4.5

4.5

· 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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Consider a kettle:
1) Wasted Heat: 400 J, Heat to Water: 1000 J, Sound Energy: 600 J
2) Efficiency = (Useful Eout/Total Ein)x100 = (1000/2000)x100 = 50%

Consider a computer:
1) 150 - (20 + 10) = 120 J
2) Efficiency = (Useful Eout/Total Ein)x100 = (120/150)x100 = 80%

Sankey Diagrams.ppt Download this file

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4.4

efficiency = useful energy output

                                                        total energy input

Version 1

Efficiency = Useful E_out / Total E_in x 100

Useful E_out = Useful Energy Out ( J )

Total E_in = Total Energy In ( J )

Efficiency = Efficiency ( % )

Version 2

Efficiency = Useful E_out / Total E_in

Useful E_out = Useful Energy Out ( J )

Total E_in = Total Energy In ( J )

Efficiency = Efficiency ( No Units; a number between 0 and 1 )

4.3

Energy is conserved

1) Energy in = Chemical Potential Energy, Energy out = Kinetic Energy

2) Energy in = Elastic Potential Energy, Energy out = Kinetic Energy

3) Energy in = Chemical Potential Energy, Energy out = Heat and Light Energy

4) Energy in = Elastic Potential Energy, Energy out = Kinetic Energy

4.2

9 Types of Energy:

• Chemical Potential Energy
• KE (Kinetic Energy)
• Light
• Sound
• Thermal
• GPE (Gravitational Potential Energy)
• Elastic Potential Energy
• Electrical
• Nuclear

- Potential: means that the energy is stored.

Energy transfer diagrams:

Scientific Facts I Need To Remember For Next Time*

• Remember that the law of reflection is: angle i = angle r (angle of incidence is the same as the angle of reflection)
• Remember that the potential difference is: the supply voltage (overall voltage in the circuit)  minus the voltage of the bulb
• Read the questions more carefully
• An ammeter does not affect the size of the current, the battery affects the size of the voltage