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IB Physics Vocab
Section: Energy, Power and Climate Change
| Term | Definition |
|---|---|
| Second Law of Thermodynamics | 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. |
| Degraded Energy | In any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to perform useful work. |
| Sankey Diagram | energy flow diagram |
| Renewable Energy Source | source of energy that cannot be used up (eg. –hydroelectric, photovoltaic cells, active solar heaters, wind, biofuels) (NOTE: In most instances, the Sun is the primary energy source for world energy.) |
| Non-renewable Energy Source | source of energy that can be used up (eg. – coal, oil, natural gas, nuclear) |
| Energy Density (of a fuel) | the ratio of the energy released from the fuel to the mass of the fuel consumed |
| Fossil Fuels | coal, oil, and natural gas (NOTE: Industrialization led to a high rate of energy usage leading to industry being developed near large deposits of fossil fuels.) |
| Chain Reaction | neutrons released from one fission reaction go on to initiate further reactions (NOTE: Only low-energy neutrons (≈ 1 eV) favor nuclear fission.) |
| Critical Mass | minimum mass of radioactive fuel block needed for a chain reaction to occur |
| Controlled Nuclear Fission | used for power production |
| Uncontrolled Nuclear Fission | used for nuclear weapons |
| Fuel Enrichment | process by which the percentage composition of a desirable radioactive nuclide (eg. – uranium-235) is increased in order to make nuclear fission more likely |
| Moderator | Most neutrons released in fission are fast neutrons, so a moderator is used to reduce their energy down to thermal levels to ensure that the fission is self-sustaining. (eg. – may be made of solid graphite or steam) |
| Control Rods | are used to remove any excess neutrons to ensure the fission reaction continues safely (eg. – may be made of cadmium or boron steel) |
| Heat Exchanger | This allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. Reactions increase temperature in the core and this thermal energy is transferred to water and the steam that is produced turns the turbines. |
| Photovoltaic Cell (solar cell photocell) | converts a portion of the solar radiation into a potential difference (voltage) using a semiconductor (A typical photovoltaic cell produces a very small voltage, so it's usually used to run electrical devices that do not require a great deal of energy.) |
| Active Solar Heater (solar panel) | designed to capture as much thermal energy as possible by allowing solar radiation to heat water running through a pipe in the panel. |
| Oscillating Water Column (OWC) Ocean-Wave Energy Converter | device built on land that uses the kinetic energy of waves to force air in and out of a turbine which generates electrical energy |
| Albedo (α) | fraction of the total incoming solar radiation received by a planet that is reflected back out into space (NOTE: global annual mean albedo is 0.3 for Earth) |
| Greenhouse Effect | Short wavelength radiation received from the Sun causes the Earth’s surface to warm up.Earth will then emit longer wavelength radiation (infra-red) which is absorbed by some gases (eg. - water vapor) in the atmosphere and re-radiated in all directions. |
| Global Warming | increase in mean temperature of the Earth in recent years |
| Enhanced (Anthropogenic) Greenhouse Effect | Human activities, mainly related to the burning of fossil fuels, have released extra carbon dioxide into the atmosphere, thereby enhancing or amplifying the greenhouse effect (a possible cause of global warming). |
| Black-Body Radiation | radiation emitted by a “perfect” emitter of radiation |
| Stefan-Boltzmann Law | The total power radiated by a black-body per unit area is proportional to the fourth power of the temperature of the body. (power = σAT4) |
| Emissivity (ε) | ratio of power emitted by an object to the power emitted by a black-body at the same temperature. |
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