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IB Physics SL D 2 Electric and Magnetic Fields Questions

Practise IB Physics SL D.2 by analysing charge interactions, charge transfer, electric-field patterns and uniform plate fields, alongside magnetic field-line direction.

Syllabus
First assessment 2025
Course
Physics SL
Level
SL

Exam points

  • Use Coulomb’s law to calculate forces between point charges and determine whether the charges attract or repel.
  • Apply conservation of charge to determine an unknown charge in a particle reaction.
  • Use grounding and induction to infer electron redistribution and the conductor’s net charge.
  • Calculate E=F/q or the point-charge field, then combine field vectors from multiple charges.
  • Use F=qE and Newton’s second law to calculate a charged particle’s acceleration or describe its motion.
  • Read electric-field lines for direction and charge arrangement, and compare field strength from their density.
  • Calculate the uniform field between parallel plates with E=V/d using their potential difference and separation.
  • Draw magnetic-field lines around a current-carrying wire and infer their direction from current.

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 lines

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 SL

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 SL

Outline why the ions are likely to spread out.

Question 2

[Maximum number: 8]

This question is in two parts. Part 1 is about simple harmonic motion and forced oscillations. Part 2 is about electric and magnetic force fields.

Part 1 Simple harmonic motion and forced oscillations
The graph shows the variation with time of the displacement of an object undergoing simple harmonic motion.
displacement / mm

Figure for Question 2 — IB Physics SL

time / ms

Question (a)

(a)

Part 2 Electric and magnetic force fields

[ 8 ]

Question (i)

(i)

Define electric field strength.

[ 2 ]

Question (ii)

(ii)

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

Figure for Question (ii) — IB Physics SL
[ 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 (iii)

(iii)

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 (iii) — IB Physics SL
[ 2 ]

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 3

[Maximum number: 1]

The diagram shows a junction in a circuit.

Figure for Question 3 — IB Physics SL

The currents in the three wires are related by I1=I2+I3I_{1}=I_{2}+I_{3}.
State the fundamental law of Physics from which this relation is derived.

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