This document discusses the efficiency of energy transformations and calculations. It defines efficiency as the ratio of useful energy output to total energy input. An example is provided where a desk lamp with 100J input and 5J output has an efficiency of 5%. The document also mentions the three types of heat transfer that work across different states of matter and encourages activities to identify energy waste and calculate efficiency from input/output data.

1. 20 October 20102.5 EfficiencyWhat are the three types of heat transfer. Which states of matter do they work in?

2. AimsUnderstand the efficiency of energy transformationsCalculate efficiency from given data

4. EfficiencyOften a lot of the energy that goes into a system is wasted, mainly as heatTo save energy and money, manufacturers are developing appliances that make better use of energy and therefore waste lessWe describe these as energy efficient

5. Efficiency equation

6. Worked exampleThe 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?

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 resourcesOur sources of energy can be separated into renewable and non-renewableRenewable can be replaced, non-renewable cannot.

13. Assessment activity 2.5See sheet