Magnetic fields — AQA GCSE Physics
Test yourself on Magnetic fields with AQA GCSE practice questions.
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Magnetic fields explained
Direction needs a convention, and this is it: the direction of the magnetic field at a point is the direction of the force that would act on a north pole placed at that point.
Read the full explanation
The practical version is a plotting compass, whose north seeking pole is free to turn; it settles along the field, so the needle points the way the field points. That is why arrows are put on field lines, and the arrows on a field line diagram represent the direction of the field, not its strength. At any point on a curved line the field direction is along the line, in the sense the arrow shows, so a compass placed anywhere on that line lies as a tangent to it.
Your focus
- Explain why every arrow on a field line diagram reverses when the magnet is turned end for end.
- Explain what the arrows drawn on magnetic field lines represent.
- Use a compass reading to state the direction of the field at a marked point.
Magnetic fields exam tips
Marking Points
- one mark for stating that the field direction is the direction of the force on a north pole placed at that point
- one mark for stating that the arrows on field lines represent the direction of the magnetic field
- one mark for stating that the north seeking pole of a compass needle lines up with the field direction
- one mark for reading off the field direction at a marked point from a field diagram
Examiner Tips
- 💡Quote the convention using a north pole, since that is what the specification states.
- 💡If a question asks what the arrows represent, the one word answer is direction.
- 💡Use a compass as the practical way to find the direction at a point.
Common Mistakes
- defining the direction using the force on a south pole
- saying the arrows on field lines show the strength of the field
- drawing field lines with no arrowheads at all
- assuming the field points towards the magnet everywhere around it