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Charge and field: OCR A‑Level Physics B questions

Every OCR A-Level Physics B exam question on 6.1.2 Charge and field, 2016–2025, with its mark scheme and examiner’s report.

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1,881 questions

  1. Q23

    June 2025 · Paper 1

    1 mark6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 1, question 23: Which quantity gives the strength of an electric field around an isolated charge? A The area under a graph of electric field versus distance B The area under a

  2. Q40(a)(i)

    June 2025 · Paper 1

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 1, question 40(a)(i): The electrons in the beam are accelerated through a potential difference V. When they enter the magnetic field of flux density B they follow a circular path of

  3. Q40(a)(ii)

    June 2025 · Paper 1

    3 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 1, question 40(a)(ii): Fig. 40.2 shows the path of the electron beam on the fluorescent screen when the magnetic field is produced by the coils. Fig. 40.2 y x The radius of the circul

  4. Q40(b)(i)

    June 2025 · Paper 1

    3 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 1, question 40(b)(i): Use data for the oil drop when it is falling. [3]

  5. Q40(b)(ii)

    June 2025 · Paper 1

    3 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 1, question 40(b)(ii): Calculate the charge on the oil drop. Use data for the oil drop when it is stationary. charge = C [3]

  6. Q2(a)(ii)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 2(a)(ii): A free electron in air travels about 700 nm between collisions with molecules. Use your answer to (a)(i) to calculate the strength of a uniform electric field r

  7. Q2(a)(iii)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 2(a)(iii): Explain why the number of ions formed per second will initially rise at increasing rate after the first ionisation event. [2]

  8. Q2(b)(i)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 2(b)(i): Draw field lines linking the points on the bottom of the cloud marked A to E to points of zero potential. [2]

  9. Q2(b)(ii)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 2(b)(ii): State and explain where the force on free electrons will be the greatest in the region between the zero potential surface and the lower edge of the cloud. [2]

  10. Q5(b)(i)

    June 2025 · Paper 2

    3 marks6.1.2 Charge and field5.1.2 Out into space
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(i): Calculate the ratio of the force due to the electric field (electrostatic force) between a proton and an electron and the gravitational force between the same p

  11. Q5(b)(ii)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(ii): State why gravity is the dominant force in the large‑scale structure of the Universe even though it is weaker than the electrostatic force on an atomic level. [

  12. Q5(c)(i)

    June 2025 · Paper 2

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 2, question 5(c)(i): Calculate the centripetal acceleration of an electron orbiting a proton at a separation of 0.5 × 10–10 m. centripetal acceleration = m s–2 [2]

  13. Q2(d)

    June 2025 · Paper 3

    3 marks6.1.2 Charge and field
    The whole paper ↗
    June 2025 Paper 3, question 2(d): Another method to measure magnetic field strength is to use a Hall probe. A small current passes through a slice of semiconductor material as represented in Fig

  14. Q40(a)(i)

    June 2024 · Paper 1

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2024 Paper 1, question 40(a)(i): Show that the speed of the electrons when they enter the magnetic field is about 1.9 × 107 m s–1. Ignore relativistic effects. [2]

  15. Q40(a)(ii)

    June 2024 · Paper 1

    4 marks6.1.2 Charge and field
    The whole paper ↗
    June 2024 Paper 1, question 40(a)(ii): Describe the path followed by the electron beam when it is passing through the region of magnetic field. You may add to Fig. 40.1 in your description. Include c

  16. Q40(b)

    June 2024 · Paper 1

    2 marks6.1.2 Charge and field
    The whole paper ↗
    June 2024 Paper 1, question 40(b): Fig. 40.2 shows the same experiment when two vertical metal plates are positioned parallel to the initial velocity of the electron. A potential difference is ap

  17. Q40(c)

    June 2024 · Paper 1

    4 marks6.1.2 Charge and field
    The whole paper ↗
    June 2024 Paper 1, question 40(c): The same equipment is used to accelerate negative ions through a potential difference of 1.0 kV. With the same magnetic field, a potential difference of 120 V i

  18. Q6

    June 2023 · Paper 1

    1 mark6.1.2 Charge and field
    The whole paper ↗
    June 2023 Paper 1, question 6: Two parallel conducting plates P and Q have a p.d. V between them. They are separated by distance d. + V 0 V d P Q Which graph shows the variation of electric f

  19. Q29

    June 2023 · Paper 1

    1 mark6.1.2 Charge and field
    The whole paper ↗
    June 2023 Paper 1, question 29: An electron is at a distance of 2.0 × 10–10 m from a proton. Point X is separated from each particle by 1.0 × 10–10 m. 1.0 × 10–10 m 1.0 × 10–10 m X proton elec

  20. Q30

    June 2023 · Paper 1

    1 mark6.1.2 Charge and field
    The whole paper ↗
    June 2023 Paper 1, question 30: An electron travelling at 8.5 × 106 m s–1 enters a uniform magnetic field of flux density 0.57 mT. r What is the radius r of the circular path of the electron i
All 79 questions on Charge and field, as a list
  1. June 2025, Paper 1, Q23 (1 mark): Which quantity gives the strength of an electric field around an isolated charge? A The area under a graph of electric field versus distance B The area under a
  2. June 2025, Paper 1, Q40(a)(i) (2 marks): The electrons in the beam are accelerated through a potential difference V. When they enter the magnetic field of flux density B they follow a circular path of
  3. June 2025, Paper 1, Q40(a)(ii) (3 marks): Fig. 40.2 shows the path of the electron beam on the fluorescent screen when the magnetic field is produced by the coils. Fig. 40.2 y x The radius of the circul
  4. June 2025, Paper 1, Q40(b)(i) (3 marks): Use data for the oil drop when it is falling. [3]
  5. June 2025, Paper 1, Q40(b)(ii) (3 marks): Calculate the charge on the oil drop. Use data for the oil drop when it is stationary. charge = C [3]
  6. June 2025, Paper 2, Q2(a)(ii) (2 marks): A free electron in air travels about 700 nm between collisions with molecules. Use your answer to (a)(i) to calculate the strength of a uniform electric field r
  7. June 2025, Paper 2, Q2(a)(iii) (2 marks): Explain why the number of ions formed per second will initially rise at increasing rate after the first ionisation event. [2]
  8. June 2025, Paper 2, Q2(b)(i) (2 marks): Draw field lines linking the points on the bottom of the cloud marked A to E to points of zero potential. [2]
  9. June 2025, Paper 2, Q2(b)(ii) (2 marks): State and explain where the force on free electrons will be the greatest in the region between the zero potential surface and the lower edge of the cloud. [2]
  10. June 2025, Paper 2, Q5(b)(i) (3 marks): Calculate the ratio of the force due to the electric field (electrostatic force) between a proton and an electron and the gravitational force between the same p
  11. June 2025, Paper 2, Q5(b)(ii) (2 marks): State why gravity is the dominant force in the large‑scale structure of the Universe even though it is weaker than the electrostatic force on an atomic level. [
  12. June 2025, Paper 2, Q5(c)(i) (2 marks): Calculate the centripetal acceleration of an electron orbiting a proton at a separation of 0.5 × 10–10 m. centripetal acceleration = m s–2 [2]
  13. June 2025, Paper 3, Q2(d) (3 marks): Another method to measure magnetic field strength is to use a Hall probe. A small current passes through a slice of semiconductor material as represented in Fig
  14. June 2024, Paper 1, Q40(a)(i) (2 marks): Show that the speed of the electrons when they enter the magnetic field is about 1.9 × 107 m s–1. Ignore relativistic effects. [2]
  15. June 2024, Paper 1, Q40(a)(ii) (4 marks): Describe the path followed by the electron beam when it is passing through the region of magnetic field. You may add to Fig. 40.1 in your description. Include c
  16. June 2024, Paper 1, Q40(b) (2 marks): Fig. 40.2 shows the same experiment when two vertical metal plates are positioned parallel to the initial velocity of the electron. A potential difference is ap
  17. June 2024, Paper 1, Q40(c) (4 marks): The same equipment is used to accelerate negative ions through a potential difference of 1.0 kV. With the same magnetic field, a potential difference of 120 V i
  18. June 2023, Paper 1, Q6 (1 mark): Two parallel conducting plates P and Q have a p.d. V between them. They are separated by distance d. + V 0 V d P Q Which graph shows the variation of electric f
  19. June 2023, Paper 1, Q29 (1 mark): An electron is at a distance of 2.0 × 10–10 m from a proton. Point X is separated from each particle by 1.0 × 10–10 m. 1.0 × 10–10 m 1.0 × 10–10 m X proton elec
  20. June 2023, Paper 1, Q30 (1 mark): An electron travelling at 8.5 × 106 m s–1 enters a uniform magnetic field of flux density 0.57 mT. r What is the radius r of the circular path of the electron i
  21. June 2023, Paper 1, Q35(b) (2 marks): Explain why the acceleration of the alpha particle is greatest at position A. [2]
  22. June 2023, Paper 2, Q4(c)(iii) (2 marks): Calculate the potential energy of an electron at a distance of 1.2 × 10–10 m from a proton. potential energy = J [2]
  23. June 2022, Paper 1, Q19 (1 mark): Which feature represents the magnitude of electrical field strength at a point? Your answer [1]
  24. June 2022, Paper 1, Q20 (1 mark): Which feature represents a change in electrical potential between two points? Your answer [1]
  25. June 2022, Paper 1, Q26 (1 mark): The diagram shows a point X at displacement r from a single point charge +q. The electric field strength at X is E. +q X r A charge of –2q is brought to the sam
  26. June 2022, Paper 1, Q35(a) (2 marks): Use the data in the table to show that 1 electric field strength ∝ (distance from centre of charge)2 Explain your method. Explanation: [2]
  27. June 2022, Paper 1, Q35(b) (2 marks): Explain why the electric potential due to the charged sphere decreases more gradually with distance from the sphere than the decrease of electric field strength
  28. June 2022, Paper 2, Q1(c)(i) (2 marks): Draw six lines on Fig. 1.2 to represent the uniform field between the plates. Assume that the oil drop does not distort the field. [2]
  29. June 2022, Paper 2, Q1(c)(ii) (2 marks): The drop of mass 1.8 × 10–15 kg is held stationary between the plates when the p.d.V between the plates is 200 V. The plate separation is 5.4 mm. Calculate the
  30. June 2022, Paper 2, Q1(c)(iii) (2 marks): When Millikan and Fletcher performed this experiment with many oil drops, they found that the charge on the drop was always a multiple of about 1.6 × 10–19 C (t
  31. June 2022, Paper 2, Q8(b)(i) (2 marks): The article states that the charged particles in the solar wind ‘spiral down the magnetic field near the poles’. Consider an electron in the solar wind moving w
  32. June 2022, Paper 2, Q8(b)(ii) (4 marks): Consider the situation represented in Fig. 8.2. An electron is travelling at 5.0 × 105 m s–1 at an angle of 25° to the direction of the magnetic field of streng
  33. June 2022, Paper 2, Q8(b)(iii) (2 marks): Suggest and explain how the spiral might change as the electron moves nearer to the pole, considering the strengthening field and the energy transferred to part
  34. June 2022, Paper 2, Q9 (6 marks): 9* This question is about the slow rate of fusion in the Sun (lines 33 – 47). The temperature of the core of the Sun is 1.5 × 107 K. Assuming that two protons n
  35. November 2021, Paper 1, Q38(a)(i) (2 marks): Show by calculation that E is about 1 × 1012 V m–1 at distance 40 × 10–12 m from the centre of the proton. [2]
  36. November 2021, Paper 1, Q38(a)(ii) (2 marks): Fig. 38.1 shows the electric field strength E near to a proton. 1.0 E / ×1012 V m–1 0.8 0.6 0.4 0.2 0.0 0 20 40 60 80 100 120 140 160 r / pm Fig. 38.1 Use any t
  37. November 2021, Paper 1, Q38(a)(iii) (2 marks): State what the area under the graph between two r values represents and make an estimate of its value between the marked r values 52 and 160 pm. Area represents
  38. November 2021, Paper 1, Q38(b)(i) (1 mark): Show that the kinetic energy of the electron in orbit is k e2 2r where k is the electric force constant = 1 / 4πεo. [1]
  39. November 2021, Paper 1, Q38(b)(ii) (2 marks): Fig. 38.3 shows the variation of kinetic energy and potential energy of the electron with the radius of its orbit r. 20 energy / eV 10 kinetic energy 0 potentia
  40. November 2021, Paper 1, Q38(b)(iv) (2 marks): In Bohr’s quantised model the radius of orbit for the ground state of the electron (lowest total energy) is given by the equation: ε 0h 2 r = π m e 2 where m an
  41. November 2021, Paper 2, Q1(a)(iii) (1 mark): Explain why electrical potential can be positive or negative. [1]
  42. November 2020, Paper 1, Q19 (1 mark): There are similarities and differences between electric charges, fields and potentials and gravitational masses, fields and potentials. Which one of the followi
  43. November 2020, Paper 1, Q22 (1 mark): The speed of an alpha particle is 8 times the speed of a beta particle. They both travel through a 0.3 T uniform magnetic field perpendicular to their path. for
  44. November 2020, Paper 1, Q42(a)(i) (1 mark): Draw on Fig. 42.1 above the equipotential line at + 8.0 V. [1] potential / V 12 0 A B displacement Fig. 42.2
  45. November 2020, Paper 1, Q42(a)(ii) (1 mark): Draw on Fig. 42.2 a line which shows how the potential varies along the field line AB. [1]
  46. November 2020, Paper 1, Q42(a)(iii) (1 mark): The distance AB is 5.0 mm. Calculate the electric field between the plates. electric field = V m−1 [1]
  47. November 2020, Paper 1, Q42(b)(i) (2 marks): Use data from Fig. 42.4 to show that the value of the velocity of the electron when accelerated through the potential difference Va is greater than 1 × 106 m s−
  48. November 2020, Paper 2, Q9(a) (3 marks): A doubly-charged carbon-14 atom is accelerated through a potential difference of 4.2 MV and enters a uniform magnetic field of strength 0.72 T. Use the equation
  49. November 2020, Paper 2, Q9(b) (2 marks): Explain why it is important to ensure that no 12CH2 2+ and 13CH+ ions reach the second deflecting magnet (See Fig. 6 in the Advance Notice Article). [2]
  50. June 2019, Paper 1, Q12 (1 mark): A positive and a negative charge of equal magnitude are placed near each other. Which diagram best represents the electric field of the two charges? A B – – + +
  51. June 2019, Paper 1, Q13 (1 mark): Two horizontal metal plates are 5.0 mm apart. The plates are at potentials of + 120 V and + 40 V. + 120 V 5.0 mm + 40 V What is the force experienced by an elec
  52. June 2019, Paper 1, Q37(b)(i) (2 marks): To estimate the temperature at which 2H and 3H nuclei will fuse, a student writes down the formula: e2 4πε0R ≈ k T Explain what the two sides of the approximati
  53. June 2019, Paper 1, Q37(b)(ii) (1 mark): Use the equation in (b)(i) to estimate this temperature when R ≈ 2 × 10−14 m. temperature = K [1]
  54. June 2019, Paper 2, Q4(a)(i) (2 marks): An electron is accelerated through a p.d. of 4.3 kV. Calculate the velocity of the accelerated electron. Ignore relativistic effects. velocity = m s–1 [2]
  55. June 2019, Paper 2, Q6(a) (1 mark): State how Fig. 6.2 shows that the electric field is uniform within the selector. [1]
  56. June 2019, Paper 2, Q6(b)(i) (2 marks): By considering the forces on the charge, explain why the charge will not be deflected when v = Es . Bs [2]
  57. June 2019, Paper 2, Q6(b)(ii) (2 marks): Show that the units of magnetic field strength are equivalent to the unit of velocity. [2]
  58. June 2019, Paper 2, Q6(b)(iii) (3 marks): Describe and explain the motion of charges moving through the region if their velocities are not equal to Es . Bs [3]
  59. June 2019, Paper 2, Q6(c)(i) (1 mark): Show that the force on a proton moving at a velocity of 5.2 × 106 m s–1 at right angles to a field of strength 0.64 T is about 5.3 × 10–13 N. [1]
  60. June 2019, Paper 2, Q6(c)(ii) (2 marks): Calculate the radius r of the path the proton will follow. radius = m [2]
  61. June 2019, Paper 2, Q6(c)(iii) (3 marks): A beam of 12 6C and 14 6C singly charged positive ions with equal velocities enters a deflection region, travelling at right angles to a uniform magnetic field
  62. June 2018, Paper 1, Q20 (1 mark): Which expression gives the time for the particle to complete one circle of its motion? 2r m A Bqr 2r mr B Bq 2r m C Bq Bq D 2r m Your answer [1]
  63. June 2018, Paper 1, Q21 (1 mark): A proton and an α particle, with the same velocity, enter the region of constant magnetic flux density. r What is the ratio of the radii of their paths, ? a rpr
  64. June 2018, Paper 1, Q29 (1 mark): The electric potential at a distance r from a positive point charge Q is 450 V. The potential increases to 500 V when the distance from the point charge decreas
  65. June 2018, Paper 1, Q37(b)(i) (2 marks): A positive ion of charge Q and mass m is accelerated through a p.d. V. Show that the p it gains is given by the expression momentum per unit mass m p c m. Q 2 V
  66. June 2018, Paper 1, Q37(b)(ii) (2 marks): Discuss an advantage of using ions of hydrogen 1H+ as propellant instead of xenon 130Xe+. [2]
  67. June 2018, Paper 1, Q41(a)(i) (1 mark): Explain why the electric field strength at X is zero. [1]
  68. June 2018, Paper 1, Q41(a)(ii) (2 marks): Calculate the electric potential at X. potential = V [2] Question 41 continues on page 35
  69. June 2018, Paper 1, Q41(b)(i) (4 marks): Show that the resultant force F on the third proton is about 4 # 10−10 N in the direction shown. Explain your reasoning. You may include a diagram in your answe
  70. June 2018, Paper 1, Q41(b)(ii) (2 marks): The separation of protons in a lithium the magnitude of the resultant electric force on a proton in the nucleus if the protons are arranged symmetrically as in
  71. June 2018, Paper 3, Q3(b)(i) (2 marks): Calculate the electric field strength E between the two parallel plates. Include a suitable unit. E = …………………. unit ………… [2]
  72. June 2018, Paper 3, Q3(b)(ii) (3 marks): Calculate the charge q carried by each oil drop. q = C [3]
  73. June 2018, Paper 3, Q3(b)(iii) (2 marks): This calculation does not take into account the effect of buoyancy from the displaced air. This effect produces an additional upwards force on the oil drop. Exp
  74. June 2018, Paper 3, Q3(c) (2 marks): The charge on the parallel metal plates is reversed. Explain the effect this has on the motion of the oil drop. [2]
  75. June 2017, Paper 1, Q25 (1 mark): An oil drop of mass m charged by one electron is balanced between two parallel horizontal metal plates. A potential difference V is applied between the plates a
  76. June 2017, Paper 1, Q41(a) (2 marks): On the appropriate figure(s) mark a point • N where the electric field is zero and a point • V [2] where the electric potential is zero.
  77. June 2017, Paper 1, Q41(b) (2 marks): On each of Fig. 41.1 and 41.2 draw three complete equipotential lines. [2]
  78. June 2017, Paper 1, Q41(c) (2 marks): Fig. 41.2 can also represent two spherical charge distributions of +1 C and –1 C situated 1 km apart. Calculate the electric field midway between the charge cen
  79. June 2017, Paper 1, Q41(d) (6 marks): Fig. 41.1 shows the electric field pattern near two protons and Fig. 41.2 the electric field pattern near a proton and an electron. Fig. 41.1 Fig. 41.2 (d)* Fig

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