Lesson 6.1.2.2

6.1.2.2 Efficiency Quiz: AQA Combined Science, Unit 18

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.2.2, Efficiency: 20 multiple choice questions for the AQA GCSE Combined Science (8464), Unit 18: Energy, written with Revision Ninja.

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The 20 questions

  1. What is the numerator in the efficiency equation using energy?

    • Wasted energy output
    • Useful energy output
    • Total energy input
    • Useful energy input

  2. What is the denominator in the efficiency equation using power?

    • Maximum power limit
    • Total power input
    • Useful power output
    • Wasted power output

  3. In what format can energy efficiency values be correctly expressed?

    • Only as fractions
    • Only as decimals
    • Only as percentages
    • Decimal or percentage

  4. What is the maximum possible efficiency value for any real device?

    • 50%
    • 100%
    • Infinite
    • 200%

  5. Which quantity is the numerator in the energy efficiency equation?

    • Useful output energy
    • Useful power input
    • Wasted output energy
    • Total input energy

  6. What is the standard SI unit of energy efficiency?

    • Watts
    • Percentages
    • Joules
    • No unit

  7. Which device typically has the lowest energy efficiency?

    • Step-up transformer
    • Electric heater
    • LED lamp
    • Filament bulb

  8. A burner heats a beaker of water. What is the total energy input?

    • Thermal energy
    • Kinetic energy
    • Chemical energy
    • Electrical energy

  9. A motor takes 500 J electrically and gives 400 J of useful work. What is its efficiency?

    • 20%
    • 125%
    • 500%
    • 80%

  10. A device has 1200 W input and 300 W useful output. What is its efficiency as a decimal?

    • 0.25
    • 0.75
    • 0.025
    • 4

  11. A lamp is 8% efficient and has 100 W input. How much useful light power does it give?

    • 92 W
    • 12.5 W
    • 80 W
    • 8 W

  12. A machine is 60% efficient and takes in 2000 J. How much useful output does it give?

    • 3333 J
    • 1200 J
    • 2000 J
    • 800 J

  13. A transformer is 90% efficient and its input is 1000 W. How much power is wasted?

    • 900 W
    • 100 W
    • 1000 W
    • 10 W

  14. An efficiency calculation yields 1.2. What does this indicate?

    • Calculation error
    • 120% efficient
    • 100% efficient
    • Superconductor

  15. Device A is 70% efficient with 500 J input. Device B is 85% efficient with 400 J input. Which gives more useful output?

    • Device A, 350 J against 340 J
    • Both give 340 J
    • Device B, 340 J against 350 J
    • Both give 350 J

  16. A device's efficiency rises from 40% to 50% with the same input of 600 J. How much more useful energy is output?

    • 120 J
    • 240 J
    • 60 J
    • 30 J

  17. Which method increases the efficiency of a machine?

    • Reducing friction
    • Increasing resistance
    • Adding mass
    • Increasing input

  18. A machine's useful power is 400 W and its efficiency is 80%. What is its total input power?

    • 320 W
    • 400 W
    • 480 W
    • 500 W

  19. Why can efficiency never exceed 100 percent?

    • Power is constant
    • Conservation of energy
    • Friction creates energy
    • Energy is created

  20. How is 0.35 written as a percentage?

    • 35%
    • 0.35%
    • 350%
    • 3.5%

All AQA Combined Science quizzes