Lesson 3.7.5.5

3.7.5.5 Alternating currents Quiz: AQA Physics, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.7.5.5, Alternating currents: 20 multiple choice questions for the AQA Physics (7408), Unit 7: Fields and their consequences (A-level only), written with Revision Ninja.

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The 20 questions

  1. Which value of an alternating current equals the direct current giving identical heating power?

    • Peak value
    • Mean value
    • Root mean square
    • Peak-to-peak value

  2. For a sinusoidal current with peak value I0, which expression gives the rms current?

    • I0 x sqrt(2)
    • I0 / sqrt(2)
    • 2 I0 / pi
    • I0 / 2

  3. How is the peak-to-peak voltage of a sinusoidal ac signal determined from its peak voltage?

    • Half peak voltage
    • Twice peak voltage
    • Root two times peak
    • Equal to peak voltage

  4. The mains supply in the UK has an rms voltage of 230 V. What is its peak voltage?

    • 460 V
    • 163 V
    • 325 V
    • 230 V

  5. The mains supply has an rms voltage of 230 V. What is its peak-to-peak voltage?

    • 920 V
    • 460 V
    • 325 V
    • 650 V

  6. A sinusoidal current has a peak value of 4.0 A. What is its rms value?

    • 2.8 A
    • 5.7 A
    • 4.0 A
    • 1.4 A

  7. A sinusoidal voltage has an rms value of 12 V. What is its peak value?

    • 24 V
    • 17 V
    • 8.5 V
    • 12 V

  8. A 10 ohm resistor is connected across a sinusoidal supply of rms voltage 12 V. What is the average power dissipated?

    • 28.8 W
    • 7.2 W
    • 14.4 W
    • 1.44 W

  9. An oscilloscope shows one complete cycle of a waveform occupying 20 ms. What is its frequency?

    • 500 Hz
    • 0.050 Hz
    • 20 Hz
    • 50 Hz

  10. On an oscilloscope, one full cycle spans 8.0 divisions at a time base of 5.0 ms per division. What is the frequency?

    • 5 Hz
    • 200 Hz
    • 25 Hz
    • 40 Hz

  11. A sinusoidal source has a peak voltage of 6.0 V and is connected across a 2.0 ohm resistor. What is the average power dissipated?

    • 9.0 W
    • 4.5 W
    • 18 W
    • 36 W

  12. What is the average value of a sinusoidal alternating current over one full cycle?

    • Zero
    • RMS current
    • Peak current
    • Half peak current

  13. A d.c. supply produces the same heating in a resistor as a sinusoidal current of peak value 2.0 A. What is the d.c. current?

    • 1.0 A
    • 2.0 A
    • 1.4 A
    • 2.8 A

  14. A sine wave on an oscilloscope has a period of 4.0 ms. What is its frequency?

    • 4 Hz
    • 250 Hz
    • 500 Hz
    • 125 Hz

  15. Which signal component is blocked when an oscilloscope input is set to AC coupling?

    • AC component
    • DC component
    • High frequency noise
    • Fundamental frequency

  16. A 2.0 kW appliance runs from a 230 V rms mains supply. What is the rms current it draws?

    • 8.7 A
    • 12 A
    • 0.12 A
    • 4.3 A

  17. A 325 V peak supply is across a 100 ohm resistor. What is the average power dissipated?

    • 530 W
    • 3.3 kW
    • 1060 W
    • 265 W

  18. A sine wave has a peak-to-peak value of 10 V. What is its rms value?

    • 5.0 V
    • 3.5 V
    • 2.5 V
    • 7.1 V

  19. Which voltage value is used to calculate the average power dissipated by an alternating current?

    • RMS voltage
    • Mean voltage
    • Peak-to-peak voltage
    • Peak voltage

  20. A 6 V, 3 W lamp runs correctly on an rms supply. What peak voltage is needed for the same brightness on a sine supply?

    • 6.0 V
    • 4.2 V
    • 12 V
    • 8.5 V

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