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IB Physics > Energy Production > Flashcards

Energy Production Flashcards

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1
Q

primary energy

A

energy found in nature that has not yet been subject to processing of any kind

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2
Q

examples of primary energy

A
  • energy stored in fuels (crude oil, coal, natural gas)
  • solar energy, wind energy
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3
Q

secondary energy

A

primary energy that has been processed or exploited

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4
Q

specific energy

A
  • ES
  • amount of energy that can be extracted from a unit mass of fuel
  • Jkg-1
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5
Q

energy density

A
  • ED
  • amount of energy that can be extracted from a unit volume of fuel
  • Jm-3
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6
Q

non-renewable sources of energy

A
  • finite sources being depleted much faster than they can be produced and so will run out
  • e.g. fossil fuels, nuclear fuels
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7
Q

renewable sources of energy

A
  • solar, wind, wave energy
  • tidal energy
  • are indefinitely available
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8
Q

fossil fuels

A

produced by decomposition of buried animal and plant matter under combined action of high pressure of material on top and bacteria

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9
Q

coal-burning power plant

A
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10
Q

How does a coal-burning power plant work?

A
  1. burning coal produces energy
  2. powers boilers that turns water into steam
  3. pressurized steam forces turbine to turn
  4. turbine makes coils of generator rotate in a magnetic field
  5. electricity created by electromagnetic induction
  6. cold water condenses steam into liquid to be used again
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11
Q

sankey diagram

A
  • arrow block diagram representing energy flow
  • width of arrow proportional to amount of energy being transferred
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12
Q

efficiency equation

A

e = useful power/input power

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13
Q

pros and cons of fossil fuel power plants and natural gas power plants

A

Fossil fuel power plants

  • reasonably efficient: 35%
  • contribute greenhouse gases to atmosphere

Natural as power plants

  • more efficient: 60%
  • smaller greenhouse gas emissions
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14
Q

Advantages of fossil fuels

A
  • relatively cheap while they last
  • high power output (high energy density)
  • variety of engines and devices use them directly and easily
  • extensive distribution network is in place
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15
Q

fossil fuel disadvantages

A
  • will run out
  • pollute the environment
  • contribute to greenhouse effect by releasing greenhouse gases into atmosphere
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16
Q

nuclear reactor

A

machine in which nuclear fission reactions take place producing energy

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17
Q

What are the two types of fission reactor?

A
  • pressurised water reaction (PWR)
  • gas cooled reactor
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18
Q

pressurised water reactor

A
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19
Q

gas cooled reactor

A
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20
Q

What is the fuel of a nuclear reactor?

A

uranium-235

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21
Q

chain reaction

A

self-sustaining reaction

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22
Q

What is required for the chain reaction to get going?

A
  • critical mass of uranium-235 must be present
  • otherwise neutrons escape without causing further reactions
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23
Q

Describe fission

A
  • neutrons produced can be used to collide with other nuclei in reactor
  • produces more fission, energy and neutrons
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24
Q

moderator

A
  • uranium-235 cannot capture neutrons at speed from fission
  • slowing of neutrons through collisions with moderator
  • material surrounding fuel rods
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25
Q

fuel rods

A

tubes containing uranium

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26
Q

What materials is the moderator usually?

A

graphite or water

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27
Q

heat exchanger

A
  • when neutrons collide with moderator, transfer energy to moderator
  • extracts heat from moderator
  • uses cold water that circulates in pipes throughout the moderator
  • water turned into steam at high temperature and pressure
  • steam is used to turn turbines producing energy
28
Q

control rods

A
  • absorb neutrons when too many neutrons are present so decrease rate of reaction
  • if rate of reaction needs to be increased, remove control rods
29
Q

advantages of nuclear power

A
  • high power output
  • large reserves of nuclear fuels
  • does not produce greenhouse gases
30
Q

disadvantages of nuclear power

A
  • radioactive waste products difficult to dispose of
  • major public health hazard if something goes wrong
  • problems associated with uranium mining
  • possibility of producing materials for nuclear weapons
31
Q

advantages of solar power

A
  • free
  • inexhaustible
  • clean
32
Q

disadvantages of solar power

A
  • works during day only
  • affected by cloudy weather
  • low power output
  • requires large areas
  • initial costs high
33
Q

solar panels

A
  • sunlight used to heat water for heating house
  • blackened surface below glass collects sunlight, glass protects but coated to reduce reflection
  • tend to be bulky and cover too much space
34
Q

photovoltaic cells

A
  • converts sunlight directly into direct current
  • 30% efficiency
  • sunlight releases electrons and creates potential difference across cell
35
Q

advantages of hydroelectric power

A
  • ‘free’
  • inexhaustible
  • clean
36
Q

disadvantages of hydroelectric power

A
  • very dependent on location
  • requires drastic changes to environment
  • initial costs high
37
Q

pumped storage system

A

water that flows to lower heights is pumped back to its original height using generators of plant as motors

38
Q

advantages of wind power

A
  • ‘free’
  • inexhaustible
  • clean
39
Q

disadvantages of wind power

A
  • dependent on local wind conditions
  • aesthetic problems
  • noise problems
40
Q

energy balance

A

energy input to earth must be equal to energy output because temperature constant

41
Q

What are the drawbacks of energy balance model?

A
  • zero-dimensional model
  • interactions between surface and atmosphere ignored - e.g. latent heat flows
42
Q

enhanced greenhouse effect

A

additional warming due to increased quantities of greenhouse gases in atmosphere due to human activity

43
Q

absolute meaning

A

Kelvin

44
Q

how do bodies radiate energy?

A
  • energy radiated through electromagnetic waves
  • created by oscillating electric charges in atoms of body
45
Q

emissivity

A
  • ratio of power radiated per unit area by an object to the power radiated per unit area by a black body
  • between 0 and 1
46
Q

black body

A
  • perfect radiator and absorber
  • e = 1
  • e.g. charcoal (black and dull surface)
47
Q

Wein’s law graph: increase temperature

A
  • peak of curve occurs at lower wavelengths
  • height of peak increases
48
Q

Weins law graph: same temperature, different emissivities

A
  • height of curve decreases as emissivity decreases
  • otherwise identical
49
Q

intensity

A

power of radiation received per unit area

50
Q

area of a sphere

A

4*pi*d2

51
Q

albedo

A

ratio of power of radiation scattered from the body to the total power incident on the body

52
Q

high albedo example

A

snow

53
Q

low albedo example

A

charcoal

54
Q

what factors vary the albedo of the earth?

A
  • time of year (many clouds = increase albedo)
  • latitude (more snow = increase albedo)
  • desert land (high albedo)
  • forest (low albedo)
  • water (low albedo)
55
Q

show solar constant

A
56
Q

show average incident intensity

A
57
Q

energy flow diagram of greenhouse effect

A
58
Q

greenhouse effect

A

warming of the Earth caused by infrared radiation emitted by the Earth’s surface which is absorbed by various gases in the Earth’s atmosphere and then partly re-radiated towards the surface

59
Q

greenhouse gases

A
  • water vapor
  • carbon dioxide
  • methane
  • nitrous oxide
60
Q

natural sources of greenhouse gases

  1. water vapor
  2. carbon dioxide
  3. methane
  4. nitrous oxide
A
  1. evaporation of water from oceans, rivers and lakes
  2. forest fires, volcanic eruptions, evaporation of ocean water
  3. wetlands, oceans, lakes and rivers, termites
  4. forests, oceans, soil and grasslands
61
Q

anthropogenic sources of greenhouse gases

  1. water vapor
  2. carbon dioxide
  3. methane
  4. nitrous oxide
A
  1. irrigation
  2. burning fossil fuels in power plants and cars, burning forests
  3. flooded rice fields, farm animals, processing of coal, natural gas and oil, burning biomass
  4. burning fossil fuels, manufacturing cement, fertilisers, deforestation
62
Q

Why do greenhouse gases absorb infrared radiation?

A

resonance

63
Q

explain resonance

A
  • the natural frequency of oscillation of the bonds within molecules of the gas is in infrared region
  • if driving frequency from radiation emitted from the Earth is equal to natural frequency of molecule resonance occurs
  • amplitude of molecular vibration increases, temperature increases
64
Q

enhanced greenhouse effect

A

greenhouse effect caused by human activities

65
Q

what are the three possible explanations for global warming?

A
  1. changes in composition of greenhouse gases in atmosphere
  2. change in intensity of radiation emitted by the sun linked to increased solar flare activity
  3. cyclical changes in the earth’s orbit and volcanic activity
66
Q

what happens to the albedo of the earth as temperature rises?

A
  • albedo decreases
  • snow and ice melts, increasing area of oceans which have lower albedo than snow

IB Physics (14 decks)

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