Magnetic Field Lines Simulator (2D)

Magnetization

Strength 60%

Field Lines

Line count 28

Iron Filings

Filing count 260

Magnets

Add second magnet

Magnet gap 2.6

Single dipole active · N↔S

Live Readout

Dipole moment

1.00

Field lines drawn

Iron filings

260

Probe field |B|

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How it works

A bar magnet is a magnetic dipole: field lines leave the N pole, arc through space, and re-enter at S, forming closed loops that never actually terminate. This simulator computes the exact planar dipole field B = (3(m·r̂)r̂ − m) / r³ at every point, so field strength falls off as the inverse cube of distance from the magnet — drop back to twice the distance and the field is eight times weaker.

Iron filings are tiny ferromagnetic slivers with no memory of their own: each one simply rotates to align its long axis with the local field direction, which is exactly how a real iron-filing experiment reveals invisible field lines on a sheet of paper. The compass probe works the same way, just drawn as a needle instead of a sliver.

Drag the magnet to reposition it and watch the whole field recompute live. Add a second magnet to see attraction (opposite poles facing) or repulsion (like poles facing) reshape the combined field — the readout reports total dipole moment and live probe strength at any point you click.

Drag the magnet to move it · Click empty space to drop a compass probe