This how it works covers Why Is Efficiency Never 100%? 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 4 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 13
Practice
19 questions
Recall
4 flashcards
⚙️ Why Is Efficiency Never 100%?
The second law of thermodynamics tells us that energy tends to spread out and become less useful. In every real energy transfer, some energy is dissipated into the thermal energy store of the surroundings — this is energy that cannot easily be recovered and used again.
Sources of energy waste include:
- Friction — moving parts rub against each other, producing heat (e.g., engine pistons, brake pads)
- Electrical resistance — current flowing through wires heats the wire (P = I²R losses in transmission lines)
- Sound — vibrations that carry energy away (e.g., noisy machinery)
- Light emission — incandescent bulbs emit heat and infrared, not just visible light
- Fluid drag — air resistance or water resistance converts kinetic energy to heat
Engineers reduce these losses through lubrication (reducing friction), better insulation (reducing heat loss), streamlining (reducing drag), and using superconducting materials (reducing resistance).
Keep building this topic
Read this section alongside the surrounding pages in Efficiency. That gives you the full topic sequence instead of a single isolated revision point.
Practice Questions for Efficiency
Which equation correctly defines efficiency?
Explain one method that can be used to reduce unwanted energy transfers in a machine and state how it reduces waste.
Quick Recall Flashcards
19 questions on Efficiency — practise free
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