OCR 21st Century Science Unit P3b Revision

1
OCR 21st Century Science Unit P3b Revision

• Generating energy

2
Generators (dynamos)
Electricity is convenient because it can be
transmitted over long distances and can be used
in many ways. But how is it generated? We need
to use a generator
Basically, a generator works by spinning a magnet
near a coil of wire. Thats useful, but how do
we get this magnet to keep spinning?
3
Using primary energy sources in power stations
1) A fuel is burned in the boiler
2) Water turns to steam and the steam drives a
turbine
3) The turbine turns a generator if you want
more electricity you have to burn more fossil
fuels
4) The output of the generator is connected to a
transformer
5) The steam is cooled down in a cooling tower
and reused
4
Efficiency of Power Stations
Heat
Heat
Heat
15J
Boiler
Turbine
Generator
100J
50J
5J
85J
35J
30J
Heat
Kinetic
Electrical
5
Nuclear power stations
These work in a similar way to normal power
stations
6
Radioactive Waste - Ionisation
Radiation is dangerous because it ionises atoms
in other words, it turns them into ions by
knocking off electrons
Alpha radiation is the most ionising (basically,
because its the biggest). Ionisation causes
cells in living tissue to mutate, usually causing
cancer.
7
Radioactive Contamination
Simply being irradiated by a radioactive
material doesnt have to be dangerous for
example, we have background radiation around us
all the time. However, being contaminated is
far more dangerous. Consider the example of
Alexander Litvinenko who was poisoned with
polonium-210
Timeline of Events
Video of risks from polonium 210
8
Other ways of generating electricity
9
Wind Power
10
Wave Power
11
Hydroelectric Power
12
The National Grid
Electricity reaches our homes from power stations
through the National Grid
If electricity companies transmitted electricity
at 230 volts through overhead power lines there
would be too much energy loss by the time
electricity reaches our homes. To ensure this
doesnt happen, electricity companies transmit
electricity at higher voltages instead.
13
Which power station?
Type of power station Commiss-ioning costs Running costs (p per KWh) Decommiss-ioning costs Life span (years)
Coal 650 million 4 100 million 40-80
Oil 700 million 12 100 million 40-80
Gas 800 million 6 100 million 30-40
Nuclear 2 billion 3 500 million 30-40

1. Which power station is the most expensive to
   build and why?
2. Give one advantage of coal power stations
3. Why is nuclear fuel cheaper than oil?
4. Overall, which power station is the most
   expensive?

14
Matching supply and demand
15
Solar Panels and Thermal Towers
What are the advantages and disadvantages of
solar power?
16
Using Solar Energy in remote places
17
Geothermal Energy
18
Non-renewable energy sources
Advantages
Disadvantages
Cheap fuel costs
Costs a lot of money to decommission a nuclear
plant
Good for basic demand
Reliable
Fuel will run out
Short start-up time for gas and oil
Pollution CO2 leads to global warming and SO2
leads to acid rain
Nuclear produces little pollution
19
Renewable energy sources summary
Advantages
Disadvantages
Zero fuel costs
Unreliable (except for hydroelectric)
Dont produce pollution
Expensive to build
Hydroelectric is good for a sudden demand
Tidal barrages destroy the habitats of wading
birds and hydroelectric schemes involve flooding
farmland
Solar is good for remote locations (e.g.
satellites)
20
Electricity Supply in the UK
Notice that, due to all these advantages and
disadvantages, we use a variety of sources of
energy in the UK