The National Grid

Question 1

Fill in the blank.

Electricity in South Africa is generated from sources such as ____, _____, _____, ______ _____, ______ ____, and _____.

Answer 1

Coal, gas, oil, falling water, nuclear fuels, and wind.

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Question 2

Fill in the blank.

Approximately ___% of all energy in SA comes from burning coal in power stations.

Answer 2

95%

Question 3

Fill in the blank.

The electricity formed by the fuels is fed into the _____km of cables in the _________ _______ ____.

Answer 3

27000

National electricity grid

Question 4

How is energy produced? Name step 1.

Answer 4

In all power stations, energy produced from coal, falling water, oil, gas, nuclear fuels and wind is transferred to make large turbines rotate. Turbines look like giant fans with large metal blades.

Remember: TURBINES

Question 5

How is energy produced? Name step 2.

Answer 5

Mechanical energy from the movement of the turbine is transferred into a generator, where it is converted to electrical energy.

Remember: GENERATOR

Question 6

How is energy produced? Name step 3.

Answer 6

The freshly made electricity is transferred via the cable of the national electrical supply system to our homes and businesses.

Remember: CABLE

Question 7

Name the first five parts of a coal-fired power station.

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Answer 7

1. Coal- the fuel used to make electricity.
2. Furnace- the potential energy of the coal is released by burning the coal. The burning coal heats the water in the boiler (heat energy is transferred from the burning coal to the water).
3. Boiler- In the boiler, heat from the burning coal heats up pipes full of cold water. The heat boils the water and turns it into steam.
4. Turbine- the steam flows around the turbine and makes the blades of the turbine turn. The heat energy is transferred into mechanical energy.
5. Cooling tower- the large cooling towers make the turbine more efficient. Boiling hot water from the steam turbine is cooled and then sprayed into the giant cooling towers where it is then pumped back to the boiler for re-use. Some of the water escapes from the tower as steam so large amounts of energy are lost at this point.

Question 8

Name the second five parts of a coal-fired power station.

GEPHA

Answer 8

6. Generator- the turn is connected to the generator via a long shaft. In the generator, mechanical energy from the turbine is transferred into electrical energy which is fed into the electrical cables.
7. Electricity cables- the electricity produced by the generator is transferred into the cables of the national electricity supply grid.
8. Pylons- large metal towers carry electricity via overhead cables to wherever it is needed.
9. Homes- underground electricity cables deliver electricity to our homes.
10. Appliances- electricity is available in our homes when we plug appliances into the plug sockets in the walls.