Sources of Energy
What is tested
This domain tests renewable and non-renewable sources, fossil fuels, solar energy, wind, hydro, biomass, biogas, geothermal, tidal, wave, nuclear energy and environmental consequences. Questions often compare sources or ask for advantages and limitations.
Core rules
- Non-renewable sources such as coal, petroleum and natural gas are finite and release pollutants and CO2. Renewable sources are replenished naturally.
- Solar devices include solar cookers, solar cells and solar water heaters. Solar cells convert light directly into electricity.
- Wind energy needs consistent wind; windmills convert kinetic energy of wind into electricity.
- Hydroelectric power uses potential energy of stored water. Dams affect ecosystems and displace people.
- Biogas is mainly methane, produced by anaerobic decomposition of biomass. Nuclear fission releases large energy but produces radioactive waste.
- The Sun's energy comes from nuclear fusion, not fission.
Worked example
A house uses five 100 W solar panels for 6 hours a day. Energy = 5 × 100 W × 6 h = 3000 Wh = 3 kWh per day. If electricity costs a given rate per kWh, multiply 3 by that rate. This shows why units must be converted from Wh to kWh.
Traps
Nuclear fusion powers the Sun; nuclear reactors use fission. Biogas is not mainly CO2. Fossil fuels are non-renewable even if reserves seem large. Wind and solar are intermittent, so storage or backup is needed.