Efficiency of a System
- The efficiency of a system is the ratio of the useful energy output from the system to the total energy input
- If a system has high efficiency, this means most of the energy transferred is useful
- If a system has low efficiency, this means most of the energy transferred is wasted
- Multiplying this ratio by 100 gives the efficiency as a percentage
- The efficiency is calculated using the equation:
Efficiency equation in terms of energy
- Efficiency can also be written in terms of power (the energy per second):
Efficiency equation in terms of power
Worked example
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Examiner Tip
Efficiency can be in a ratio or percentage format. If the question asks for an efficiency as a ratio, give your answer as a fraction or decimal. If the answer is required as a percentage, remember to multiply the ratio by 100 to convert it, e.g. Ratio = 0.25, Percentage = 0.25 × 100 = 25 %