1. 20 October 2010 2.5 Efficiency What are the three types of heat transfer. Which states of matter do they work in?
2. Aims Understand the efficiency of energy transformations Calculate efficiency from given data
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4. Efficiency Often a lot of the energy that goes into a system is wasted, mainly as heat To save energy and money, manufacturers are developing appliances that make better use of energy and therefore waste less We describe these as energy efficient
6. Worked example The energy input per second to a desk lamp with a standard tungsten filament is 100 J and the output is 5 J. Energy expressed as joules per second is the power, which has the unit of watts (W). How efficient is the lamp?
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8. Activity A: Write down the ways in which a petrol engine wastes energy
9. Activity B: what is the efficiency of a lamp if the useful energy given out each second is 60 J with 100 J of energy put it.
10. Saving our worlds resources Our sources of energy can be separated into renewable and non-renewable Renewable can be replaced, non-renewable cannot.
