P1.4 Methods we use to generate electricity

AQA GCSE Science A

Various energy sources can be used to generate the electricity we need. We must carefully consider the advantages and disadvantages of using each energy source before deciding which energy source(s) it would be best to use in any particular situation. Electricity is distributed via the National Grid.

Candidates should use their skills, knowledge and understanding to:

■ evaluate different methods of generating electricity■ evaluate ways of matching supply with demand, either by increasing supply or decreasing demand■ compare the advantages and disadvantages of overhead power lines and underground cables.

P1.4.1 Generating electricity

a) In some power stations an energy source is used to heat water. The steam produced drives a turbine that is coupled to an electrical generator.

Energy sources include:■ the fossil fuels (coal, oil and gas) which are burned to heat water or air■ uranium and plutonium, when energy from nuclear fission is used to heat water■ biofuels that can be burned to heat water.

b) Water and wind can be used to drive turbines directly.

P1.4.1 Generating electricity

c) Electricity can be produced directly from the Sun’s radiation.

P1.4.1 Generating electricity

d) In some volcanic areas hot water and steam rise to the surface. The steam can be tapped and used to drive turbines. This is known as geothermal energy.

P1.4.1 Generating electricity

e) Small-scale production of electricity may be useful in some areas and for some uses, eg hydroelectricity in remote areas and solar cells for roadside signs.

P1.4.1 Generating electricity

f) Using different energy resources has different effects on the environment. These effects include:• the release of substances into the atmosphere• the production of waste materials noise and• visual pollution the destruction of wildlife

habitats.

P1.4.1 Generating electricity

P1.4.2 The National Grid

a) Electricity is distributed from power stations to consumers along the National Grid.

There are four main stages:the fuel is burned to boil water to make steamthe steam makes a turbine spinthe spinning turbine turns a generator which produces electricitythe electricity goes to the transformers to produce the correct voltage

P1.4.2 The National Grid

b) For a given power, increasing the voltage reduces the current required and this reduces the energy losses in the cables.

P1.4.2 The National Grid

c) The uses of step-up and step-down transformers in the National Grid.

A transformer is an electrical device that changes the voltage of an alternating current (ac) supply, such as the mains electrical supply. A transformer changes a high-voltage supply into a low-voltage one, or vice versa.A transformer that increases the voltage is called a step-up transformer.A transformer that decreases the voltage is called a step-down transformer.

1. Why are coal, oil and natural gas non-renewable resources?

A They contain carbon compounds.B They cannot be replaced, except over millions of years.C Once used, they cannot be used again.

1. Why are coal, oil and natural gas non-renewable resources?

A B They cannot be replaced, except over millions of years.C

2. For a given amount of energy released, which fuel releases the most carbon dioxide?

A CoalB OilC Natural gas

2. For a given amount of energy released, which fuel releases the most carbon dioxide?

A CoalB C

3. Which type of power station takes the least time to start up?

A Gas-fired power stationB Nuclear power stationC Coal-fired power station

3. Which type of power station takes the least time to start up?

A Gas-fired power stationBC

4. What problem does sulfur dioxide cause?

A It contributes to global warming.B It harms the ozone layer.C It contributes to acid rain.

4. What problem does sulfur dioxide cause?

A BC It contributes to acid rain.

5. Why are uranium and plutonium used as nuclear fuels?

A They are metals.B They release a lot of heat when they burn.C They are radioactive.

5. Why are uranium and plutonium used as nuclear fuels?

ABC They are radioactive.

6. Which of the following is an advantage of nuclear fuels?

A They are renewable energy resources.B They do not emit harmful radiation.C They do not produce greenhouse gases.

6. Which of the following is an advantage of nuclear fuels?

ABC They do not produce greenhouse gases.

7. Which of the following is a disadvantage of wind farms?

A They use a renewable energy resource.B They are noisy and unsightly.C They do not produce electricity at night.

7. Which of the following is a disadvantage of wind farms?

A B They are noisy and unsightly.C

8. Which of the following is a disadvantage of hydroelectric power produced by using a dam?

A The power station only works when the tide comes in.B River valleys and farmland are flooded by the dam.C The power station only works on rainy days.

8. Which of the following is a disadvantage of hydroelectric power produced by using a dam?

A B River valleys and farmland are flooded by the dam.C

9. Where does the heat energy for geothermal energy resources come from?

A From radioactive decay in rocksB From hot water and steam in the power stationC From the Sun warming the ground

9. Where does the heat energy for geothermal energy resources come from?

A From radioactive decay in rocksBC

9. Where does the heat energy for geothermal energy resources come from?

A From radioactive decay in rocksB From hot water and steam in the power stationC From the Sun warming the ground

10. Which of the following is a disadvantage of solar cells?

A They can supply electricity in remote areas.B They do not produce electricity at night.C They need complex moving parts.

10. Which of the following is a disadvantage of solar cells?

A B They do not produce electricity at night.C

Label and identify parts of the national grid

Why are transformers an important part of the national grid?