Studied by 4 people
Emissivity
The ratio of actual power emitted to power emitted by a black body
Albedo
The ratio of reflected intensity/power to incoming intensity/power.
thermal radiation
emission of (infrared) electromagnetic/infrared energy/waves/radiation
Mechanism of infrared absorption of greenhouse gases
Molecules of greenhouse gases have energy levels and their energy level differences correspond to infrared photon energy → molecules are good at absorbing and re-emits back to Earth’s surface
Without greenhouse gases, less infrared is absorbed and trapped, so less infrared is re-radiated to Earth, hence the Earth’s surface is less heated up and its surface temperature decreases
Why fuel enrichment is necessary for the fuel used in a commercial nuclear reactor
U-235 is more fissionable than U-238
Naturally occurring uranium ore contains more U-238 atoms than U-235 atoms
In fuel enrichment, U-238 is removed, increasing the concentration of U-235
Outline, with reference to the speed of the neutrons, the role of the moderator in a nuclear reactor
Neutrons emitted from uranium at high speed
High-speed neutrons do not cause fission
Neutrons collide with moderator atoms
Therefore lose energy/speed before re-entering fuel rods
Distinguish between a solar heating panel and a photovoltaic cell
Solar heating panel convert radiation energy of the Sun directly into thermal/heat energy
Photovoltaic cells convert into electrical energy
Outline, with reference to energy changes, the operation of a pumped storage hydroelectric system
PE of water is converted to KE of moving water/turbine to electrical energy in generator/turbine/dynamo
Water is pumped back up when the demand for and prices of electricity is low, then water is released and hydroelectricity is generated when the demand for and prices of electricity is high → make a profit
Mechanism of wind turbines
kinetic energy of wind transferred to (rotational) kinetic energy of turbine/blades
kinetic energy is changed to electrical energy in a generator/dynamo
(Generator/dynamo must be mentioned)
Mechanism of nuclear power production
KE of fission fragments → nuclear energy → thermal energy of the coolant/water/steam
Thermal energy → KE or (rotating) magnets/coils/turbines/generators → electrical energy
Mechanism of coal-fired/fossil fuel power production
Burning gas
Internal energy/KE of steam/particles transfers to KE of turbine, which transfers to KE of generator/dynamo producing electrical energy
Wind Turbines Advantages
wind is renewable so no resources used up
wind is free
no chemical pollution
no carbon dioxide emission
does not contribute to greenhouse effect
Is “scalable” i.e. many sizes of turbine possible
Wind Turbines Disadvantages
expensive initial cost
large land area needed
wind not constant
effect on movement of birds
aesthetically unpleasant
noise pollution
high maintenance costs
best locations far from population centres
low energy density
Nuclear power production Advantages
Nuclear power does not produce carbon dioxide → does not add to global warming
Energy density of U-235 (fuel) is very high/small mass is required → fuel likely to last a long time/easier to transport
Nuclear power production Disadvantages
Accidents are potentially catastrophic → leading to widespread cancers
Allows the development of nuclear weapons like dirty bombs
Waste products of U-235 are radioactive → no safe method of disposal
Power plant is more expensive because of eg. safety measures, decommissioning, etc.
Coal-fired/fossil fuel power production Advantages
No radioactive waste
No radiation risks to users
Easier to install/lower cost of decommissioning
Safer transportation and storage
Simpler technology
Cannot be used for military purposes
Fossil fuels can be found/extracted more easily
No chance of meltdown/catastrophic accident/Chernobyl
Plentiful supplied at present
Pre-existing infrastructure
Easily portable, easily mined
Coal-fired/fossil fuel power production Disadvantages
Contributes to greenhouse effect
Non renewable → will run out
Note
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