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Efficiency

9th grade (Year 10 in England) · 16 questions · Common Core: NGSS.HS-PS3-3 · England: KS4 Combined Science: Energy

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  1. Question 1

    A device is supplied with 2500 J and transfers 1875 J usefully. What is its efficiency, as a percentage?

    Answer%

  2. Question 2

    Why do LED bulbs save money compared with old filament bulbs?

    • A. They are more efficient, so less energy is wasted as heat
    • B. They are brighter because they are hotter
    • C. They are made of glass
    • D. They use no electricity

  3. Question 3

    A motor is 85% efficient. It is supplied with 3000 J. How much useful energy does it transfer, in J?

    AnswerJ

  4. Question 4

    A device is supplied with 1000 J and transfers 750 J usefully. What is its efficiency, as a percentage?

    Answer%

  5. Question 5

    Why do LED bulbs save money compared with old filament bulbs?

    • A. They are made of glass
    • B. They are brighter because they are hotter
    • C. They use no electricity
    • D. They are more efficient, so less energy is wasted as heat

  6. Question 6

    A motor is 30% efficient. It is supplied with 1000 J. How much useful energy does it transfer, in J?

    AnswerJ

  7. Question 7

    A device is supplied with 200 J and transfers 160 J usefully. What is its efficiency, as a percentage?

    Answer%

  8. Question 8

    Why do LED bulbs save money compared with old filament bulbs?

    • A. They are made of glass
    • B. They are more efficient, so less energy is wasted as heat
    • C. They are brighter because they are hotter
    • D. They use no electricity

  9. Question 9

    A motor is 30% efficient. It is supplied with 500 J. How much useful energy does it transfer, in J?

    AnswerJ

  10. Question 10

    A device is supplied with 1000 J and transfers 250 J usefully. What is its efficiency, as a percentage?

    Answer%

  11. Question 11

    An electric motor is 80% efficient. What happens to the other 20%?

    • A. It is mostly wasted heating the motor and its surroundings
    • B. It is turned into extra motion
    • C. It is destroyed
    • D. It is stored in the plug

  12. Question 12

    A motor is 90% efficient. It is supplied with 3000 J. How much useful energy does it transfer, in J?

    AnswerJ

  13. Question 13

    A device is supplied with 400 J and transfers 360 J usefully. What is its efficiency, as a percentage?

    Answer%

  14. Question 14

    How can a house be made more energy efficient?

    • A. open all the windows in winter
    • B. use thinner walls
    • C. add loft insulation and double glazing
    • D. remove the curtains

  15. Question 15

    A motor is 35% efficient. It is supplied with 1000 J. How much useful energy does it transfer, in J?

    AnswerJ

  16. Question 16

    A device is supplied with 1000 J and transfers 100 J usefully. What is its efficiency, as a percentage?

    Answer%

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Answer key: Efficiency

  1. 1. 75 %

  2. 2. A. They are more efficient, so less energy is wasted as heat

  3. 3. 2550 J

  4. 4. 75 %

  5. 5. D. They are more efficient, so less energy is wasted as heat

  6. 6. 300 J

  7. 7. 80 %

  8. 8. B. They are more efficient, so less energy is wasted as heat

  9. 9. 150 J

  10. 10. 25 %

  11. 11. A. It is mostly wasted heating the motor and its surroundings

  12. 12. 2700 J

  13. 13. 90 %

  14. 14. C. add loft insulation and double glazing

  15. 15. 350 J

  16. 16. 10 %