Generating electricity

Question 1

What are fossil fuels? (4)

Answer 1

The fossil fuels are coal, oil, and natural gas. They were formed from the remains of living organisms millions of years ago and they release heat energy when they are burned. They are non-renewable.

Question 2

Explain how power stations generate electricity from a fossil fuel such as coal. (4)

Answer 2

Coal has a store of chemical energy, and when it is burned that energy is transferred as heat.
The heat energy is used to boil water, with the energy then being stored in the water and steam.
The steam transfers the energy as kinetic energy, which then turns a turbine.
The turbine continues to transfer the energy as kinetic energy, and turns a generator that transfers the kinetic energy into electricity.

Question 3

What are disadvantages of using fossil fuels to generate electricity? (3)

Answer 3

They are non-renewable energy resources and will eventually run out.
Coal and oil release sulfur dioxide into the atmosphere when they burn, which causes breathing problems for living creatures and causes acid rain.
They release carbon dioxide when they burn, which contributes to global warming.

Question 4

What is carbon capture? (3)

Answer 4

Carbon capture and storage is a way to prevent carbon dioxide building up in the atmosphere.
It is a rapidly evolving technology that involves separating carbon dioxide from waste gases.
The carbon dioxide is then stored underground, for example in old oil fields or gas fields such as those found under the North Sea.

Question 5

How can nuclear fuels be used to generate electricity? (3)

Answer 5

The main nuclear fuels are uranium and plutonium, which are radioactive metals.
They release heat energy through nuclear fission reactions (where the nuclei in atoms are split).
The rest of the process is identical to the process using fossil fuels.

Question 6

What are advantages to nuclear fuels?

Answer 6

Unlike fossil fuels, nuclear fuels do not release sulfur dioxide or carbon dioxide.

Question 7

What are disadvantages to nuclear fuels? (3)

Answer 7

Nuclear fuels are non-renewable energy resources.
If there is an accident, large amounts of radioactive material could be released into the environment.
Nuclear waste remains radioactive and is hazardous to health for thousands of years, so it must be stored safely.

Question 8

How can wind be used to generate electricity? (2)

Answer 8

The wind is produced as a result of giant convection currents in the Earth’s atmosphere, which are driven by heat energy from the sun.
This means that the kinetic energy in wind is a renewable energy resource.

Question 9

How do wind turbines work? (3)

Answer 9

Wind turbines use the wind to drive turbines directly.
They have huge blades mounted on a tall tower. The blades are connected to a ‘nacelle’, or housing, which contains gears linked to a generator.
As the wind blows, it transfers some of its kinetic energy to the blades, which turn and drive the generator.

Question 10

What are advantages to wind energy? (3)

Answer 10

Wind is a renewable resource.
There are no fuel costs.
No harmful polluting gases are released.

Question 11

What are disadvantages to wind energy?

Answer 11

Wind farms are noisy and may spoil the view for people living near them.
The amount of electricity generated depends on the amount of wind. If there is no wind, there is no electricity.

Question 12

How can water be used to generate electricity?

Answer 12

Water can be used in a variety of different ways to generate electricity, including waves, tides, and hydroelectric power.

Question 13

How do waves generate electricity? (2)

Answer 13

The water in the sea rises and falls because of waves on the surface.
Wave machines use the kinetic energy in this movement to drive electricity generators.

Question 14

How do tides generate electricity? (3)

Answer 14

Huge amounts of water move in and out of river mouths each day because of the tides.
A tidal barrage is a barrier built over a river estuary to make use of the kinetic energy in the moving water.
The barrage contains electricity generators, which are driven by the water rushing through tubes in the barrage.

Question 15

How does hydroelectric power work? (4)

Answer 15

The water comes from behind a dam built across a river valley.
The water high up behind the dam contains gravitational potential energy.
This is transferred to kinetic energy as the water rushes down through tubes inside the dam.
The moving water drives electrical generators, which may be built inside the dam.

Question 16

What are advantages of using water to generate electricity? (4)

Answer 16

Water power in its various forms is a renewable energy resource
There are no fuel costs.
No harmful polluting gases are produced.
Tidal barrages and hydroelectric power stations are very reliable and can be easily switched on.

Question 17

What are disadvantages of using water to generate electricity? (4)

Answer 17

It has been difficult to scale up the designs for wave machines to produce large amounts of electricity.
Tidal barrages destroy the habitat of estuary species, including wading birds.
Hydroelectricity dams flood farmland and push people from their homes.
The rotting vegetation underwater releases methane, which is a greenhouse gas.

Question 18

How does geothermal power work? (3)

Answer 18

Several types of rock contain radioactive substances such as uranium.
Radioactive decay of these substances releases heat energy, which warms up the rocks.

Geothermal power stations exist in places such as Iceland, California and Italy.

Question 19

How do volcanic areas generate electricity? (2)

Answer 19

In volcanic areas, the hot rocks may heat water so that it rises to the surface naturally as hot water and steam.
Here the steam can be used to drive turbines and electricity generators.

Question 20

How do hot rocks generate electricity? (4)

Answer 20

In some places, the rocks are hot, but no hot water or steam rises to the surface.
In this situation, deep wells can be drilled down to the hot rocks and cold water pumped down.
The water runs through fractures in the rocks and is heated up.
It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators.

Question 21

What are advantages to geothermal power? (3)

Answer 21

Renewable energy resource.
No fuel costs.
No harmful polluting gases released.

Question 22

What are disadvantages to geothermal power?

Answer 22

Most parts of the world do not have suitable areas where geothermal energy can be exploited.