Magnetic Fields

Activities to try

1. 1

   Map the field with a plotting compass

   Why it works: The field is a continuous region of force filling the space all around the magnet, not something that exists only at the poles or only where a line is drawn; the compass and filings merely PROBE it. Direction and strength are two readings of one invisible field.

   1. Place a plotting compass far from any magnet and note that it settles pointing north.
   2. Position a bar magnet, then move the compass step-by-step to many positions around it; at each position draw a small arrow pointing the way the needle's NORTH-SEEKING end points — this is the field direction, running outward from the magnet's north pole toward its south pole.
   3. Join the arrows to trace continuous field lines, working outward from one pole and around to the other.
   4. Deliberately place the compass out to the SIDE of the magnet (not just near the poles) and record which way the needle points compared with when the magnet was absent. Near the magnet the needle lines up with the magnet's field, but with some magnet orientations that direction can match its original northward direction, so also try turning the magnet.
   5. Overlay or compare an iron-filings pattern on the same magnet, noting that filings show shape/strength while the compass shows direction — two readings of one field.
2. 2

   Draw, predict and apply the field-line rules

   Why it works: Field-line drawing is a precise skill governed by rules (continuous, arrowed north→south, never crossing, spacing = strength), and the learner can predict a compass's behaviour from the field rather than treating it as a passive pointer.

   1. Trace a field line through a marked point on a bar-magnet diagram, and at several marked positions draw the direction a compass needle would point.
   2. Predict which way a compass will swing when placed at a given point near the magnet, then check against a plotted pattern.
   3. Decide whether drawn field lines obey the rules: Do any cross? Do they carry arrows? Does spacing show strength?
   4. Label the poles of a magnet from an unlabelled field pattern.
   5. Predict-and-explain (predict, observe, explain): a compass far from magnets points north; predict what happens as a bar magnet is brought alongside it, and WHY, before testing.
3. 3

   Earth as a magnet and the compass for navigation

   Why it works: A compass works because the needle is itself a small magnet that aligns with Earth's magnetic field (when away from other magnets and iron), which is why the same end consistently points (magnetic) north and the compass can be used for navigation.

   1. Draw the Earth as a bar magnet with a compass needle aligning to its field.
   2. Explain why a compass needle's SAME end always turns to point north, in terms of the needle being a tiny magnet aligning with Earth's field.
   3. Reason about transfer: if you took the compass to Australia, would the same end still point north? Why?
   4. Discuss the enrichment point: the Earth's magnetic pole near geographic north behaves like a magnetic south-type pole, so the needle's north pole is attracted to it (opposites attract) — flagged as enrichment, not required.