GCSE Physics – Efficiency

Last updated: 26/05/2020
WJEC GCSE Science – Double science foundation Generating electricity GCSE Physics – Efficiency

Learning Objectives

-I can describe why a system might not be 100% efficient
-I can describe ways to increase the efficiency of a system
-I can use, rearrange and recall the units needed for efficiency = useful energy out / total energy in
-I can use, rearrange and recall the units needed for efficiency = useful power out / total power in

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  1. Current
  2. Review
  3. Answered

  1. Can energy be transferred in a system?

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  2. What does a closed system mean?

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  3. What is the net energy change of a closed system?

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  4. How can efficiency be written?

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  5. What is the equation for efficiency?

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  6. What is the equation for efficiency?

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  7. What are the units for efficiency?

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  8. What is the equation to find the useful power out?

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  9. What are the units for power?

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  10. What is the maximum possible efficiency?

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  11. Why might a system not be 100% efficient?

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  12. What type of energy is gravitational potential energy converted to when an object falls?

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  13. What energy is wasted in a kettle?

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  14. What energy is a wasted form in a light?

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  15. What energy is a wasted form in a car’s brakes?

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  16. What type of energy is wasted in all electrical appliances?

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  17. Useful energy out is 400 J and total energy in is 8000 J. What is the efficiency?

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  18. Useful energy out is 56 J and total energy in is 160 J. What is the efficiency?

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  19. Useful energy out is 1.2 x 106 J and total energy in is 4.8 x 107 J. What is the efficiency?

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  20. If power in is 50 W and efficiency is 20%, what is useful power out?

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  21. If power in is 120 W and efficiency is 34%, what is useful power out?

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  22. If power in is 100 W and efficiency is 40%, what is useful power out?

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  23. How does lubrication improve efficiency?

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  24. How does insulation improve efficiency?

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  25. How can a building be warmed up?

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