Energy Transferred by Working
Electricity and Magnetism

Calculating energy efficiencies

Physics Narrative for 14-16 Supporting Physics Teaching

How to find efficiencies

Efficiency is simply a measure of success – it tells you how much energy is squandered and how much ends up in the store that you designed the system for. Often, but not always, the squandered energy will be shifted to many stores – dissipation has occurred.

Calculate the percentage of the input energy ending up in the desired output and you have the efficiency: efficiency = energyoutenergyin × 100 %.

A support sheet showing how to calculate efficiency (see below).


Download the support sheet / student worksheet for this activity.

Energy Transferred by Working
appears in the relation dU=dQ+dW
is used in analyses relating to Working Engines Thermionic Emission
is a special case of Work
has the special case Potential Energy Kinetic Energy
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