Science 7–10 · Year 7

Mapping the field around a bar magnet with iron filings and a plotting compass

Physical sciences — Forces, content group Magnets in everyday life (NSW Stage 4 focus area; ACARA places magnetic forces in Year 4, AC9S4U03, and has no Year 7 to 10 content description on magnetism, so only Year 7 inquiry codes are cited)

PracticalLow risk

The idea

A magnet exerts a non-contact force through the space around it, and the pattern of that field can be drawn as lines running from north pole to south pole that are closest where the field is strongest.

What you need

bar magnets, 2
iron filings in a shaker, 1
A4 paper or clear acrylic sheet, 2
plotting compass, 1
steel paperclip, 1
sharp pencil, 1
tray to catch filings, 1

How to do it

Place one bar magnet under a sheet of paper on the tray. Shake filings lightly over the sheet and tap the paper gently until the filings settle into a pattern. Sketch the pattern, then tip the filings back into the shaker.
Place the magnet on a fresh sheet and draw round it. Put the plotting compass near the north pole, mark a dot at the tip of the needle, move the compass so its tail sits on the dot and mark again. Continue until the line reaches the south pole or runs off the page.
Repeat from at least eight starting points around the magnet to build the field map. Add arrows showing the direction the compass north end points.
Place two magnets in line with unlike poles 3 cm apart under a new sheet and map with filings; then repeat with like poles facing and compare the two patterns.
Note where the filings are thickest and relate this to where a paperclip is pulled hardest.

What you should see

Filings form curved lines looping from one pole to the other and cluster densely at the poles. Plotted compass lines run from the north pole round to the south pole and never cross. Unlike poles show lines running straight across the gap; like poles show lines pushed apart with a clear region between them. The learner knows it worked when the compass map and the filings pattern have the same shape.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

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

Field lines are real threads in the space around the magnet.
The field exists only at the poles.
Two north poles attract.

Safety card

Low riskLearners carry it out

Hazards

iron filings in eyes or cuts
filings sticking to the magnet

Controls

keep paper between magnet and filings
wash hands after use
use a tray

Note

No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.

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 7–10 Syllabus (2023)SC4-FOR-01 SC4-WS-01 SC4-WS-05
Australian Curriculum v9AC9S7I04

Sources

The pages the author read to write this activity.

All Concept Studio activities