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IB Physics HL D 2 Electric and Magnetic Fields Questions

Practise IB Physics HL D.2 by analysing superposed electric and magnetic fields, potentials, forces and charged-particle trajectories.

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • Combine field, force and potential equations for multi-charge and extended-field problems.
  • Analyse charged-particle motion in crossed or varying fields using vector and energy reasoning.
  • Interpret field maps, flux-related evidence and experimental uncertainty in HL data.

Covered syllabus points

D.2.1—Electric charge forcesD.2.2—Coulomb’s lawD.2.3—Charge conservationD.2.4—Millikan experimentD.2.5—Charge transferD.2.6—Electric field strengthD.2.7—Electric field linesD.2.8—Field-line densityD.2.9—Parallel-plate fieldD.2.10—Magnetic field linesD.2.11 (HL)—Electric potential energyD.2.12 (HL)—Two-charge potential energyD.2.13 (HL)—Electric potential as scalarD.2.14 (HL)—Electric potentialD.2.15 (HL)—Electric potential gradientD.2.16 (HL)—Work in electric fieldsD.2.17 (HL)—Electric equipotentialsD.2.18 (HL)—Equipotentials and electric fields

Question 1

[Maximum number: 2]

Ion-thrust engines can power spacecraft. In this type of engine, ions are created in a chamber and expelled from the spacecraft. The spacecraft is in outer space when the propulsion system is turned on. The spacecraft starts from rest.

Figure for Question 1 — IB Physics HL

The mass of ions ejected each second is 6.6×10−6 kg6.6 \times 10^{-6} \mathrm{~kg} and the speed of each ion is 5.2×104 m s−15.2 \times 10^{4} \mathrm{~m} \mathrm{~s}^{-1}. The initial total mass of the spacecraft and its fuel is 740 kg . Assume that the ions travel away from the spacecraft parallel to its direction of motion.

In practice, the ions leave the spacecraft at a range of angles as shown.

Figure for Question 1 — IB Physics HL

Outline why the ions are likely to spread out.

Question 2

[Maximum number: 10]

This question is in two parts. Part 1 is about photoelectricity. Part 2 is about electrical and magnetic force fields.
Part 1 Photoelectricity

Question (a)

(a)

Define electric field strength.

[ 2 ]

Question (b)

(b)

(b) The diagram shows a pair of horizontal metal plates. Electrons can be deflected vertically using an electric field between the plates.

Figure for Question (b) — IB Physics HL
[ 4 ]

Question (i)

(i)

Draw the shape and direction of the electric field between the plates on the diagram.

[ 2 ]

Question (ii)

(ii)

Calculate the force on an electron between the plates when the electric field strength has a value of 2.5×103NC−12.5 \times 10^{3} \mathrm{NC}^{-1}.

[ 2 ]

Question (c)

(c)

The diagram shows two isolated electrons, X and Y , initially at rest in a vacuum. The initial separation of the electrons is 5.0 mm . The electrons subsequently move apart in the directions shown.

Figure for Question (c) — IB Physics HL
[ 4 ]

Question (i)

(i)

Show that the initial electric force acting on each electron due to the other electron is approximately 9×10−24 N9 \times 10^{-24} \mathrm{~N}.

[ 2 ]

Question (ii)

(ii)

The diagram shows Y as seen from X , at one instant. Y is moving into the plane of the paper. For this instant, draw on the diagram the shape and direction of the magnetic field produced by Y .

[ 2 ]

Question 3

[Maximum number: 1]

Deuterium, 12H{ }_{1}^{2} \mathrm{H}, undergoes fusion according to the following reaction.

12H+12H→13H+X{ }_{1}^{2} \mathrm{H}+{ }_{1}^{2} \mathrm{H} \rightarrow{ }_{1}^{3} \mathrm{H}+\mathrm{X}

Particle Y is produced in the collision of a proton with a K−\mathrm{K}^{-}in the following reaction.

K−+p+→K0+K++Y\mathrm{K}^{-}+\mathrm{p}^{+} \rightarrow \mathrm{K}^{0}+\mathrm{K}^{+}+\mathrm{Y}

The quark content of some of the particles involved are

K−=u‾ s K0=d s‾\mathrm{K}^{-}=\overline{\mathrm{u}} \mathrm{~s} \quad \mathrm{~K}^{0}=\mathrm{d} \overline{\mathrm{~s}}

Identify, for particle Y , the

charge.

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