot
(= stored energy) to move something like a car or kick a ball (= do work). That fuel can be stuff like coal or gas or the hydrogen
Hydrogen is a gas. Almost all the sun is made of it and it 'burns' in a very special way called nuclear fusion. This is not 'burning' the way we usually think of it, like a bonfire. Nuclear fusion can make enormous amounts of heat and light energy from very tiny amounts of hydrogen fuel. It is this same reaction which powers hydrogen bombs.
which powers the sun. What you get is heat and light energy. You can feel the heat from a fire or from the sun on your skin. And sunlight makes our daytime.

Your body, for example, can change the stored POTENTIAL energy in the food you've eaten into 'work' energy, called KINETIC energy. Kinetic energy powers your muscles to make you run or jump.
Energy can be changed from one form to another but it
This is called the First Law of Thermodynamics
can't be created or destroyed

electric socketsPeople have learned to use stored energy to do useful work for them. By burning coal, you can use the chemical energy

Chemical Energy
Energy can be stored in chemical form such as oil, coal, sugar, fat or in batteries. This stored energy is POTENTIAL energy. To get it to do work, you have to burn the oil or coal. You use stored sugar and fat from the food you eat to 'burn' and use as KINETIC energy for moving about.
stored in the coal to heat up water until it becomes steam which then drives large machines
Electricity generators
These machines are called turbo-generators. They are really two machines: one is a turbine, driven at high speed by the powerful, high pressure steam; the spinning turbine drives the generator which 'does work' and makes the electricity, the new and useful form of energy which everyone uses.
to generate electricity. Electricity is another form of energy and it too can be made to do useful work, like running your washing machine or powering your computer and mp3 player. But electricity doesn't have to be made by burning coal. It can be made from renewable
Renewable energy
You've probably heard about renewable energy, often also called 'alternative energy', meaning it's an alternative to polluting fuels like coal and oil. Renewable energy comes directly (as heat and light) or indirectly (as wind and waves) from the sun. I'll tell you more about it later in this guide.
energy sources like wind and water power. It can also be made by nuclear power,
Nuclear power
Nuclear power uses the enormous amount of heat produced by splitting atoms of uranium, a very heavy metal which is found in some of the Earth's rocks. Apart from the heat inside the Earth (which makes volcanoes erupt), it is the only source of energy which has nothing to do with the sun. I'll tell you more about this later on in this guide.

Types of Energy

Potential energy is stored in some sort of solid body and has the potential to do work. There are four types:

Chemical: energy stored in things like the food you eat, fossil fuels and explosives
Elastic: energy stored in a stretched elastic band or spring, for example
Gravitational: the energy a body has because it's near to another large body, like a planet. If a big hole opened up under you, you'd be pulled (fall) down it because of the pull (= energy) of Earth's gravity
Nuclear: energy stored in the nucleus of atoms. This energy is used in nuclear power stations to generate heat and is called nuclear fission (= splitting apart). The Sun and all the other stars shine because of the energy released when atoms of hydrogen fuse together. This is called nuclear fusion.

There are many different types of energy but they're really all variations of one (or some) of these:
Heat: if you touch something hot, it can be very painful as that heat flows into you
Kinetic: this is the energy which a moving body has. If someone kicks a ball hard and it hits you, it hurts because your body has had to suddenly absorb all that energy and stop the ball
Electrical: this is the kinetic energy of moving charges in an electrical circuit. One example is electricity flowing through an old-fashioned light bulb. It makes both heat and light by passing through a resistance (the light bulb's filament)
Electromagnetic: light and other radiation are all forms of electromagnetic energy

I used a lot of energy writing this! Now what sort of energy

What sort of energy?
Well it's not nuclear, is it? I'm not a nuclear penguin! Could it be kinetic do you you think?
would that be...?
Nowadays, more and more people are using compact fluorescent bulbs or LEDs for lighting because these are much more efficient and don't waste energy producing unwanted heat.

Back to my energy home page

forward to 'Where do we get energy from?.


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