Last Updated Sep 26, 2025

Efficiency Simplified Revision Notes for GCSE AQA Physics Combined Science

Revision notes with simplified explanations to understand Efficiency quickly and effectively.

Learn about Energy Changes in a System for your GCSE Physics Combined Science Exam. This Revision Note includes a summary of Energy Changes in a System for easy recall in your Physics Combined Science exam

310+ students studying

Energy Changes in a System Quizzes

Test your knowledge with quizzes.

Energy Changes in a System Flashcards

Practice with bite-sized questions.

Energy Changes in a System Questions by Topic

Prepare with real exam question.

Print Free PDF

1.1.14 Efficiency

Efficiency

infoNote

Efficiency is the ratio of the useful work done by a machine, engine, device, etc, to the energy supplied to it, often expressed as a percentage.

infoNote

Formula:

$$efficiency =\frac{useful\ energy\ output}{total\ energy\ input} = \frac{useful\ power\ output}{total\ power\ input}$$

• The efficiency of a system can be increased by: o Reducing waste output (lubrication, thermal insulation, etc.) o Recycling waste output (e.g. absorbing thermal waste and recycling as input energy)

lightbulbExample

Example Question: A light bulb uses 100 joules of electrical energy but only gives off 20 joules of light energy. How efficient is the light bulb?

Solution:

1. What do we know?

• The light bulb uses 100 joules of energy.
• It only gives off 20 joules of light energy.

infoNote

2. Use the efficiency formula:

$$Efficiency = \frac{Useful energy output}{Total energy input}x100$$$$Efficiency = \frac{20J}{100J} X 100$$

2. Do the maths:

$$Efficiency=0.2×100=20$$

Answer:

infoNote

The light bulb is 20% efficient.

Only available for registered users.

Sign up now to view the full note, or log in if you already have an account!

Sign up with GoogleSign up with Apple

500K+ Students Use These Powerful Tools to Master Efficiency For their GCSE Exams.

Enhance your understanding with flashcards, quizzes, and exams—designed to help you grasp key concepts, reinforce learning, and master any topic with confidence!

Other Revision Notes related to Efficiency you should explore

Discover More Revision Notes Related to Efficiency to Deepen Your Understanding and Improve Your Mastery

96%

114 rated

Energy Changes in a System

Energy Stores & Transfers

465+ studying

182KViews

View Note

96%

114 rated

Energy Changes in a System

Energy Transfer & Work Done

435+ studying

185KViews

View Note

96%

114 rated

Energy Changes in a System

Kinetic Energy

359+ studying

187KViews

View Note

96%

114 rated

Energy Changes in a System

Gravitational Potential Energy

434+ studying

192KViews

View Note