Visualising magnetic fields in three dimensions
Purpose
In year 8 pupils build on their basic knowledge of magnets from primary school and are introduced to electromagnets.
All pupils will have seen the shape of a bar magnets magnetic field using iron filings sprinkled on a piece of paper with a magnet placed below. Unfortunately this does not demonstrate the 3 dimensional nature of the magnetic field and therefore makes it more difficult for pupils to visualise the magnetic field around objects such as the Earth.
Ferrofluid
We have used a liquid called Ferrofluid available from scuddlebutt3.co.uk which enables students to ‘see’ the three dimensional shape of the magnetic field. The common misconception that magnetic fields are flat 2 dimensional shapes is quickly removed as soon as pupils are able to see the ferro fluid take the shape of the surrounding field.
Magnetic field round a bar magnet
Ferrofluid is a viscous liquid which can be poured into a beaker. About 5 cm3 should be used so that it covers the bottom of a small beaker. A bar magnet can then be placed under the bottom of the beaker.
In a magnetic field ferrofluid becomes very viscous almost solid in nature and takes the shape of the magnetic field. By rotataing the bar magnet the shape of magnetic field appears at the poles and along the side. It also illustrates how the density of the field lines varied with the distance from the magnet.
Magnetic field round a wire
Due to the versatile nature of ferrofluid, it was also possible to show the magnetic field around a straight wire and a coil; something that normally requires a plotting compass and a lot of imagination.
Again it is simply poured into a beaker and the beaker is placed over the wire or coil. Students can very clearly see that an electric current produces a magnetic field around the wire. The strength of the magnetic field can be varied by coiling the wire and students can easily see this effect using the Ferrofluid.
Last updated: 4 June 2007
