Electricity and Magnetism

Drawing magnetic field patterns

Teaching Guidance for 11-14 Supporting Physics Teaching

Spotting the pattern

Thinking about the teaching

Our experience over many years of directing pupils to scatter iron filings around bar magnets has shown that the magnetic field patterns which seem so clear to us are far from obvious to the vast majority of pupils. Indeed how else could it be? This is one of those situations where:

… if you know what you are looking for, it's obvious

… if you don't know what you are looking for, it's hopeless!

We have a physics teacher friend who remembers teaching a year 8 class about magnetic fields. The pupils were drawing the magnetic field pattern around a bar magnet, using iron filings, and our friend looked over the shoulder of one of the pupils. The boy was producing a drawing that was heavy with shading and, in some ways, captured what was in front of him, but that displayed nothing of the magnetic field pattern which the teacher actually wanted. The teacher pointed at the boy's drawing and then at the actual pattern of iron filings, and said:

Teacher: John, just look at the iron filings and look at your drawing! Does it look anything like that? Are you looking at the same thing as me?

As soon as he had said this, our teacher friend smiled to himself. The point could not have been more clear. The teacher and pupil were looking at different things. The teacher saw a magnetic field pattern, the pupil saw clumps of iron filings. Before the pupil could draw the field pattern he needed more instruction in what it was that he was looking out for.

There is an important message for teaching here.

Teacher Tip: Guide pupils as to what to see: don't expect what is obvious to you to be obvious to them.

can be analysed using Magnetic Field
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