ENERGY

After you have run around you feel tired.
A car needs petrol to make it move.
Calculators won’t work without a battery or sunlight.
A hurricane can cause great damage to a countryside.
When we burn some coal it gives out heat.
The electricity board has built some big windmills to make electricity

All these are examples of the use and effects of different types of ENERGY.

What is energy? In Physics we say that energy is the thing that is needed to make things happen. Without energy nothing would happen at all and the world would did
Energy is measured in units called JOULES. We will see exactly what a joule is later on but it would be useful to get an idea of how much energy different things use or need.

Activity	Energy used (Joules)
Moonlight on your face for one second	1 thousandth
Pressing down a computer keyboard key	1
Lifting a 1kg bag of sugar up 1 m	10
Burning one match	10 000
Lorry at speed for one second	10 million
Daily need for a 15 year old boy	15 million
100 m diameter windmill per second	30 million
Output of a power station per second	1000 million
First atomic bomb	100 million million
Hurricane	1000 million million
Severe earthquake	100 million million million
Solar energy falling on the Earth per year	100 million million million million

SOURCES OF ENERGY

All the energy on Earth came originally from the Sun.
Today there are a number different places where we can get energy from.
We call these ENERGY SOURCES

We can get energy from:

The Sun cheap and easy if it's sunny. Solar energy will become very useful in hot sunny areas of the world.

Fossil fuels Coal, Oil and Gas
The trouble is that they will not last for ever. The world has about 400 years supply of coal but only about fifty years supply of both oil and gas.

Wood quite a lot of energy can be made from wood by turning it into gas first. People in Scandinavia have been trying to do this.
Wind using modern windmills this is a good idea. The trouble is that they must be put in very windy places to be useful. These are often far away from where the most of the energy is needed.

Microbes bacteria can be used to digest waste and give off methane gas which can be used as a fuel.

Water you can get energy from water in three ways
(a) Waves - this is possible only where you have really big waves. Getting the energy from such areas to where it is needed is very expensive.

(b) Tides - building a tidal barrage across a river estuary has been used in France to produce energy and a large barrage may be built across the Severn estuary in South West England.

(c) Hydroelectricity - this is made when water falls down a mountainside. This method of getting energy from water is only useful in hilly areas where there is a lot of rainfall or in large dams on rivers. The energy from the moving water is used to turn a water wheel or a turbine.


Geothermal As you go down below the surface of the Earth it starts to get warmer. In some areas of the world such as New Zealand and parts of the USA and Italy steam actually shoots out of the ground as geysers. In other places the heat from below ground is not so great but it is still used to provide hot water for housing estates. The photo shows pipes emerging from the ground at Lardarello in Tuscany.



Nuclear nuclear energy in the form of nuclear fission reactors is already in use in many parts of the world. Nuclear fusion - the energy that powers the stars - is not likely to be possible on this earth until the middle of the next century.

STUDENT INVESTIGATION
Which of these energy sources do you think would be the best for making electricity?
Explain your answer.

Renewable and non-renewable sources of energy
Sources of energy are either RENEWABLE or NON-RENEWABLE.


Some of these, like the fossil fuels, will run out sooner than others if we go on using them at the rate at which we are today.

TYPES OF ENERGY

These energy sources may be used to produce many TYPES of ENERGY

These energy types are:
Motion (Kinetic) Heat Position (Potential) Light Magnetic Chemical Electrical Sound (really motion) Nuclear Animal (really chemical) Stored (as in a spring or as gas pressure)

CONSERVATION OF ENERGY

It is a very important law of Physics that you can't get energy out of nothing. For example if you want to make some light energy then another sort of energy has to be used up. This is called the LAW OF CONSERVATION OF ENERGY. Written another way it is:

Energy cannot be created or destroyed – only changed from one form to another.

When one form of energy is changed into another we call this an ENERGY CHANGE.

Some examples of energy changes are:
1. a candle burning - chemical energy changes to heat and light energy
2. an electric motor - electrical energy changes to motion energy (and a little sound and heat)

QUESTIONS
Write down the energy changes for the following:
1. A match burning
2. A girl running uphill
3. A plant growing in the garden
4. An electric torch shining
5. Winding up a spring powered watch
6. A grandfather clock working