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Efficiency - GCSE Physics Definition

Reviewed by: Ann Howell

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What is Efficiency?

In GCSE Physics, the efficiency of a system is a measure of the amount of useful and wasted energy in an energy transfer. It is defined as either the ratio of useful energy output to total energy input or the ratio of useful power output to total power input. A system with a high efficiency is one in which most of the energy transferred is useful. 

Efficiency is a ratio so has no units and can be expressed as a decimal or a percentage. Efficiency is calculated using one of the following relevant equations:

efficiency space equals space fraction numerator useful space output space energy space transfer over denominator total space input space energy space transfer end fraction

efficiency space equals space fraction numerator useful space power space output over denominator total space power space input end fraction

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Ann Howell

Reviewer: Ann Howell

Expertise: Physics Content Creator

Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

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