Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Describe the shape and direction of the magnetic field around bar magnets…
Full specification wording
Topic 12 – Magnetism and the motor effect: 12.4 Describe the shape and direction of the magnetic field around bar magnets and for a uniform field, and relate the strength of the field to the concentration of lines
Field lines map a magnetic field.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 4 of 13
Study notes
From the checked teaching notes for this specification point.
The idea
Field lines map a magnetic field. Around a bar magnet they leave the north pole and enter the south pole, curving round from north to south outside the magnet. The lines never cross. Close to a pole the lines are crowded together, showing a strong field; further away they spread out, showing a weaker field. Between two facing opposite poles the lines run almost straight and parallel from north to south, giving a uniform field of constant strength and direction. Between two facing like poles the lines curve away from each other, leaving a region where the field is weak. A plotting compass placed in the field points along the field line, with its north pole indicating the field direction.
What earns the marks
- States that magnetic field lines around a bar magnet run from the north pole to the south pole outside the magnet.
- Describes the field between two facing opposite poles as uniform, with parallel, equally spaced lines of constant strength and direction.
- Relates a high concentration of field lines to a strong field and widely spaced lines to a weak field.
- Describes the field pattern between two facing like poles as lines curving away from each other with a weak region between them.
Common mistakes and how to put them right
Draws field lines running from south to north outside the magnet.
Put it right by drawing them from north to south outside the magnet.
Shows field lines crossing one another.
Put it right by keeping every line separate, since field lines never cross.
Treats widely spaced lines as indicating a strong field.
Put it right by linking crowded lines to strength and spread-out lines to weakness.
Exam tips
- Check the arrow direction on every field line you draw or select, since direction is part of the description.
- Use spacing as the visual cue for strength: crowded means strong, spread out means weak.
- Recognise the parallel, evenly spaced pattern as the signature of a uniform field between opposite poles.
Try the lesson
The start of the Topic 12 – Magnetism and the motor effect: 12.4 Describe the shape and direction of the magnetic field around bar magnets and for a uniform field, and relate the strength of the field to the concentration of lines lesson, made from checked teaching notes for this specification point.
Have a go first
In which direction do magnetic field lines point around a bar magnet?
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