Objective 4.5

 Kettle

10 squares = 2000J/s therefore 1 square = 200J/s

Wasted Heat = 2 squares = 400J/s

Useful Heat = 5 squares = 1000J/s

Wasted sound = 3 squares = 600J/s

 

Efficiency = Useful E_out / Total E_in x 100

Efficiency = 1000 / 2000 x 100

Efficiency = 50%

 

Computer

Conservation of energy so…

Total E_in = Total E_out

150J = 20 + 10 + Useful E_out

Useful E_out = 120J

 

Efficiency = Useful E_out / Total E_in x 100

Efficiency = 120 / 150 x 100

Efficiency = 80%

4.5

10 June 2011

11:42

·         4.5 describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship (see 4.4), including their representation by Sankey diagrams

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