Efficiency is the useful energy output divided by the corresponding total energy input.
Difficulty
Intermediate
Read time
5 min
Prerequisites
Basic algebra, consistent units, and the stated model assumptions
Source
OpenStax, College Physics 2e, §7.6 (Paul Peter Urone and Roger Hinrichs)OpenFormulaGraph equation reference; FormuLab adaptation details and license are provided below.
Adapted from OpenFormulaGraph, under CC BY 4.0.
FormuLab adapted wording, notation, applicability conditions and topic placement, and expanded the numerical check into a worked example. The textbook section reference was corrected.
Efficiency is the useful energy output divided by the corresponding total energy input. The comparison must use the same process boundary and time interval; the rest of the energy remains in other forms.
| Symbol | Meaning | Units |
|---|---|---|
| Efficiency | ||
| Work (output) | ||
| Work (input) |
Compare useful output with total input.
Compare efficiencies for a consistent system boundary.
A process supplies 30 J of useful work from 100 J of input energy. Find its efficiency as a fraction.
OpenFormulaGraph equation reference; FormuLab adaptation details and license are provided below.
Adapted from OpenFormulaGraph, under CC BY 4.0.
FormuLab adapted wording, notation, applicability conditions and topic placement, and expanded the numerical check into a worked example. The textbook section reference was corrected.
Assumptions
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