Effects of Current and Natural Resources
What this domain tests
This domain links the heating, magnetic and chemical effects of current to the way we source energy and manage ecosystems, waste and natural resources.
Core rules
- Renewable sources include solar, wind, hydro, tidal, geothermal and biomass; non-renewable sources include coal, petroleum, natural gas and nuclear fuel. Fossil fuels are finite and add CO₂.
- A solar cell converts light directly into electricity; a solar cooker uses reflecting surfaces; biogas is roughly 75% methane from anaerobic decomposition of organic waste.
- Nuclear fission splits heavy nuclei and releases energy; fusion powers the Sun. Chemical effects of current appear in electrolysis and electroplating.
- Food chains run producers → consumers → decomposers, rarely beyond four or five trophic levels because about 90% of energy is lost at each transfer (10% law).
- Stratospheric ozone absorbs ultraviolet radiation, and CFCs deplete it. Greenhouse gases such as CO₂ and CH₄ trap infrared radiation and warm the surface.
- Sustainable management includes the 3Rs, rainwater harvesting, watershed development, check dams, contour ploughing, afforestation and controlled use of forests and wildlife.
Worked example
Producers in a food chain hold 10,000 J. By the 10% law, herbivores receive 1,000 J, secondary consumers 100 J and tertiary consumers 10 J. Reasoning: usable energy falls tenfold at each step, so top predators are few and need large territories.
Traps
- Do not merge the ozone problem (UV shield, CFCs) with the greenhouse effect (heat trapping, CO₂).
- The 10% law moves energy up the chain; energy is lost as heat and is not recycled.
- Biogas is mainly methane, not mainly carbon dioxide.
- Renewable does not mean inexhaustible: groundwater and fertile soil can still be depleted.