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Core · Practice questions · Magnetic fields

Lines, direction, and strength.

Six original Cambridge-style questions on magnetic fields: what a field is, the direction and rules for field lines, reading strength from their spacing, and plotting a field with a compass.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
The rules examiners look for

From north, to south, never crossing.

01
Recall
[2 marks]

State what is meant by a magnetic field, and state how the direction of the field at a point is defined.

  • A magnetic field is the region around a magnet where a magnetic force acts. ✓
  • Its direction at a point is the direction of the force on a north pole there (the way a compass north end points). ✓
02
Recall
[3 marks]

State three rules that must be followed when drawing the magnetic field lines around a bar magnet.

  • Lines point from the north pole to the south pole outside the magnet. ✓
  • Lines never cross one another. ✓
  • Lines are closer together where the field is stronger (near the poles). ✓
03
Application
[2 marks]

A bar magnet has its north pole on the left. A plotting compass is placed directly above the middle of the magnet. State the direction in which the red north-seeking end of the compass points, and give a reason.

It points to the right, toward the south pole. ✓

Above the magnet the field runs from the north pole round to the south pole, and the needle lines up with the field. ✓

04
Application
[3 marks]

Describe how a small plotting compass can be used to plot one magnetic field line around a bar magnet.

  • Place the compass near the magnet and mark a dot at each end of the needle. ✓
  • Move the compass so the tail sits on the last dot, and mark the new tip. Repeat across the paper. ✓
  • Join the dots with a smooth line and add an arrow pointing from N to S. ✓
05
Analysis
[2 marks]

On a field diagram, the lines are drawn much closer together near the poles than in the middle of the sides. State what this spacing tells you, and explain why the lines are never drawn crossing.

  • Closer lines show that the field is stronger there, so the field is strongest near the poles. ✓
  • The lines never cross because the field has a single direction at each point, so a compass there can only point one way. ✓
06
Analysis
[2 marks]

A student draws field lines around a bar magnet with the arrows pointing from the south pole to the north pole, outside the magnet. State what is wrong, and give the correct rule.

  • The arrows are reversed. ✓
  • Outside the magnet, field lines point from the north pole to the south pole. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.