Electricity is hard to explain because it is something we cannot see. It is unlikely that anyone will ever properly see electricity because the electrons, which it is made of, are so small. Electricity truly is an 'invisible force'.

But we can see what electricity does - the results of electricity's power - and we can understand it best by understanding how it is made and how it is used.

Everything in the world is electrical because all matter in the world - including the human body - is made up of atoms, and every atom is made up of a number of electrons and protons which are 'particles' of electricity. Once we have generated electricity we can make it do almost anything for us.

How do electricity generators work?

We say that electricity is 'made' by a generator. But it is important to realise that a generator does not actually 'make' electricity but simply changes one form of energy - for example the power of steam, or moving water - into another form of energy called electricity.

We generate electricity because although there is plenty of energy in steam or moving water we cannot use that energy to light our homes or power our television sets.

Generators can be very small or very large. But, whatever their size, they all work on the same principle which was discovered in 1831 by the English physicist, Michael Faraday. Faraday found that he could produce electricity in a coil of copper wire by moving it near a magnet. When this happens very quickly - when a loop of copper wire is spun between the north and south poles of a magnet - electricity is said to be 'induced' in the wire.

The machines in power stations that are used to drive the electrical generators are called turbines. The turbines must be turned by some existing energy which the generator will convert to electricity and send down the cables to houses, factories and offices that are hundreds or thousands of kilometres away from the original source of energy.

An example of hydro power generation

There are three main sources of natural energy that can be used to turn generator turbines. They are known as primary, recurring and non-renewable sources of energy.

1. The primary sources are thermonuclear reaction, nuclear fission and radioactivity.
    
2. The recurring sources include solar energy, natural thermal energy, wind and moving water.
    
3. Non-renewable sources include natural gas, coal and oil (fossil fuels).

Of the three main sources of natural energy used to turn turbines, water is used the most in New Zealand. Some electricity is also produced from thermal energy and from the non-renewable sources of natural gas, coal and oil. No electricity in New Zealand is produced from primary sources such as thermonuclear reaction and nuclear fission.

Who generates electricity in New Zealand?

There are a number of electricity generators in New Zealand. The company which owns Mercury Energy, called Mighty River Power, is one of them. Mighty River Powers' generation strength comes mostly from nine hydro stations on the 425 kilometre long Waikato River.