Lesson 6.2.4.3

6.2.4.3 The National Grid Quiz: AQA Combined Science, Unit 19

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.2.4.3, The National Grid: 20 multiple choice questions for the AQA GCSE Combined Science (8464), Unit 19: Electricity, written with Revision Ninja.

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The 20 questions

  1. What components make up the National Grid system?

    • Batteries and resistors
    • Switches and fuses
    • Motors and generators
    • Cables and transformers

  2. What is the function of step-up transformers in the National Grid?

    • Increase current
    • Increase potential difference
    • Decrease potential difference
    • Decrease frequency

  3. What is the function of step-down transformers in the National Grid?

    • Decrease resistance
    • Decrease potential difference
    • Increase potential difference
    • Increase current

  4. Why do transmission cables use a high potential difference?

    • Lower cable cost
    • Increase current flow
    • Reduce heating losses
    • Speed up electrons

  5. Which component raises the potential difference before electricity is transmitted?

    • Step-up transformer
    • Fuse
    • Step-down transformer
    • Resistor

  6. Why is the National Grid an efficient way to transfer energy?

    • High current speed
    • Zero wire resistance
    • Low current heating
    • Direct current use

  7. What type of electrical supply do transformers operate with?

    • Alternating current
    • Chemical cell
    • Direct current
    • Static charge

  8. What does a step-down transformer achieve in the National Grid?

    • Maximum grid voltage
    • Constant direct current
    • Increased transmission speed
    • Safe domestic voltage

  9. Higher tier: a transformer has a primary potential difference of 230 V with a current of 2 A. The secondary potential difference is 23 V. What is the secondary current, assuming no energy loss?

    • 0.2 A
    • 20 A
    • 200 A
    • 2 A

  10. If transmission potential difference increases tenfold at constant power, how does current change?

    • Hundred times smaller
    • Ten times bigger
    • Ten times smaller
    • Stays unchanged

  11. How many times greater is power loss when current increases tenfold?

    • Thousand times
    • One hundred times
    • Ten times
    • Two times

  12. A cable of resistance 0.5 ohms carries 20 A. What power is wasted as heat in the cable?

    • 10 W
    • 400 W
    • 200 W
    • 20 W

  13. Which change reduces the current in power transmission lines for a fixed power?

    • Increase potential difference
    • Increase resistance
    • Decrease potential difference
    • Decrease frequency

  14. A cable of resistance 3 ohms carries 2 A for 60 s. How much energy is lost as heat?

    • 12 J
    • 720 J
    • 360 J
    • 2160 J

  15. What happens to the total power in an ideal transformer?

    • It decreases
    • It increases
    • It becomes zero
    • It remains constant

  16. A transmission line carries 240 kW at 240 kV. What current flows?

    • 1 A
    • 1000 A
    • 240 A
    • 0.001 A

  17. A current of 200 A flows through a cable of resistance 0.01 ohms. What power is lost as heat?

    • 2 W
    • 20 W
    • 400 W
    • 4000 W

  18. Higher tier: a transformer has a primary coil of 5 V and 0.4 A, and a secondary coil of 50 V. What is the secondary current, assuming no energy loss?

    • 0.4 A
    • 0.04 A
    • 4 A
    • 0.0004 A

  19. Higher tier: a step-up transformer has a secondary potential difference of 10 kV and a secondary current of 2 A. The primary potential difference is 500 V. What is the primary current, assuming no energy loss?

    • 4 A
    • 0.4 A
    • 400 A
    • 40 A

  20. Which two factors determine power loss as heat in a transmission cable?

    • Current and resistance
    • Length and voltage
    • Voltage and current
    • Mass and resistance

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