Lesson 3.7.3.1

3.7.3.1 Coulomb's law Quiz: AQA Physics, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.7.3.1, Coulomb's law: 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. Coulomb's law gives the force between two point charges in a vacuum as:

    • F = Q1 Q2 r^2 / (4 pi eps0)
    • F = Q1 Q2 / (4 pi eps0 r^2)
    • F = Q1 Q2 / (4 pi eps0 r)
    • F = 4 pi eps0 Q1 Q2 / r^2

  2. The permittivity of free space, eps0, has a value of approximately:

    • 9.11 x 10^-31 kg
    • 1.60 x 10^-19 C
    • 8.85 x 10^-12 F m^-1
    • 6.67 x 10^-11 N m^2 kg^-2

  3. Between point charges, like charges:

    • all attract
    • all repel
    • attract and unlike charges repel
    • repel and unlike charges attract

  4. Unlike gravitational forces, electrostatic forces between charges can be:

    • always attractive
    • zero between like charges only
    • attractive or repulsive
    • always repulsive

  5. The electrostatic force between two point charges is inversely proportional to:

    • the separation
    • the square root of their separation
    • the square of their separation
    • the cube of their separation

  6. For a charged sphere, the charge may be considered to be located:

    • evenly spread through its volume at all distances
    • only on its surface, giving zero force at the centre
    • at its nearest surface point
    • at its centre, for points outside the sphere

  7. For calculating the force between charges, air can be treated as a vacuum because:

    • air is a perfect conductor
    • its relative permittivity is very close to 1
    • air has zero permittivity
    • air has infinite permittivity

  8. Two point charges of 2.0 microcoulomb and 3.0 microcoulomb are 0.10 m apart in a vacuum. What is the force between them?

    • 54 N
    • 0.54 N
    • 5.4 N
    • 0.0054 N

  9. What is the electrostatic force between an electron and a proton separated by 5.3 x 10^-11 m? Take e = 1.6 x 10^-19 C.

    • about 2.3 x 10^-28 N
    • about 8.2 x 10^-6 N
    • about 8.2 x 10^-10 N
    • about 8.2 x 10^-8 N

  10. The ratio of electrostatic to gravitational force between an electron and a proton is roughly:

    • 10^-39
    • 10^3
    • 10^39
    • 10^12

  11. Two like point charges of 1.0 microcoulomb each are 1.0 m apart in a vacuum. What is the force between them?

    • 9 x 10^3 N
    • 9 x 10^-3 N
    • 9 x 10^-6 N
    • 9 x 10^-9 N

  12. Two equal positive point charges are a distance d apart. The net electrostatic force on a charge placed at the midpoint is:

    • four times the force from one charge
    • zero, since the two forces are equal and opposite
    • twice the force from one charge
    • equal to the force from one charge

  13. A charge Q1 and charge Q2 are separated by r and experience force F. If Q1 is doubled and r is halved, the new force is:

    • 2F
    • 4F
    • F/8
    • 8F

  14. The forces two point charges exert on each other are:

    • equal in magnitude and opposite in direction
    • equal in magnitude and in the same direction
    • zero
    • unequal, with the larger charge exerting the greater force

  15. The constant 1 / (4 pi eps0) in Coulomb's law is approximately:

    • 9.0 x 10^9 N m^2 C^-2
    • 1.60 x 10^-19 N m^2 C^-2
    • 8.85 x 10^-12 N m^2 C^-2
    • 6.67 x 10^-11 N m^2 kg^-2

  16. When the separation between two point charges is tripled, the electrostatic force becomes:

    • one sixth
    • one third
    • one twelfth
    • one ninth

  17. Charges of +4.0 microcoulomb and +1.0 microcoulomb are 0.30 m apart. At what point on the line between them is the net force zero?

    • 0.15 m from the 4.0 microcoulomb charge
    • 0.25 m from the 4.0 microcoulomb charge
    • 0.10 m from the 4.0 microcoulomb charge
    • 0.20 m from the 4.0 microcoulomb charge

  18. Two protons are separated by 1.0 x 10^-15 m. Estimate the electrostatic force between them, with e = 1.6 x 10^-19 C.

    • about 2300 N
    • about 2.3 N
    • about 230 N
    • about 0.23 N

  19. A student says gravity is negligible between two electrons because they have no charge, so no force acts. Which response is best?

    • Incorrect: gravity is stronger than electrostatic force between electrons.
    • Incorrect: gravity acts between the masses regardless of charge, but it is far weaker than their electrostatic repulsion.
    • Correct: gravity acts only between charged particles.
    • Correct: electrons attract gravitationally only when charged.

  20. An electron orbits a proton in a circle of radius 5.3 x 10^-11 m, with the electrostatic force providing the centripetal force. Estimate its speed (m_e = 9.11 x 10^-31 kg).

    • about 1.1 x 10^3 m s^-1
    • about 4.4 x 10^6 m s^-1
    • about 2.2 x 10^4 m s^-1
    • about 2.2 x 10^6 m s^-1

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