P8.2 Flashcards
What are the 3 fossil fuels
Coal + oil + gas
How are fossil fuels formed
They are formed from the remains of once living animals and/or plants.
What do we use fossil fuels for
We use fossil fuels for generating electrical energy
electricity
Define renewable energy
A renewable energy source is one that is not used up in releasing energy, so can be used again.
What is a non - Renewable energy source
A non-renewable energy source that is used up in releasing energy and will eventually run out.
Example of renewable energy - 3
Solar – energy from the sun’s light.
Wind – energy from the wind’s movement.
Geothermal – energy from the Earth’s heat.
How do power plants work
Advantages of fossil fuel power plants
- relatable source of energy
- cost effective / safe
Disadvantages of fossil fuel power plants work
- emits greenhouse gases
- non renewable
What is the greenhouse effect
The Greenhouse Effect is the process by which the Earth’s atmosphere traps the Sun’s heat.
How do nuclear power plants work
Nuclear power plants work in the same way as conventional power plants…
… water to steam to turbine … etc.
BUT
- in a nuclear power plant, no fuel is burnt.
- Instead the heat required to turn water to steam comes from NUCLEAR FISSION reactions.
Advantages of nuclear power plants
- lots of energy per kg (more than fossil fuels)
- no greenhouse gases
Disadvantages of nuclear power plants
- radioactive waste is difficult to dispose of
- NON RENEWABLE
- potentially very dangerous
Define biofuel
A biofuel is a fuel obtained from living (or recently living) organisms.
Examples of biofuels
Methane - gas from cows or manure
Ethanol - from sugar cane
Major advantage of biofuels
Biofuels are CARBON NEUTRAL…
… the CO2 released in burning biofuels,is reabsorbed when a new crop of plants is grown.This ensures there is no net increasein the amount of CO2 in the atmosphere.
Compare Renewable and non - renewable energy sources
- Renewable energy sources can be used to generate energy over again, without running out.
- Non-renewable energy sources will eventually run out.
- Renewable energy sources such as solar and geothermal, don’t 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.
Suggest and explain what might happen to the behaviour of individuals and governments as fossil fuels begin to runout
As fossil fuels begin to run out, the cost of fuel for cars and electricity will start to increase.
Individuals will be/are encouraged to think about their energy use, and to be mindful not to use energy unnecessarily.
For example, turn off the lights in rooms you are not using.
In order to continue to meet demand for electricity, Governments will need to invest money in developing renewable sources of energy.
Although initially expensive to build, in the long term renewable sources of energy will ensure electricity generation remains cost effective and affordable.
Define the national grid
is a network of cables and pylons, that carry electricity generated in Power Plants to homes and businesses.
What’s the role of transformers in the national grid
Transformers are used to adjust the voltage (therefore the current) to minimise power/energy loss as heat.
What do step up transformers do
STEP-UP TRANSFORMERS
Increase the voltage…
∴ decrease current in wires
=> less energy lost as heat
What do step down transformers do
STEP-DOWN TRANSFORMERS
Decrease the voltage…
∴ increase current in wires
=> appliances at home can run without 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
- each electron carries more energy
- fewer electrons needed to carry the energy
- fewer collisions in wire between electrons andwire atoms
- less heat energy wasted
How does increasing the voltage decrease energy loss
- higher voltage
- each electron carries more energy
- fewer electrons needed to carry the energy
- fewer collisions in wire between electrons andwire atoms
- less heat energy wasted
Transformer power equation
Explain why the power lines supported by the 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 a high likelihood of current arcing to the ground.
Explain why need to use transformers in the national grid (4 marks)
Current in wires wastes energy by transferring some electrical energy as heat to the surroundings.
In order to reduce this energy loss, electricity is transferred at high voltages in the cables of the National Grid.
Increasing the voltage of the electrical energy, reduces the current.
Transformers are used to step-up the voltage after a power plant and to step-down the voltage before homes/businesses.
Define direct current
Electric current which flows in one direction only in a circuit.
[provided by cells and batteries]
Define alternating current
Electric current which repeatedly alternates direction in a circuit.
[provided by mains]
AC FREQUENCY IN THE UK
50Hz
When the current of an AC supply changes directions…
the voltage changes directions.
What is the peak voltage in the UK
310 V
The AVERAGE VOLTAGE IN THE UK - KNOW THIS
240V
What is the live wire
Current enters appliance through live wire.
p.d. between ground and live wire = 240V
What is the neutral wire
Current leaves appliance through neutral wire.
p. d. between ground and neutral wire = 0V
(p. d. between live and neutral wire = 240V)
What is the earth wire
In the event of a fault, current directed safely to ground through Earth wire.(p.d. between ground and Earth = 0V)
(p.d. between live and Earth = 240V)
Colour of the live wire
Brown
Colour of the neutral wire
Blue
Colour of the earth wire
Yellow + green pattern
How does the earth wire save lives
Earth wire is connected to the ground at your house.
Longest pin of plug makes contact with earth wire in your house.
When anything with a metal case is plugged in…… automatically grounded.
If a fault occurs in an appliance and electrons end up in the metal case…
… they will travel safely into the ground through the Earth wire (instead of through a person, electrocuting them)
What is the difference between a 3- core cable and a 2-core cable
3-core cables contain the live, neutral and earth wires.
2-core cables contain only the live and neutral wires.
Why do some appliances not need the earth wire
Appliances that have a PLASTIC case do not require an earth wire…
- they are said to be DOUBLE insulated
+ and have 2-core cables attached.
Suggest why the earth pin of a plug for a hairdryer with a plastic casing, is also made of plastic
Plastic is an insulator.
If a fault occurs in a hairdryer, there is no danger of the current being conducted into a person.
Hence, a hairdryer is said to be double insulated and does not require an Earth wire.
Explain why the p,d from the national grid is alternating and not direct
The National Grid uses transformers to increase and decrease the potential difference of the mains supply.
This is to reduce energy loss during transmission of electricity through the National Grid power lines.
Transformers can only function using alternating current.
