Topic 8: Energy, Climate and Power

Question 1

Degraded energy

Answer 1

Energy which is spread out or disordered. The most

degraded form of energy is thermal energy. Not able to be used for useful work.

Question 2

Entropy

Answer 2

A measure of disorder of a system

Question 3

Second law of thermodynamics

Answer 3

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.

Question 4

Sankey diagrams

Answer 4

Energy flow diagrams whose dimensions also give a

measure of the proportions of the different types of energy.

Question 5

Electromagnetic induction

Answer 5

When the magnetic field cutting a conductor

changes, a voltage is induced in the conductor.

Question 6

Generator

Answer 6

A rotating coil in a magnetic field (or field rotating about a coil)
produces an alternating voltage by electromagnetic induction.

Question 7

Renewable energy sources

Answer 7

Sources which will not be exhausted over

time.

Question 8

Fossil fuels

Answer 8

Oil, gas, coal made over millions of years from plants and
organisms. Nonrenewable.
Produce CO2 when burned.

Question 9

Nuclear chain reactions

Answer 9

Nuclear fission produces neutrons. If one neutron

can produce, on average, one other fission, there will be a chain reaction.

Question 10

Critical mass

Answer 10

The mass of fissile material needed to sustain a fission reaction.

Question 11

Moderator

Answer 11

A material which slows down fast neutrons to KE of 1eV. Necessary
for nuclear fission. Examples: graphite, water

Question 12

Control rods

Answer 12

Material which absorbs neutrons. Used to control chain reaction.
Example: Boron

Question 13

Uranium

Answer 13

Naturally occurring uranium contains 99.3% U238

Question 14

Fuel enrichment

Answer 14

Process to raise proportion of U235
in nuclear fuel from
0.7% to 3%.

Question 15

Plutonium

Answer 15

Byproduct of uranium fission. Can be used in another type of nuclear reactor or in nuclear weapons.

Question 16

Nuclear meltdown

Answer 16

Uncontrolled nuclear reaction due to failure of control

rods or cooling cause overheating of nuclear core and melting of fuel rods.

Question 17

Nuclear fusion

Answer 17

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.

Question 18

Solar constant

Answer 18

Intensity (power per unit area) of the Sun (1380 Wm2).

Question 19

Photovoltaic cell

Answer 19

Converts solar radiation into electrical energy.

Question 20

Solar heating panel

Answer 20

Water flows in pipes and is warmed by the Sun.

Question 21

Hydroelectric power

Answer 21

Downward flowing water converts gravitational PE to

electrical energy. Uses dams, fast rivers, pumps or tides.

Question 22

Wind power

Answer 22

Turbines are rotated by the KE of moving air to generate electricity.

Question 23

Wave power

Answer 23

Energy in water waves converted, for example by water oscillating in a column.

Question 24

Albedo

Answer 24

The ratio of reflected to incident light. Snow 90%; dark ground: 10%.
Earth’s average: 30%.

Question 25

Greenhouse effect

Answer 25

The Earth’s atmosphere is warmed by absorbing some of

the infra-red radiation emitted by the ground.

Question 26

Greenhouse gases

Answer 26

Gases in the atmosphere which absorb heat radiation. Eg

carbon dioxide, methane, water vapour

Question 27

Resonance

Answer 27

A molecule can absorb radiation energy if it has the same natural frequency of oscillation as the photon.

Question 28

Gas absorption

Answer 28

Different gases absorb different frequencies of radiation

depending on their chemical bonds. Ozone absorbs UV; CO2 absorbs IR.

Question 29

Blackbody radiation

Answer 29

A theoretical body which absorbs and emits all wavelengths of EM radiation. The graph is characteristic and its peak varies with temperature of the body.

Question 30

Stefan-Boltzmann Law

Answer 30

Relation of power per unit area (Wm2) to temperature (K). Stefan-Boltzmann constant, σ = 5.67*1^08

Question 31

Emissivity

Answer 31

How much energy a body radiates compared to a black body.

Question 32

Surface heat capacity

Answer 32

The amount of heat, required to raise the temperature

of 1 m2 of a surface by 1 K. eg Earth: 4*108 Jkm^-2K^-1

Question 33

Global warming

Answer 33

The result of more solar radiation or less reradiating from Earth.

Question 34

Enchanced greenhouse effect

Answer 34

Greenhouse effect due to human activities, increases amount of greenhouse gases.

Question 35

Combustion of fossil fuels

Answer 35

Produces CO2, a greenhouse gas. Likely to be

causing heating of the Earth.

Question 36

Ice cores

Answer 36

Long cylinders of ice from Antarctica are analysed and show a close correlation between Earth’s temperature and CO2 levels.

Question 37

Coefficient of volume expansion

Answer 37

A measure of how volume of a liquid changes with temperature. They are proportional. Unit: K^-1

Question 38

Energy density

Answer 38

Amount of energy stored in a given system per unit mass