This definitions covers Key Definitions 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 6 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 6 of 13
Practice
19 questions
Recall
4 flashcards
📖 Key Definitions
- Efficiency
- The ratio of useful output energy to total input energy. Can be expressed as a decimal (0 to 1) or percentage (0% to 100%). Always less than 1 (or 100%) in real devices.
- Useful energy output
- The energy transferred in the desired, intended form (e.g., kinetic energy from a motor, light from a bulb).
- Wasted energy
- Energy transferred in an unintended, unwanted form — most commonly as thermal energy (heat) due to friction or resistance. Wasted energy = total input − useful output.
- Sankey diagram
- A flow diagram where arrow widths are proportional to the energy they represent. Used to visualise energy transfers and identify wasted energy.
- Dissipated energy
- Energy that has been spread out into the thermal energy store of the surroundings, making it difficult to recover and use again.