Topic 8 applies physics to energy production and climate science. Students compare energy sources, analyse efficiency, understand the greenhouse effect, and evaluate the physics behind climate change.
Primary sources: fossil fuels (coal, oil, gas), nuclear, solar, wind, hydroelectric, geothermal, tidal, biomass. Specific energy (J/kg) and energy density (J/m³). Sankey diagrams show energy flow and losses. Efficiency = useful output / total input × 100%. Most thermal plants: ~30-40% efficient. Combined cycle gas: ~60%.
Conduction: energy transfer through particle collisions (metals are good conductors). Convection: energy transfer through fluid movement (warm fluid rises). Radiation: energy transfer through electromagnetic waves (infrared). Black bodies: perfect absorbers/emitters. Stefan-Boltzmann law: P = σAT⁴. Wien\'s displacement law: λ_max·T = 2.9 × 10⁻³ m·K.
Earth absorbs solar radiation (short wavelength) and re-emits infrared (long wavelength). Greenhouse gases (CO₂, CH₄, H₂O, N₂O) absorb and re-emit infrared, warming the surface. Enhanced greenhouse effect: human activities increase GHG concentrations → additional warming. Evidence: ice cores, temperature records, CO₂ measurements (Keeling curve).
Solar: P = solar constant × area × efficiency × cosθ. Wind: P = ½ρAv³ (depends on cube of wind speed). Hydroelectric: P = ρgQh. Nuclear: high energy density, low carbon, but radioactive waste. Fossil fuels: high energy density, reliable, but CO₂ emissions. Each source has trade-offs in reliability, environmental impact, cost, and scalability.
Nuclear power is not classified as renewable because it uses uranium, a finite resource. However, it is classified as low-carbon because it produces minimal CO₂ during operation (comparable to wind/solar over the full lifecycle). The main environmental concerns are radioactive waste disposal, catastrophic accident risk (though statistically rare), and uranium mining impact. Some consider thorium reactors and future fusion reactors as more sustainable nuclear options.
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