Lesson 3.7.4.2

3.7.4.2 Parallel plate capacitor Quiz: AQA Physics, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.7.4.2, Parallel plate capacitor: 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 formula gives the capacitance of a parallel-plate capacitor?

    • C = ε0 εr A / d
    • C = A d / (ε0 εr)
    • C = ε0 εr A d
    • C = ε0 εr d / A

  2. What is the unit for relative permittivity of a dielectric material?

    • Coulombs per volt
    • Unitless
    • Farads per metre
    • Farads

  3. A parallel-plate capacitor in air has plate area 0.020 m^2 and plate separation 2.0 mm. Taking epsilon0 = 8.85 x 10^-12 F m^-1, what is its capacitance?

    • 8.85 pF
    • 88.5 pF
    • 885 pF
    • 8.85 nF

  4. The same capacitor, with the same geometry, is now filled with a dielectric of relative permittivity 4. What is its capacitance?

    • 1420 pF
    • 88.5 pF
    • 22.1 pF
    • 354 pF

  5. What is the value of the permittivity of free space, epsilon0?

    • 8.85 x 10^12 F m^-1
    • 1.26 x 10^-6 F m^-1
    • 4.00 x 10^-7 F m^-1
    • 8.85 x 10^-12 F m^-1

  6. How do polar molecules in a dielectric respond when an electric field is applied?

    • They rotate
    • They expand rapidly
    • They vibrate randomly
    • They ionise completely

  7. What happens to capacitance if the plate area of a parallel-plate capacitor is doubled?

    • It doubles
    • It halves
    • It remains unchanged
    • It quadruples

  8. A parallel-plate capacitor has its plate area doubled and its plate separation halved. By what factor does its capacitance change, with air between the plates?

    • 1 time, so unchanged
    • 8 times
    • 2 times
    • 4 times

  9. A capacitor has capacitance 10 pF in air. The gap is then filled with a dielectric of relative permittivity 2.5, geometry unchanged. What is the new capacitance?

    • 12.5 pF
    • 4 pF
    • 25 pF
    • 40 pF

  10. Which graph of capacitance C against plate separation d gives a straight line through the origin?

    • C against sqrt(d)
    • C against d
    • C against 1/d
    • C against d^2

  11. A parallel-plate capacitor in air has plate area 100 cm^2 and separation 0.50 mm. What is its capacitance?

    • 1.77 nF
    • 354 pF
    • 17.7 pF
    • 177 pF

  12. A capacitor is connected to a fixed voltage supply. If relative permittivity increases, what happens to stored charge?

    • Halves
    • Decreases
    • Stays the same
    • Increases

  13. A parallel-plate capacitor has plate area 0.05 m^2, separation 1.0 mm and dielectric relative permittivity 3. It is charged to 100 V. What charge is stored?

    • 1.33 x 10^-9 C
    • 4.43 x 10^-10 C
    • 4.43 x 10^-8 C
    • 1.33 x 10^-7 C

  14. A 300 V supply is connected across an air-filled parallel-plate capacitor with a 3.0 mm gap. What is the electric field strength between the plates?

    • 1.0 x 10^6 V m^-1
    • 1.0 x 10^5 V m^-1
    • 9.0 x 10^4 V m^-1
    • 1.0 x 10^4 V m^-1

  15. An isolated charged capacitor has a dielectric with relative permittivity 4 inserted. What happens to potential difference?

    • Quadrupled
    • Unchanged
    • Halved
    • Quartered

  16. A 1.0 m^2 parallel-plate capacitor in air has plates 1.0 mm apart. Which value is closest to its capacitance?

    • about 9 pF
    • about 9 nF
    • about 90 nF
    • about 9 uF

  17. A parallel-plate capacitor with air between its plates has a 1.0 cm gap. The dielectric strength of air is 3.0 x 10^6 V m^-1. What is the maximum pd before breakdown?

    • 30 kV
    • 300 V
    • 300 kV
    • 3 kV

  18. A capacitor at fixed voltage has relative permittivity increased by factor 6. How does stored energy change?

    • Increases thirtysixfold
    • Increases sixfold
    • Remains unchanged
    • Decreases sixfold

  19. A 50 pF air-filled capacitor has plate separation 0.40 mm. What separation gives a capacitance of 100 pF with the same plate area?

    • 0.80 mm
    • 0.40 mm
    • 0.20 mm
    • 0.10 mm

  20. Which change to a parallel-plate capacitor results in the largest capacitance?

    • Halved separation, halved permittivity
    • Halved separation, tripled permittivity
    • Doubled area, doubled separation
    • Doubled separation, tripled permittivity

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