Define a magnetic field through the force on a pole
Describe the region around a magnet using a test pole and distinguish a field model from a material substance.
Core and Extended; Physics 0625, 2026–2028. Follow the selected magnetism or charge section. Field lines are explanatory models, not material threads or measured force values. Written practice is self-checked.
Before you begin
- Name magnetic poles.
- Distinguish forces on separate ends of a test magnet.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What can a force do to a freely supported object?
What you will learn
- Define a magnetic field as a region where a magnetic pole experiences a force.
- Interpret a turning test magnet without requiring contact.
Describe a region of influence
A magnetic field is a region in which a magnetic pole experiences a force. A magnet can therefore affect another magnetic object across a gap. The field description identifies the influence at locations in space; it is not a flow of iron filings from one magnet to another.
A small test magnet contains both north and south poles. Their forces can turn it into alignment. Turning is evidence of interaction even if there is little net translation. Talking about a test pole does not mean an isolated single magnetic pole has been manufactured.
Represent without confusing the representation
Field lines help show the pattern and direction. The lines are a drawing convention, not physical threads that must be touched by a pole before a force acts. A pole placed between two drawn lines can still experience the field.
A line diagram by itself does not give a force in newtons. Quantitative strength needs additional calibrated information. In this section, identify the field's meaning and direction before attempting to compare its relative strength.
Pause and explain
Which description defines a magnetic field?
Worked example
A small magnet turns near a larger magnet without touching it. Explain this using a field.
Show the worked solution
- The larger magnet produces a magnetic field.
- The test magnet's poles experience forces.
- Those forces can turn the test magnet.
Answer The test magnet interacts with the field; contact is not needed.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State the magnetic-field definition.
Give me a hint
Name both the region and the appropriate test object.
Compare my reasoning
- Consider a region in space.
- Place a magnetic pole there in the model.
- It experiences a magnetic force.
A region in which a magnetic pole experiences a force.
Look for these in your work
- Include force.
- Specify a magnetic pole.
Why can a small magnet turn even when its centre hardly moves?
Give me a hint
Consider forces on its separate poles.
Compare my reasoning
- The magnet has north and south ends.
- Forces on those ends can produce a turning effect.
- Rotation need not require large net translation.
The pole forces can turn the magnet without large translation.
Look for these in your work
- Include both poles.
- Separate turning from movement of the centre.
A learner says a pole between drawn field lines has zero magnetic force. Evaluate the claim.
Give me a hint
Distinguish the continuous field from a limited set of drawn representative lines.
Compare my reasoning
- The lines represent the field pattern.
- They are not physical tracks.
- A test pole can interact between the drawn lines.
The claim confuses the representation with the field occupying the region.
Look for these in your work
- Explain what lines represent.
- Do not infer a zero force from blank paper.
Common mistakes
- Field lines are representations.
- A test magnet has both poles.
- Turning and translation are different observations.
What can you explain now?
Can a pole experience a field between two drawn lines?
Compare with the explanation
Yes.
The field occupies the region; the drawing does not restrict it to literal threads.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Define a field operationally and explain what a field-line drawing does and does not show.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.