GCSE Physics · Edexcel 1PH0 · Topic 3B
Efficiency and reducing energy waste
Key points
- Efficiency = , given as a decimal or a percentage. It can never be more than 100%.
- Wasted energy is usually dissipated to the surroundings as thermal energy, making it spread out and less useful.
- Lubrication reduces friction in moving parts, so less energy is wasted by heating.
- Thermal insulation (loft insulation, cavity walls, double glazing) reduces energy transfer from homes.
- Thicker walls and materials with lower thermal conductivity reduce the rate of energy transfer by heating.
- In exam answers, say where the wasted energy goes and how a change reduces it, e.g. 'less friction, so less energy dissipated as thermal energy'.
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No real device turns all of its input energy into what we want. This sub-topic is about measuring how good a device is at its job and the practical ways to waste less energy, from oiling machines to insulating houses.
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