Mr Palmer's AQA GCSE Physics Notes
Power
Generators
The parts of a electrical power station
Most power stations use an electrical generator to create electrical current. The electrical generator needs to rotate to work. In fossil fuel stations and nuclear power stations this is done by the following process:
At A fuels are burnt (or nuclear materials undergo fission) to produce heat. This heat is used to boil water. The steam created then rises and travels through a pipe toward B.
At B this steam is used to rotate a turbine. A turbine is a large fan especially designed to turn easily.
The turbine is connected to the electrical generator at C, causing it to rotate and create electrical current.
The steam is then condensed by a cooling system D and drawn back into the burner at A.
Sources of renewable energy are, in most cases, able to rotate the turbine directly, eliminating the need to burn fossil fuels. Renewable energy means that, for all practical purposes, the source of the energy will not run out.
Fossil Fuels
Fossil fuels include coal, oil and natural gas.
In oil and coal power stations, the fuel is burnt to generate steam which turns a turbine. The burning of natural gas creates a fast jet of hot air that is used to turn a turbine.
Advantages:
- Natural gas power stations can be turned on and off rapidly as the demand for electricity changes.
Disadvantages:
- Burning fossil fuels produce the greenhouse gas, carbon dioxide, that causes global warming.
- Non-renewable source of energy.
Hydroelectric Power
Hydroelectric power involves the construction of a dam at the base of a stream to create a large reservoir of water. This water is then allowed to flow through a small opening in the dam. As the water flows it rotates a turbine connected to an electrical generator.
Hoover Dam, in Nevada.
Hydroelectric plants can also use extra electricity (during non-peak times) to pump water back into the reservoir to be used to generate electricity later during peak times. This process is called pumped storage.
Advantages:
- The power generated by hydroelectric can be quickly varied, depending on the demand at the time.
- Does not release greenhouse gasses once running.
- Renewable source of energy.
Disadvantages:
- The dam impacts the surrounding wildlife. People who live in the area of the reservoir need to be relocated.
Tidal Power
As the high tide comes in, a tidal power station traps the water in a large reservoir. When the tide withdraws, the trapped water is allowed to flow back into the ocean. As it does so, it passes through a turbine connected to a generator, causing it to rotate and create electrical current.
Advantages:
- Dependable source of energy.
- Does not release greenhouse gasses.
- Renewable source of energy.
Disadvantages:
- Impacts local wildlife.
- Construction of the station blocks access to the water way via boats.
- They can visually pollute the landscape.
Wave Power
Wave power uses the up-and-down motion of the waves to rotate an electrical generator and create current. This motion can either directly rotate the generator, or it can indirectly rotate it by using the motion of the air. As water moves upward, it forces air past a turbine. This causes the generator to turn and create electric current. As the water level goes down, this draws air in, once again rotating the turbine.
Advantages:
- Does not release greenhouse gasses.
- Renewable source of energy.
Disadvantages:
- The amount of power produced is dependent on the weather.
- They can visually pollute the coastline.
- They can affect the local marine wildlife.
Wind Power
Wind powers uses the force of the wind to turn large propeller blades. They are connected to a generator and as they rotate create electrical current.
Advantages:
- Does not release greenhouse gasses.
- The maintenance costs are low.
- Renewable source of energy.
Disadvantages:
- They can only be built in windy locations.
- Some people think they visually pollute the landscape.
- They can be noisy.
- Each wind turbine only generates a small amount of electricity, so a large number of them are required to equal a fossil fuel station. This takes up a large amount of land.
Solar Power
Solar cells convert the light from the sun directly into electrical energy. Solar cells are also called photovoltaic cells.
Solar panels convert the light from the sun into heat energy.
Advantages:
- Can be used easily in remote locations.
- They do not directly release pollution.
- Renewable source of energy.
Disadvantages:
- Solar cells can only produce a small amount of electricity.
- The efficiency of solar cells is low so a large area is needed to equal a fossil fuel plant.
Geothermal Power
In some geologically active areas, hot water and steam rise from the ground. This heat is generated by the radioactive decay of elements in the Earth. This can be used to rotate a turbine and generator.
Advantages:
- Does not release greenhouse gasses.
Disadvantages:
- The number of locations where geothermal plants can be built is small.
Nuclear Power
Nuclear power stations split heavy elements such as Uranium to generate electricity. This splitting process is called nuclear fission (Nuclear fission is the only time that spelling counts in the physics GCSE. You must spell it with an `i'.) and it releases a large amount of heat. Uranium is not burned. This heat energy is used to generate steam which will then rotate a turbine. Nuclear power stations have a long start up time.
Advantages:
- Nuclear power stations do not produce greenhouse gasses.
Disadvantages:
- They produce radioactive waste, which needs to be stored for hundreds or thousands of years until it becomes safe.
- The construction of nuclear power stations and the storage of waste is costly.
Physics P1 Topics
Physics P2 Topics
- Motion
- Forces
- Energy
- Static Electricity
- Current Electricity
- Mains Electricity
- Momentum
- Nuclear Physics
Other