This topic summary covers Topic Summary: Efficiency within Efficiency for GCSE Physics. Revise Efficiency in Energy for GCSE Physics with 19 exam-style questions and 4 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 13 of 13
Practice
19 questions
Recall
4 flashcards
Topic Summary: Efficiency
Key Equations
- Efficiency = Useful output ÷ Total input
- Efficiency (%) = (Useful ÷ Total) × 100
- Wasted = Total input − Useful output
- Same formula works with power (W)
Key Terms
- Efficiency — ratio of useful output to total input (no unit)
- Useful output — energy in intended form
- Wasted energy — unintended outputs (mainly heat)
- Sankey diagram — width = energy amount
- Dissipated — spread into surroundings as heat
Key Rules
- Efficiency is always less than 100%
- Energy is conserved (never lost)
- Wasted energy goes to thermal store
- Efficiency has NO unit
Improving Efficiency
- Lubrication — reduces friction
- Insulation — reduces heat loss
- Streamlining — reduces air resistance
- Superconductors — reduce electrical resistance