P8.2 - Powering Earth Flashcards
What are the differences between renewable and non-renewable energy?
Renewable energy can be produced and supplied at the rate it is being used and hence will not run out. However, non renewable sources of energy will eventually run out as they take a very long time to form and cannot be supplied at the rate they are being used up in.
Renewable energy sources such as solar and geothermal generate greenhouse gases do not generate greenhouse gases nor nuclear radiation.
Therefore, renewable energy sources don’t give rise to environmental problems such as global warming.
However, unlike non-renewable sources of energy, renewable sources of energy such as solar and wind, are unreliable.
How do fossil fuel power plants work?
You burn fossil fuels such as coal, oil and gas.
The energy released heats water to make steam.
The steam turns a turbine.
The turbine turns a generator and electricity is produced.
What is the difference between nuclear power plants and conventional power plants?
The heat required to turn the water to steam comes from nuclear fission reactions and not burning fossil fuels.
What are the advantages and disadvantages of fossil fuels power plants?
Advantages
- Cost effective
- Reliable source of energy
Disadvantages
- The burning of fossil fuels releases greenhouses gases
- Fossil fuels are non-renewable
What are the advantages and disadvantages of nuclear power plants?
Advantages
- Lots of energy per kg than fossil fuels
- No greenhouse gases produced
Disadvantages
- Radioactive waste is difficult to dispose of
- It is potentially very dangerous
What are biofuels?
Biofuels are fuels that are obtained from living (or recently living) organisms.
How are biofuels carbon neutral?
Biofuels are carbon neutral because the carbon dioxide released in burning biofuels is reabsorbed when a new crop of plants is grown.
This ensures that there is no net increase in the amount of carbon dioxide in the atmosphere.
What are the two different types of ‘solar panels’?
Solar panels - Light energy to heat energy Solar cells (photovoltaic cells) - Light energy to electrical energy
What energy sources are used for heating?
- Fossil fuels
- Biofuels
- The sun
- Water pumped into hot rock
What energy sources are used for transportation?
- Fossil fuels
- Biofuels
What energy sources are used for generating energy?
- Fossil fuels
- Biofuels
- Nuclear fuel
- Solar power
- Tidal power
- Wind power
- Wave power
- Geothermal power
- Hydroelectric power
Why has our use of energy sources changed over time?
There has been an increase in:
- Population
- The use of devices that use fuels
- Energy generation
What do individuals or governments need to consider when deciding which energy sources to use?
Cost (to set up, and to remove)
Effect on the environment (pollution, how it looks if you live nearby)
Contribution to climate change.
How long the sources will last.
What is The National Grid?
The National Grid is a network of cables and pylons, that transfer electrical energy generated in power plants to homes and businesses.
Why are transformers used in the national grid?
The electricity has to be transferred over long distances. This electrical power can be subject to a lot of loss as heat, if the current is high.
Transformers are used to adjust the voltage (therefore the current) to minimise power/energy lost as heat.
What is the purpose of step-up transformers?
Increase the voltage and hence decrease the current in the wires. This results in less energy lost as heat.
What is the purpose of step-down transformers?
To decrease the voltage and hence increase the current in the wires. This results in appliances being able to be run at home without any problems.
Why is electricity transferred through The National Grid at a much higher voltage than the voltage generated in a power station?
In order to reduce energy loss as heat.
Higher voltage results in each electron carrying more energy.
Subsequently there is a reduced current as this means that fewer electrons are needed to carry the energy which results in fewer collisions in the wire between the electrons and the wire atoms.
This in turn means that less heat energy is wasted.
What is the transformer power equation?
Power in primary circuit = Power in secondary circuit
Current in primary circuit x Potential difference in primary circuit = Current in secondary circuit x Potential difference in secondary circuit
Explain why the power lines supported by pylons have to be so high off the ground?
The power lines are at a high potential difference, with respect to the ground, and so there is high likelihood of current arching to the ground.
What is the equation to calculate the efficiency of a transformer?
Efficiency of transformer = Power out (in secondary circuit) / Power in (in primary circuit)
What is the domestic supply?
The electrical supply that we use in homes and businesses, which is AC and has a potential difference of 230V and 50Hz.
What is the voltage for any appliance with a battery?
A direct voltage.
A potential difference that does not change direction.
What does a UK plug have?
A UK plug has three pins which are connected to three different wires inside the socket in your wall.
What does the live wires and neutral wires do in a plug?
The live wire (brown) and the neutral wire (blue) are two wires that make a complete circuit with the appliance.
What does the earth wire do in a plug?
The earth wire (green and yellow) is not connected to the mains.
It is connected to the ‘earth’ which is usually a large metal pole buried in the ground outside your house.
What happens if the live wire in an appliance becomes loose?
It can touch a metal casing, and we can say the casing is live.
If you touch the casing there is a potential difference of 230V across you because you are connected to the earth.
A dangerous current can flow through you.
How is a dangerous current flowing through you when a live wire becomes loose prevented?
The earth wire connects the case to the pole in the ground so that current flows through the earth wire and not through you.
The earth wire has less resistance than you.
The wire inside the fuse also melts and switches of the circuit.
The appliances are also ‘double insulated’ (the wires and the plastic case) - So no current can flow through the case to you.
