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Science and Technology K–6 · Year 4

How far away does a magnet start to pull? Reach on a ruler

Science understanding: Physical sciences

PracticalLow risk

The idea

A magnet's pull acts at a distance and gets rapidly stronger as the gap closes, so the distance at which a paper clip jumps is a fair way to compare magnets and to test poles.

What you need

  • 3 different magnets: ferrite bar, horseshoe, fridge magnet
  • steel paper clips
  • a 30 cm ruler taped flat to the bench
  • a smooth sheet of paper on the bench so the clip slides easily
  • recording table

How to do it

  1. Tape the ruler down and place the bar magnet with one pole at the zero mark.
  2. Put a paper clip at 10 cm and slide it toward the magnet one millimetre at a time until it jumps to the magnet. Record the distance where it jumped.
  3. Repeat five times and take the mean.
  4. Turn the magnet to present the other pole and repeat, then present the middle of the long side of the magnet and repeat.
  5. Repeat for the horseshoe and fridge magnets.
  6. Rank the magnets by reach and describe where on each magnet the pull is strongest.

What you should see

The clip jumps from a few millimetres to a few centimetres depending on the magnet; the two poles of a bar magnet give about the same reach and the middle of the side gives a much shorter one, so the force is concentrated at the poles. The fridge magnet has the shortest reach. Five trials scatter, so the mean is reported with the range; the ranking of the three magnets is the finding.

What changes

What you change
magnet and which part faces the clip
What you measure
distance at which the clip jumps
What you keep the same
  • same clip
  • same paper surface
  • same sliding speed

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • A bigger magnet is always stronger.
  • The middle of a bar magnet pulls as hard as the ends.
  • Magnets pull only when touching.

Safety card

Low riskLearners carry it out

Hazards

  • pinched fingers between magnets

Controls

  • one magnet on the bench at a time
  • no neodymium magnets

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST2-9PW-STST2-1WS-S
  • Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST2-DAT-01
  • Australian Curriculum v9AC9S4U03AC9S4I02AC9S4I03AC9S4I05

Sources

The pages the author read to write this activity.

  1. www.scootle.edu.au/ec/search?accContentId=AC9S4U03
  2. curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
  3. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
  4. primaryconnections.org.au/v84-sequences/magnetic-moves
  5. spark.iop.org/experiments-magnets

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