Bar Magnet Field

This simulation models the magnetic field of a bar magnet as a dipole. Iron filings and compass needles line up along the local field, and field lines loop from the north pole to the south pole. A strength slider runs from 10 to 200 millitesla, and buttons flip the poles or turn the magnet. Readouts show the field at a pole, on the axis and sideways at 6 cm. It suits a lesson on magnetic poles, field lines never crossing or ending, and how the field weakens with distance.

• Press Flip poles and watch every compass needle turn round to follow the new field direction.
• Raise Strength from 80 to 200 mT and compare the Field at pole readout before and after.
• Compare the On axis, 6 cm and Sideways, 6 cm readouts to see the field is stronger along the axis.
• Switch Field lines off to see only the filings, then switch them on again and trace one line from north to south.
• Turn Turn magnet off to hold the magnet still and study one view of the filing pattern.

1. 1Describe the shape of the magnetic field around a bar magnet.
2. 2Explain that field lines leave the north pole, enter the south pole and never end.
3. 3Use compass needles and iron filings to find the direction of a field.
4. 4Compare field strength near the poles with strength further away.

Questions teachers ask