Plenary Questions 4.2 to 4.5

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Plenary Questions 4.2 to 4.5

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Plenary Questions 42 to 45.one Download this file

4.5

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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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45.one Download this file

Answers
Kettle
1) Wasted heat = 400 J
Heat to water= 1000J
Sound energy= 600J

2)
Useful Energy output / Useful Energy input X 100
1000/2000 X 100 = 50%

Computer
1) 150 - 20 - 10 = 120J
2)Useful Energy output / Useful Energy input X 100
120/150 X 100 = 80%

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Objective 4.4

Version 1

Efficiency = Useful Eout / Total Ein X 100

Useful Eout = Useful energy output (J)
Total Ein = Total energy input (J)
Efficiency = Efficiency (%)

Version 2
Efficiency = Useful Eout / Total Ein

Useful Eout = Useful energy output (J)

Total Ein = Total energy input (J)

Efficiency = Efficiency ( no units; a number between 0 and 1)