AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The direction of the magnetic field at any point is given by the direction…
Full specification wording
Magnetic fields: The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.
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.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 6
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
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. 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.
What earns the marks
- Stating that the field direction is the direction of the force on a north pole placed at that point.
- Stating that the arrows on field lines represent the direction of the magnetic field.
- Stating that the north seeking pole of a compass needle lines up with the field direction.
- Reading off the field direction at a marked point from a field diagram.
Common mistakes and how to put them right
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.
Exam tips
- 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.
Try the lesson
The start of the Magnetic fields: The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point. lesson, made from checked teaching notes for this specification point.
Have a go first
A small north pole is placed at a point in a magnetic field. What does the direction of the force on this north pole tell you?
Listen
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. 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. A strong answer earns marks for these points. stating that the field direction is the direction of the force on a north pole placed at that point. stating that the arrows on field lines represent the direction of the magnetic field. stating that the north seeking pole of a compass needle lines up with the field direction. reading off the field direction at a marked point from a field diagram. Exam tip: If a question asks what the arrows represent, the one word answer is direction.
See it
Key words
Say what each word means before you turn the card.
direction of a field
Try answering aloud or in your head before turning the card.
arrows on field lines
Try answering aloud or in your head before turning the card.
plotting compass
Try answering aloud or in your head before turning the card.
See every definition
- direction of a field
- The direction of the force that would act on another north pole placed at that point.
- arrows on field lines
- These represent the direction of the magnetic field, not its strength.
- plotting compass
- Its north seeking pole is free to turn and settles along the field, so the needle points the way the field points.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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