Efficiency Examples in Physics
Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Efficiency.
This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.
Concept Recap
The ratio of useful output energy (or power) to total input energy, expressed as a percentage — always less than 100% due to energy losses.
What fraction of the energy you put in actually goes where you want it to go, rather than being wasted as heat.
Read the full concept explanation →How to Use These Examples
- Read the first worked example with the solution open so the structure is clear.
- Try the practice problems before revealing each solution.
- Use the related concepts and background knowledge badges if you feel stuck.
What to Focus On
Core idea: Efficiency can never exceed 100%—you can't get more out than you put in.
Common stuck point: High efficiency doesn't mean low power use—it means less waste.
Sense of Study hint: When solving an efficiency problem, first identify the useful energy output and the total energy input. Then divide useful output by total input and multiply by 100 to get a percentage. If given power instead of energy, the formula is the same: \eta = P_{\text{out}} / P_{\text{in}} \times 100\%.
Worked Examples
Example 1
easySolution
- 1 Use the efficiency formula: \eta = \frac{\text{useful output}}{\text{total input}} \times 100\%.
- 2 Substitute the given values: \eta = \frac{350}{500} \times 100\%.
- 3 \eta = 70\%
Answer
Example 2
mediumPractice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
mediumExample 2
hardBackground Knowledge
These ideas may be useful before you work through the harder examples.