Mr. Rogers' IB Physics Topics
|Syllabus||1st Quarter||2nd Quarter||3rd Quarter||4th Quarter||IB Objectives|
|Core Thermo||HL Thermo||Core Energy||Core Waves||HL Waves||HL Digital Tech|
|Opt SL/HL EM Waves||Opt SL/HL Com||Core Nuclear||HL Nuclear||Opt HL Relativity||Opt HL Medical|
IB Physics Standards: Items directly related to the standards are shown in blue
Topic 8: Energy, power and climate change
|Essential Question: Assuming no friction, is it possible to convert heat into mechanical energy with 100% efficiency?|
Energy degradation and power generation
State that thermal energy may be completely converted to work in a single process, but that continuous conversion of this energy into work requires a cyclical process and the transfer of some energy from the system. Place a leak-proof friction free piston at the center of a perfectly insulated infinitely long cylinder, so that there is gas trapped behind the piston. Continuously heat the trapped gas so that it maintains a constantly elevated pressure that pushes the piston forward; 100% of the heat energy could be converted into work. However, in the real world, at some point the piston reaches the end of the cylinder. The high pressure gas has to be released from the cylinder--essentially dumping the energy contained in it--and work then has to be done to return the piston to its original position so that the cycle can be repeated. With a continuous cycle, 100% of the heat energy can NEVER be converted to work.
Explain what is meant by degraded energy. When thermal energy is converted to mechanical or electrical energy, part of the thermal energy has to be expelled into the environment. This energy is considered degraded. Degraded energy still exists but essentially can no longer be converted into mechanical or electrical energy. In other words, degraded energy can no longer do work.
Of course, the degraded energy could, in theory, be sent through another heat engine and then its degraded energy sent through yet another an infinitum, but each time the degraded energy is expelled it has to be expelled to a lower temperature. To convert 100% of the thermal energy into mechanical energy would require that the last heat engine in the series would have to expel its energy at a temperature of absolute zero--an impossibility.
Heat engine: Heat engines are devices used to continuously convert thermal energy into mechanical energy. Steam engines, gas turbines, internal combustion engines in cars, and diesel engines are all heat engines. If thermal energy could be continuously transferred into a gas making it expand and push a piston in an infinitely-long friction-free cylinder, 100% of the thermal energy could theoretically be converted into mechanical energy. In the real world however all heat engines must go through a thermodynamic cycle that results in part of the input heat being expelled to the environment.
Carnot efficient: is the maximum theoretical efficiency a friction-free heat engine could have. It's always less than 100% and for real heat engines may be less than 80%. Add friction and other losses and the actual efficiency is typically less than 50%.
|Essential Question: How does the world power itself?|
Construct and analyze energy flow diagrams (Sankey diagrams) and identify where the energy is degraded.
Outline the principal mechanisms involved in the production of electrical power.
source of heat: usually coal or nuclear but could be solar or geothermal
heat engine: converts thermal energy to mechanical energy (work)
alternator: converts mechanical energy to electrical energy.
transmission/distribution system: sends electrical energy to end users
|Essential Question: How does the world power itself?|
World energy sources
Identify different world energy sources and the relative proportions of different energy sources that are available.
|Essential Question: Why is electrical energy so useful?|
Explain why, for humanity, electrical energy is the most useful form, followed by mechanical. Explain why electrical energy is also the most expensive in terms of the total energy and equipment required to produce it.
The ability to do useful work and or carry information increases as a quantity of energy moves higher on the energy pyramid. For thermal energy, a higher level on the pyramid represents a higher temperature and, hence, a higher possible Carnot efficiency for conversion to the mechanical energy.
When attempting to convert a quantity of energy to a form that's higher on the energy usefulness pyramid, invariably a large amount will be degraded. This degraded energy still exists but is in thermal form at such a low level on the pyramid that it essentially can never move to a higher level. Going down the pyramid is another matter: 90% or more of electrical energy can be converted directly to mechanical form and 100% to thermal, 100% of mechanical energy can be converted to thermal form, and 100% of high level (thermal energy at a high temperature) can be converted to low level thermal energy (thermal energy at a low temperature).
Outline and distinguish between renewable and non-renewable energy sources.
|Source||Original Source||Available Supply||Type Available|
|wind turbine||present-day Sun||lifetime of Sun||mechanical||Conceivably, the entire Earth's surface can act as a solar collector with energy harvested by wind turbines.|
|present-day Sun||lifetime of Sun||electrical||Available power limited by the area of the collector system that's ultimately limited by available land area.|
solar heating panel
|present-day Sun||lifetime of Sun||thermal||Available power limited by the area of the collector system that's ultimately limited by available land area.|
|hydro||present-day Sun||lifetime of Sun||mechanical||Energy is stored in the water as gravitational potential energy, hence the height of the dam is a major factor and helps limit the number of potential hydro sites|
|geothermal (volcanic activity)||volcanic activity||Thousands of years +||thermal||Few usable sites are available|
|tidal||orbital motions of Earth and Moon||millions of years||mechanical||In most areas the change in height of the water level with changing tide is so small that it would require a huge area to gain any useful energy|
|fossil fuels||ancient Sun||hundreds of years||thermal|
|fission (uranium)||formation of Solar Syst.||hundreds of years||thermal|
|fusion (hydrogen)||formation of Universe||millions of years||thermal|
|Essential Question: Why is energy density such an important issue?|
Define the energy density of a fuel.
* These are forms of energy storage. Whether they are renewable or not depends on whether the energy stored in them came from a renewable source.
Discuss how choice of fuel is influenced by its energy density.
For transportation applications energy density is a major consideration. It determines the following for a vehicle:
size - energy density by volume is key here.
mass - the higher the energy density the lower the mass when the fuel supply is fully loaded.
acceleration - While energy density is not the only consideration, anything that increases mass tends to decrease acceleration.
range - the higher the energy density, the greater the range or number of miles driven for a given fuel capacity.
fuel efficiency - While energy density is not the only consideration or even the main consideration, anything that increases mass will have less fuel efficiency (miles traveled per unit of fuel) because it will take more energy to accelerate the vehicle
Discuss the relative advantages and disadvantages of various energy sources.
Fossil fuel power production
Outline the historical and geographical reasons for the widespread use of fossil fuels.
Discuss the energy density of fossil fuels with respect to the demands of power stations.
Discuss the relative advantages and disadvantages associated with the transportation and storage of fossil fuels.
|Fossil Fuel||Storage||Distribution to customer||Transport from well/mine to distribution network|
|natural gas||pressurized tanks: These have thick walls and are relatively expensive to build. To get a higher density (thus reducing tank size) natural gas is often liquefied. This requires cryogenic temperatures and specialized materials.||
|propane||pressurized tanks: These have thick walls and are relatively expensive to build.||
|butane||pressurized tanks: These have thick walls and are relatively expensive to build.||
|gasoline||atmospheric pressure tanks: These have relatively thin walls and are relatively inexpensive to build.||
|diesel / fuel oil||atmospheric pressure tanks: These have relatively thin walls and are relatively inexpensive to build.||
|coal||piles: requires no tank, just some land area essentially no expense to build||
State the overall efficiency of power stations fuelled by different fossil fuels.
Describe the environmental problems associated with the recovery of fossil fuels and use such as electricity generation, transportation, and heating.
|Type||Definition / Significance||Origen|
|CO2||A major exhaust component from burning fossil fuels is also a greenhouse gas that contributes significantly to global warming.||use|
|Ground level ozone||Ozone in the upper atmosphere helps reduce the amount of harmful UV reaching Earth from the sun. However, at ground level ozone is a major health hazard.||use|
|NOx (pronounced knocks)||When burning a fossil fuel using air, a small
amount nitrogen will combine with oxygen forming various nitrogen oxides.
Low level ozone is formed when NOx and VOCs react in the presents of
ultraviolet light (from sunlight). Low level ozone is a major lung irritant.
Note that NOx is also naturally formed by lightning. Here, however, the NOx generally dissolves in rain water and acts as a type of nitrogen fertilizer.
|Particulates||Dust or smoke particles in the air. Particulates reduce visibility and are a lung irritant.||use|
|SOx (pronounced socks)||Various sulfur oxides are formed when sulfur containing fossil fuels are burned. SOx comes primarily from high sulfur coal burning and is a major cause of acid rain.||use|
|VOC||VOCs or volatile organic compounds refer to fossil fuel components that evaporate or escape into the air. VOCs react with NOx in the presents of sun light producing smog and ground level ozone a major lung irritant. VOCs themselves can create significant health problems. For example, benzene is a major carcinogen (cancer causing compound), is volatile, and present at about 9% in gasoline. Some types of VOCs such as methane can act as powerful greenhouse gasses.||recovery and use|
A fog-like combination of all forms of visible air pollution.
Ground and Surface Water / Soil Contamination
|Heavy Metals||recovery and use|
|Organic compounds||recovery and use|
|Destruction of Habitat and Land Use Issues|
|Solid waste||Ash from coal burning can be radioactive (low level) and contain heavy metals. It often ends up in land fills.||recovery and use|
Non-fossil fuel power production
Describe how neutrons produced in a fission reaction may be used to initiate further fission reactions (chain reaction).
low-energy neutrons (≈ 1 eV) favor nuclear fission.
Describe what is meant by fuel enrichment.
Describe the main energy transformations that take place in a nuclear power station.
Discuss the role of the moderator and the control rods in the production of controlled fission in a thermal fission reactor.
Discuss the role of the heat exchanger in a fission reactor.
Describe how neutron capture by a nucleus of uranium 238 (238U) results in the production of a nucleus of plutonium 239 (239Pu).
Describe the importance of plutonium 239 (239Pu) as a nuclear fuel.
Discuss safety issues and risks associated with the production of nuclear power.
the possibility of thermal meltdown and how it
problems associated with nuclear waste
problems associated with the mining of uranium
the possibility that a nuclear power program
Outline the problems associated with producing nuclear power using nuclear fusion.
Distinguish between a photovoltaic cell and a solar heating panel.
Outline reasons for seasonal and regional variations in the solar power incident per unit area of the Earth’s surface.
Solve problems involving specific applications of photovoltaic cells and solar heating panels.
Distinguish between different hydroelectric schemes.
• water storage in lakes
• tidal water storage
• pump storage.
Describe the main energy transformations that take place in hydroelectric schemes.
Solve problems involving hydroelectric schemes.
Outline the basic features of a wind generator.
Determine the power that may be delivered by a wind generator, assuming that the wind kinetic energy is completely converted into mechanical kinetic energy, and explain why this is impossible.
Describe the principle of operation of an oscillating water column (OWC) ocean-wave energy converter.
Determine the power per unit length of a wavefront, assuming a rectangular profile for the wave.
|Essential Question: Is global warming/climate disruption avoidable?|
Calculate the intensity of the Sun’s radiation incident on a planet.
Students should know that the Earth’s albedo
Oceans have a low value
snow a high value.
global annual mean albedo is 0.3 (30%) on Earth.
The greenhouse effect
Identify the main greenhouse gases and their sources.
The gases to be considered are CH4, H2O, CO2 and
N2O. It is sufficient for students to know that each
- has natural and man-made origins.
Explain the molecular mechanisms by which greenhouse gases absorb infrared radiation.
Students should be aware of the role played by
resonance. The natural frequency of oscillation
of the molecules of greenhouse gases is in the
Analyse absorption graphs to compare the relative effects of different greenhouse gases.
Outline the nature of black-body radiation.
Draw and annotate a graph of the emission spectra of black bodies at different temperatures.
State the Stefan–Boltzmann law and apply it to compare emission rates from different surfaces.
Apply the concept of emissivity to compare the emission rates from the different surfaces.
Surface heat capacity is the energy required to raise
the temperature of unit area of a planet’s surface by
- one degree, and is measured in J m–2 K–1.
Solve problems on the greenhouse effect and the heating of planets using a simple energy balance climate model.
A planet’s temperature over a period of time is given
(incoming radiation intensity –outgoing radiation
intensity) × time / surface heat capacity.
Students should be aware of limitations of the
model and suggest how it may be improved.
Aim 7:A spreadsheet should be used to show a
simple climate model. Computer simulations could
be used to show more complex models (see OCC
Describe some possible models of global warming.
Students must be aware that a range of models
has been suggested to explain global warming,
including changes in the composition of
greenhouse gases in the atmosphere, increased
solar flare activity, cyclical changes in the Earth’s
orbit and volcanic activity.
State what is meant by the enhanced greenhouse effect. -- caused by human activity
Identify the increased combustion of fossil fuels as the likely major cause of the enhanced greenhouse effect.
Describe the evidence that links global warming to increased levels of greenhouse gases.
For example, international ice core research
produces evidence of atmospheric composition
and mean global temperatures over thousands
of years (ice cores up to 420,000 years have been
drilled in the Russian Antarctic base, Vostok).
State that one possible effect of the enhanced greenhouse effect is a rise in mean sea-level.
Outline possible reasons for a predicted rise in mean sea-level.
are difficult to make due to factors such as:
Students should be aware that precise predictions
• anomalous expansion of water
• different effects of ice melting on sea wate compared to ice melting on land.
Identify climate change as an outcome of the enhanced greenhouse effect.
Solve problems related to the enhanced greenhouse effect.
Problems could involve volume expansion, specific
- heat capacity and latent heat.
Identify some possible solutions to reduce the enhanced greenhouse effect.
Students should be aware of the following:
• greater efficiency of power production
• replacing the use of coal and oil with natural gas
• use of combined heating and power systems
• increased use of renewable energy sources and
• carbon dioxide capture and storage
• use of hybrid vehicles.
Discuss international efforts to reduce the enhanced greenhouse effect.
These should include, for example:
• Intergovernmental Panel on Climate Change
• Kyoto Protocol
• Asia-Pacific Partnership on Clean Developmentand Climate (APPCDC).