Topic 8: Energy, Climate and Power Flashcards
Degraded energy
Energy which is spread out or disordered. The most
degraded form of energy is thermal energy. Not able to be used for useful work.
Entropy
A measure of disorder of a system
Second law of thermodynamics
heat always flows spontaneously from hotter to colder bodies, and never the
reverse, unless external work is performed on the system
● the entropy of an isolated system never decreases, because isolated systems always evolve toward thermodynamic equilibrium, a state with maximum entropy.
Sankey diagrams
Energy flow diagrams whose dimensions also give a
measure of the proportions of the different types of energy.
Electromagnetic induction
When the magnetic field cutting a conductor
changes, a voltage is induced in the conductor.
Generator
A rotating coil in a magnetic field (or field rotating about a coil)
produces an alternating voltage by electromagnetic induction.
Renewable energy sources
Sources which will not be exhausted over
time.
Fossil fuels
Oil, gas, coal made over millions of years from plants and
organisms. Nonrenewable.
Produce CO2 when burned.
Nuclear chain reactions
Nuclear fission produces neutrons. If one neutron
can produce, on average, one other fission, there will be a chain reaction.
Critical mass
The mass of fissile material needed to sustain a fission reaction.
Moderator
A material which slows down fast neutrons to KE of 1eV. Necessary
for nuclear fission. Examples: graphite, water
Control rods
Material which absorbs neutrons. Used to control chain reaction.
Example: Boron
Uranium
Naturally occurring uranium contains 99.3% U238
Fuel enrichment
Process to raise proportion of U235
in nuclear fuel from
0.7% to 3%.
Plutonium
Byproduct of uranium fission. Can be used in another type of nuclear reactor or in nuclear weapons.
Nuclear meltdown
Uncontrolled nuclear reaction due to failure of control
rods or cooling cause overheating of nuclear core and melting of fuel rods.
Nuclear fusion
How the Sun produces energy. Joining of two light nuclei
which releases energy. Requires high density
plasma at extremely high temperatures
contained by magnetic fields. Not yet commercial.
Solar constant
Intensity (power per unit area) of the Sun (1380 Wm2).
Photovoltaic cell
Converts solar radiation into electrical energy.
Solar heating panel
Water flows in pipes and is warmed by the Sun.
Hydroelectric power
Downward flowing water converts gravitational PE to
electrical energy. Uses dams, fast rivers, pumps or tides.
Wind power
Turbines are rotated by the KE of moving air to generate electricity.
Wave power
Energy in water waves converted, for example by water oscillating in a column.
Albedo
The ratio of reflected to incident light. Snow 90%; dark ground: 10%.
Earth’s average: 30%.
