Energy Efficiency and Resources
Efficiency measures how much useful energy you get out compared to what you put in - and it's never 100% because some energy always gets "wasted" as heat or sound. You can improve efficiency through insulation, lubrication, or streamlining, which reduces energy losses.
Renewable energy sources like biofuels, wind, and solar power won't run out and generally cause less environmental damage. Biofuels are particularly interesting because they're carbon neutral - they only release the COโ that plants absorbed while growing.
Non-renewable sources like coal, oil, and gas will eventually run out and contribute to global warming through greenhouse gas emissions. However, they're currently more reliable and cheaper than most renewable alternatives.
Exam Tip: Learn the advantages and disadvantages of each energy source - comparison questions are extremely common and easy marks if you've memorised the key points for wind, solar, geothermal, hydro-electric, wave, and tidal power.