Engineering
Basic

Efficiency

Ratio of useful output to input power.

Formula

η=PoutPin×100%\eta = \frac{P_{out}}{P_{in}} \times 100\%

Variables

P_{out}Output
P_{in}Input

Example

A motor giving 800 W out for 1000 W in is 80% efficient.

Did You Know?

No real machine is 100% efficient — the second law of thermodynamics forbids it.

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