Efficiency
Slides in this set (3)
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- Useful energy output isn't usually equal to total energy input
- This is because no device is 100% efficient - apart from electric heaters (normally)
- Wasted energy is usually transferred to "useless" thermal energy stores
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- Efficiency = Useful output energy / Total input energy
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- Example:
- 30J of energy is supplied to a kettle. 22.5J of energy are transferred to the thermal energy store of the water. Work out the efficiency of the kettle giving your answer as a percentage.
- Efficiency = Useful output energy / Total input energy
- Efficiency = 22.5 / 30
- Efficiency = 75%